The Mechanism of A Magnetic Motor Starter

Many people have no knowledge concerning electrical equipment present in our machines, especially those which are embedded inside and cannot be seen such as a magnetic motor starter. Maybe one day you asked yourself a question similar to this one, “what is a working mechanism of magnetic motor starter?”

Meaning of the magnetic motor starter.

This is an electromagnetic operating switch which is used to prevent the electric motor when you turn it on. It can be used in heavy-duty systems and industries like 3 phase large motors. It offers below-voltage and above voltage protection and it is capable of cutting off if there is an electric failure.

This device is a union of a contactor and an overload relay. If it is open and there is a detection of an overload, a magnetic motor starter will allow the control voltage and starter coil. If they are designed to be used in heat unstable conditions, then a device called a “heater” is installed in the overload relay. The heater has two metal elements that fix all legs of the motor. If your machine is functioning, then the currents pass through the heater. If the amount of power passing through the heater is large than the rated amount of the heater, the heater will become very hot leading to the immediate disconnection of the relay. This action interferes contactor coil circuit and reduces the energy of the contact.

We are going to tell you about two types of magnetic motor starter; –

First the full-voltage magnetic motor starter

Most magnetic motor starters are widely available as a full-voltage starter. They are sometimes known as across-the-line, reduced-voltage and reversing magnetic motor starter. This starter uses a full voltage; this means that it is intentionally designed to handle the current as the motor starts.  Reduced-voltage starters are used to reduces the effects of incoming current after the motor starts to run. They are mostly used in electromechanical and electronic systems.

The second is the full- voltage reversing starter

They are made to move back the shaft of a three-phase motor. This is done through the exchange of any two-line conductors which cater the motor load. This type has a forward and backward starter as part of manufacturing. To avoid the concurrent movement of the reverse and forward starter, a design incorporates electrical and mechanical interlocks. This makes sure that a single movement is performed. They are normally useful in wood workshop machinery like cabinet saws and shapers. For tools that use a small load, do not use this, instead, they use a switch only. An example of such tools is a drill press. Magnetic starters are used by many machines and second-hand starters can be purchased to replace or retrofit the old ones.

According to the National Fire Protection Agency standard 7.5.3, it is a must for all machinery to install a magnetic starter to prevent those machines against uncontrolled restarting of the machine for example when power is restored.

Choosing Between The Fusible Or Non-Fusible Safety Switches

If you are concerned about your enterprise, then one of the most important matters to be concerned about is the safety of employees, associates, and appliances. Also when talking about electrical appliances, safety, once shorts and related disasters occur, it is a matter to focus.  This helps to guarantee safety by preventing property and life loss and injury.

To prevent such damages from occurring, then it is important to have a disconnect switch. If you want to install it, you must ask yourself what kind of design should I purchases? Should I buy a fusible or non-fusible switch? Is there any difference between the two?

Follow this post all these questions will be answered clearly.

Meaning of a disconnect switch

These are devices that are installed in order to protect your system against irregular electrical currents. They are also referred to as safety switches or “load break switches”. They function by shutting down the power in the system within a second, immediately once there are power failures, other complications, and uncontrolled activation. You may depend on it to do the disconnection when there are:

  • Emergency and unstable interference of the power
  • High amounts of currents
  • Short-circuits
  • Physical damage to electrical appliances.

They may be used when maintaining, repairing and inspecting while there is “lockout”.

What to choose fusible or non-fusible?

Deciding on the type of switch to purchase depends on the type of equipment that in hand. Apart from that, other external variables can affect your decision. The only method to ensure that your choice will be the best is to work under the supervision of the experienced certified electrician. It is difficult to come with a quick and simple answer to complex and important issues like this. Make sure you decide correctly to secure your business.

After taking a note on the above-explained matter, someone may still propose some generalizations.  Though both switches give access to either open or close the circuit manually, fusible switches are preferred for those systems with higher loads. Most people use non-fusible switches for household appliances such as a water heater. But appliance that has a higher load use a safety switch with relatively higher safety ratings.

What is the meaning of higher safety?

This is a difference in the way how these two switches operate. Both are functions well in the opening and closing circuits, but the fusible switches offer stronger protection than non-fusible switches when it comes to the matter of overcurrent and other electrical accidents. This is achieved due to the usage of many fuses placed in the switches.

We offer the best reliable, designed and dependable switches with high performance.

A Short Explanation Of Electrical Lugs And Its Several Usage

There are so many kinds of wires and connectors that are used in the wiring and electrical industry. They are employed in connection with electrical mechanical assemblies. For example, the electrical lugs which are used for joining electrical appliances. They are more useful once you want to supply and distribute electric current continuously without encountering any obstacle between the electrical cables. They are also used where the permanent joining of cables is impossible.

They are very easy to install, repair and maintain, these advantages do not apply to them only but also to the appliances and cables carrying them. They are widely used to join one cable with another or where there is a joining of many cables. Their use does not end here but also extends to joining socket fuse, load switches, and other electrical devices. There is a specific type of lug that is designed purposefully to handle high voltage cables and electrical appliances. Most lugs are enclosed in rubber or plastic-covered sheets. This is very important for guaranteeing safety during handling.

In most cases, to join a cable to an electrical appliance, one end of the electrical lug is used.  Mostly this end is compressed into small folds or joined using low-melting alloy mainly based on tin and lead or joined to the metal by heating of the surfaces. This has a function of making sure that an established connection is correct and tight. The other side of the lug will be joined to the terminal of the device to be connected. For fixing purposes, a bolt or screw may be used to fix them tightly on the device. Also, a spring clip may be used to connect. There is a difference in the usage of cable lugs depending on the industry in concern.

Due to that, there are different sizes, shapes, materials used in the manufacturing and configuration of cable lugs. The difference in usage depending on the industry concerned could be demonstrated using the following example. There are several types of terminals that could be used, such as blade, hook, fork, pin, and ring in insulated lugs. All these are very useful in wiring and control panel industries. They are used too in automation and instrumentation industries. Ring lugs made of copper are widely used when connecting many cables. Most devices use copper cable lugs.

There is another kind of connector referred to as butt and parallel connector. It is widely used when joining or separating two cables. Another kind is called butt and parallel connector, which is insulated with Poly Vinyl Chloride, shrinks when subjected to heat and is closed at one end. Most industries that use cables to join appliances use this type of connector. It is also designed with several sizes, shapes, and materials. It may be used with Copper cable lug buts it depends on the materials used to join devices.

Another type is tube crimping lugs which are widely used in the power distribution industry. The thick layer for insulation is used in most connectors to help the passage of high voltage electricity. Some people choose to use copper tubular lugs. Usage of lugs will dictate what kind of material to be used for manufacturing lugs.

Lugs are of high necessity in the wiring and electrical industry. Rating of lugs based upon tolerance should be inspected before subjecting them to heavy-duty usages. In most cases, the shape is an additional factor to consider. Choose the lugs depending on usage.

The Major Difference Between a Safety Switch And A Circuit Breaker.

Many experts are using much time to formulate unambiguous definitions, advice on how to ensure safety on your commercial premises. What the motive behind this move? Frankly speaking, nowadays there is a lot of misconceptions going on around. These may lead to huge uncertainty and sometimes risk. In this post, we are going to look at safety switches and circuit breakers.

We are devoted in giving our clients the best products and services. We have best safety switches and circuit breakers. Please call or email us.

How do they differ?

It normal to hear people referring to these products interchangeably, though they perform the same task. It is inappropriate to refer them in such fashion. Though it is common to find them in a single electrical control panel, each has its own function and hence they are different from each other.

A safety switch also referred to as a safety disconnect is monitoring equipment of current electricity incorporated in several systems. They widely used in large equipment systems such as conveyor belts and other large electrical devices. They are also used to protect the entire system of the appliances. A mode of application is simply by checking for any electrical defect and control the current. If there is any defect in the system such as an electric leak, equipment does not respond efficiently or the system has a short then immediately a safety switch will cut off the electricity in the problematic system.

For a case of a circuit breaker, it just controls the overloading of power into a circuit. If a certain circuit is drawing a lot of electricity, then the circuit breaker will disconnect automatically leading to electric shut off. Most people are two familiar circuit breakers because they are found at-home systems. For example, you plug any device with high electric demand into a full capacity circuit, disconnection or trip will occur.

I hope until now you may differentiate between the two.

It may seem that there is only a small difference between the two! And all are incorporated in the power control panel and cuts off the power when there is a problem. But there is a critical difference which is that a circuit breaker is not able to protect the system against an injury. It just looks at the excessive drawing of power into a particular circuit. It has nothing to offer and there is a short-circuit or electric leakage. If you rely only on a circuit breaker, then your system is a risk of encountering potential damages.

The safety switch controls any inconsistencies in the systems such as shorts and leakages and will cut off power if a situation persists.  In nutshell, circuit breakers are for wiring protection while safety switches are for the protection of devices and people at large. Due to this, your business should be given all safety measures to maximize safety in your building.

Utility Connections At Existing Service Entrance Panels

The Meter-Main Combo Panel

They are widely used in most parts of the country. They have a meter socket enclosed in the same case with the main circuit breaker. Some of them consist of a space that can be used to attach load breakers. You are not allowed to use conductors that are exposed from the main breaker present between the socket and the main breaker to supply the PV connection. By doing so you are offending and breaking terms and conditions listed on the manual of the equipment. Those terms and conditions stipulate that all associated equipment should be used according to the instruction and limitations are given.

Sometimes, the producer of the meter main-combo may enclose explanations and hardware to construct a PV connection.  An accredited inspector, from the National, Recognized Testing Laboratory (NRTL) or other authority certified by OSHA and may be needed by the meter producer or the Authority Having Jurisdiction (AHJ).

In some cases, the usages take into consideration the circuit amidst the main breaker and meter socket and no connection is allowed under no condition.

If you have a meter that consists of load breaker space in the case, then a back-fed PV breaker can be installed. Something to note is that the breaker and PV connections are on the load side of the main breaker, making them be load-side connection, thus allowing section 705.12(B) to be used.

In any conventional meter main combo panel, there are similar ratings between the conductor and the main breaker. If you have load breakers and PV breakers connected to such conductor, then section 705.12(B)(2)(3)(b) will come into effect and the back-fed PV breaker should be positioned at the furthest point from the main breaker. Once you have a back-fed PV breaker with 20 amps for a 100-amp conductor, 25 amps for a 125-amp and 40 amps for a 200-amp conductor, then a rule called 120 percent rule will be used.

A general principle here is that, if you take 120% of the conductor’s value then you subtract the main breaker value you will get the maximum value of back-fed breaker. Take an example of a conductor with 200-amp and the main breaker having 200-amp. You will have to compute the following mathematics 1.2 x 200 – 200= 40 amps which are the maximum value of the back-fed breaker.

It is required by the law that for a PV inverter, 125% of the output current to be used for calculations. But this gives a translation of the breaker ratings because the breaker should be at a minimum of 125% of the PV inverter output.

Some producers of meter-main combo panel design these meters with interchangeable breakers. Even if there is a 200-amp conductor or 150-amp conductor a small main breaker may be used as usual. For successful safety, careful inspection and analysis should be done, this should involve the whole building to make sure that the established main breaker is oversize and the main breaker with low ratings may be used for substituting it. Under all these circumstances the manufacturer’s manuals should indicate this. If you use a main breaker with low ratings, you may allow a huger back-fed PV breaker to be used.

Look at the following mathematics. A 300-amp meter main combo panel has allowed 250-amp. 1.2x 300-250= 110 amps. This is a maximum rating to be used for the back-fed PV breaker.

What to do if there is no breaker position.

If that happens then connect it at remote subpanel. If you find out that your meter-main combo panel does not have a position to attach an open load breaker, then two options are solutions. The first solution is to meet all specifications of the meter-main combo panel and subpanel, as stipulated under section 705.12, (B)(2)(3) by making a connection between the load side PV connection and the meter-main combo.

A breaker sending to the subpanel should be located at the furthest point from the main breaker on the conductor. It is necessary to make sure that, this condition also applies to the subpanel. Also, a back-fed PV connector should be located on the furthest point of the conductor as much as possible.  This distance could be either from the main lug or the main breaker of the subpanel.

The 120% rule is used too to the conductor and main breaker of the subpanel to determine the maximum allowed ratings for the back-fed PV breaker.  Consider an example below.

You have a meter-main combo panel which has 300-amp, the main breaker which has 300 and a breaker with 200-amp offering protection to a 200-amp subpanel. As explained above, the 200-amp panel will be shifted to the furthest point away from the main breaker. This will be done by exchanging positions on the breaker of the meter-main combo panel. The 200-amp subpanel is the only main lug in the subpanel.  Once the 120% rule is used as per the above-quoted code section, it would permit up to 40-amp from the back-fed PV breaker provided that the breaker is placed on the furthest position from the conductor.

There is no need to change the size of the feeder due to the fact that the generation of currents by the PV will counteract the utility current thus lowering the total current in the feeder and the meter-main conductor.

The Feeder Tap with the new panel board.

This is a second method whereby a connection to a PV system is by tapping a position of a feeder on the present meter-main combo panel. This should be at a precise position which is found almost to the remote load. There should be strong protection of the feeder running from the connection area to the remote panel. This protection is against overcurrent which may come from the utility or PV system. The code gives the options on how to deal with the problem, this is under section 705.12(B)(2)(1)(a) and (b). It is widely recommended to use, option (b) rather than option (a) because it is relatively difficult to substitute both the whole feeder to the remote position.

The simplest method is to increase a small lug on the panel board. This addition should be at a minimum of two positions at the junction between the PV output circuit and the breaker feeder. A function of a first breaker is to defend the remaining feeder and the remote panel while a second breaker functions to act as the PV inverter alternative current output breaker.

Consider the following example

One hundred and twenty-five-ampere breaker supplying to the one hundred and a twenty-five-ampere main lug sub panel in the two hundred ampere main-meter combo panel. The breaker is placed in the right location far away on the main-meter conductor. The load center will be placed next to the main-meter combo. The feeder will be channeled via the load center and the circuit from the breaker will pass via the new load center to the main lugs. The elongation of the channel from the feeder to the remote subpanel will be achieved through joining this circuit to the breaker with one hundred and twenty-five amperes in the load center.

The inverter for the PV is rated at fifteen amperes output, thus a twenty-ampere breaker can be put in the new load center to join the PV system output. As stated in section 690.9, the calculations here will be as follows. 15 amp x 1.25 = 18.75 amp thus the maximum allowed current would be to nearly 20 amps. If one hundred and twenty percent rule is applied a maximum of twenty-five back-fed PV systems can be allowed to be put. Under these conditions, overcurrent is prevented and thus there is no need to replace or upgrade. If you are using this panel, there is no problem if you add a new two hundred panel ampere panel board and you may use up to one hundred and fifteen amperes in a back-fed PV system. At this condition you will be implementing a one hundred and twenty percent rule thus feeder overloading will be avoided.

This rated breaker will be able to offer protection from a remote sub panel to the downstream feeder. Also, if the upstream feeder is rated the same as the downward stream then, the passing utility and PV currents would not be high to exceed the rated amount. Thus, the utility currents in the feeder will be lowered by PV currents coming back to the main-meter panel since they will cancel each other and hence reducing any current which is less than one hundred and twenty-five amperes.

You should bear into your mind that, if you are computing breaker values, then when you add breakers that have proper ratings, you are offering protection to various conductors against overload and short-circuits.

The Main-Lug-Only Service Panels having Six Main Breakers

Breaker positions that are not filled.

These panels are widely available all over the country and bring some problems when connecting a PV system. These are used only when meter conductors are joined to the main lugs. In most situations, the manufacturer’s instructions on the panel board provide that if you want to use your appliance as a piece of service equipment, then you should select one position to use it as the main breaker. Under this situation, remaining positions become load-side connections, if connected to the PV back-fed breaker then section 705.12(B) comes into effect. The simplest and unusual condition occurs if one of the six positions is not used. If you use such a position in a back-fed PV breaker then, this position will be a supply-side connection. You may use any ratings for the back-fed breaker, panel conductor or service provided that the panel board producer allows.

For example

A 300-amp service panel consists of a single empty breaker position. Both the panel and service panel are having ratings of 300 amps. Under this situation, a 300-amp back-fed breaker can be put in the empty position provided that, panel board manufacturer allows. A 300-amp breaker allows an inverter outputs rating to be 240-amps which is equal to 80% of the 300-amps. Note that most panels do not permit a breaker which is full conductor rating.

A factor behind this is that the total load on a panel conductor must be less than the conductor rating as per section 230 and 240 of the NEC handbook. It is limited to have a total rating of power productions to be greater the ratings of the service devices.  This note is per section 705.12(A).

The caution

Though it is not a code prerequisite, it is recommended that those back-fed PV breakers having ratings that are almost the same as the conductor ratings should be placed far away from the input of the main lug. The advantage of this act is to avoid addition of PV currents to utility currents. If the process is not avoided and thus occurs, accompanied by high PV production then these currents will overload the conductor. The PV currents will resist the utility currents in the conductor leading to the reduction of the conductor current.

Tap the feeder.

In circumstances where all breaker positions are full, fixing the feeder may be done through the installment of the new panel board close to the existing panelboard as explained before. When you have a feeder with a short distance, in the middle of the service panel and new panel, then you can increase the distance to permit a larger quantity of back-fed PV. The ratings for the newly installed panel board may equate with those of the existing original feeder breaker. This has one advantage that it can be a protective measure to the downward parts of the feeder.

The summary

The NEC does not recommend the usage of PV connections when installing a service panel. Thus it is very important to make a close examination of other requirements stipulated in the law that may help to install connection safely. All installers should be careful when dealing with these situations and how are they dealt with by the PV installers. Amendments of the NEC will address these allowances and limitations.

Protecting Your Motor By Installing Manual Starters And Switches

Some devices are termed as Electric manual starters and switches. They are very compacted and pleasingly very simple designed devices that are installed used to turn motors either on or off. Though they are very simple, still they can reverse the motor depending on the design of the motor. They offer protection against overloads, shorts, and phase failures in systems that do not consist of fuses. They are traditionally operated by a fixed rod or push button. They are in several options running from reversing and non-reversing to multi-speed choices. It is very easy to select the proper motor starter and switch versions to be used by your system

Systems Considerations

It should be known that manual starters are manufactured to be used in low horsepower motor systems. Of course, most small motors are designed to run on small horsepower.

They are designed to be raised and fitted directly onto or near the machine. They may be used in the form of stop-starts, this will not require to use excessive power cords and wires.

The selection of starters can be made depending on the type of device which is going to use the starter. You may ask yourself some questions such as, is the system a single-phase or three-phase? What is the maximum voltage it can handle? Is your system need 1 or 2 pole structure or 2 or 3 pole structure?

Another factor is the environment in which the starter is going to be operating. Some areas require starters to be dustproof or be oil and corrosion-resistant. If it is going in the dust environment, the starter should be coated with 12 enclosures that prevent the starter from dust, dirt, and dripping non-corrosive liquids, oil, and lubricants. A type 4 enclosure is coated to the starter that is going to be used in outdoor areas with high moisture contents and wind-driven rain.

Few designs of starters are enclosed in special enclosures.  For example, Type F fraction horsepower starters are enclosed in type 1 enclosures. Type 4 enclosures consist of zinc alloy.

Several designs have a special operator too

Thermal overload is one of the very important things to consider to secure a motor against overheating.  For example, the environmental temperature of a room having many electronics would be so hot that annoying tripping is possible.

To avoid these problems, most switches, for instance, the type M and T units, have melting alloy thermal structures. If the surrounding temperature attains a set level, the protective relay passes via a physical change from solid to liquid and cuts off the power in the motor. At large this minimizes the chance of motor damages.

These are just a few things to consider when selecting the right manual starter or switch for a certain system.

Fractional Horsepower Manual Starters

This type of manual starters offers overload security and switches thee power manually. They are mostly used in appliances with small motors such as in fans, industrial conveyors, and other small machine tools. They are manufactured either enclosed or open. They are too in non-reversing and two-speed versions to monitor small single-phase alternating current in motors with different high- and low-speed winding operation. Also, horsepower may reach up to 1hp alternating current. Overload prevention is by melting units having alloys. Pole configurations may be either single or double for alternating current.

Manual Starting Switches

Manual starting switches use two switches. One switch is used to start the motor for the clockwise movement while the other is used for the anticlockwise movement. They offer manual switching control of a single- or three-phase alternating current motors. Also, they are for reversing alternating currents motors if overload prevention is not important or given separately. It is very convenient to use them with the three-phase squirrel cage motors.

They are designed either enclosed or open, tightly packed and have a 600 V rating. They are proper choices for a wide range of industrial and commercial applications such as in small machine tools, air conditioners, fans, and ovens. They may be used on non-motor loads.

They are manufactured in different options such as reversing, non-reversing, and two-speed versions. For example, there some of them that have horsepower rated up to 20hp.

Integral Horsepower Manual Starters

These are designed to protect the system against overload hazards and turns on or off to monitor a small single-phase, many phase or direct control motors. There are several options to select from such as non-reversing and reversing. They are widely used in areas that have small hand tools, pumps, fans, and small conveyors. Horsepower may go up to 10 horsepower alternating current with three phases, five horsepower alternating current with single-phase and two horsepower with direct current.

They may be enclosed or opened.

Selections of manual starters and switches

As we have discussed before manual starters and switches are designed in many models. Due to this having a lot of product variables from systems to enclosure type, configurations and maximum voltage, choosing the right starter or switch will be a challenge thus you should be careful otherwise find assistance from certified individuals.

Electrical Power Equipment

Electrical panel components refer to the devices that are used in electrical power circuits to supply electric currents to electric appliances such as the air conditioner, Heaters, and ovens. According to the law in the United States, when making electrical wiring you should adhere to several codes. These are the National Electric Code (NEC) and the National Fire Protection Association (NFPA) code. These codes explain how to safely install your electric circuit.

For example, the NEC codes instruct that each electrical circuit should consist of safety switches or circuit breaker or fused disconnect and prevention systems against circuit overload. Overload protection is also important in the motor circuit. If these systems are placed in the circuit they offer protection against overheating that may lead to an outbreak of fire or explosions.

Meaning of a circuit Breaker

This is a manually operating power switch capable of discovering the presence of short circuit, overload or any other fault condition in the circuit. There are several types of circuit breakers the widely known and used being thermal magnetic. Short-circuits presence will be detected by the magnet while the overload is discovered by temperature changes. Any of the if discovered it cuts off the power.

The benefit of using this is that it does not get harmed or undergo self-destruction as it is the case of fuse disconnect. If you solve the problem that leads to tripping, then you may press on the button on the circuit breaker to allow the flow of electricity.

Meaning of a fused disconnect

A Fused Disconnect is the combination of a manually operated electrical power switch and a fuse. A fuse refers to the safety device which is made up of a thin metal wire which is placed in a sandpaper wrapper and melts if the passing electricity will exceed the rated allowed current thus leading to power shut down. This occurs if there are a short-circuit or overloads in a circuit and a fuse itself gets destroyed by melting.

There is a disadvantage of placing a fused disconnect in a circuit for security, compared to a circuit breaker, which is that fuse melts down making it not suitable for use again after correction of the error. itself breaking the circuit. After fixing the problem, you must replace a fuse with a new one.

Meaning of a Motor Starter.

It is a term used for any device or system of devices used to switch on and off and monitoring the motor. At least the motor starter should consist the some of the above-mentioned electric safety devices.  Also, devices such as contactor, soft Start and Variable Frequency Drive may be added to the safety control panel.

Disconnecting Means – a method of manually disconnecting power.

Circuit Overload Protection is an automated system in the circuit of shutting down the power if an overload situation occurs to avoid the circuit from getting hot and erupting the fire.

Motor Overload Protection is an automated system in the motor of shutting down the power if an overload situation occurs to avoid the motor from getting hot and erupting the fire.

Meaning of the full voltage non-reversing starter.

Abbreviated as FVNR this a motor control device having three phases and a single motor contactor. It is also known as An Across the Line (ATL) Starter. Turning on and off is done by opening and closing the contact current circuit.

When saying Full Voltage means the function of the contact is open and close the current circuit leading to full voltage.

Non-Reversing means the reversal of the motor is not possible simply by using a single motor contactor.

The meaning of the Full Voltage Reversing Starter.

Abbreviated as VFR starter this a motor control device having three phases and two motor contactors. In this model closing and opening are achieved by forwarding and reversing the contactor to monitor the direction of the motor instead of using a single contactor unlike in the above design.

Full Voltage here means the capacity of the contactor to easily open and close the motor power circuit.

Reversing here means the ability of the motor to reverse either using a forward or reverse motor contactors.

The meaning of a Soft Starter

This a motor control device having three phases and one solid-state power controller. In contrast to motor contactor, soft starter decreases or increases the electric current at the regular intervals turn open and close the motor circuit more smoothly which in turn reduces the possibility of occurrence of electrical surges and mechanical shock.

Soft Start means to increase the motor currents to open the motor smoothly

Soft Stop means to decrease the motor power close the motor smoothly

A Soft Starter is not cost-effective as compared to the motor contactor, though they have added advantages of minimizing electrical and mechanical shocks related to turning on and off the motor.

The meaning of a variable frequency drive (VFD).

This a motor control device having three phases and an advanced solid-state power controller. In contrast to working like the soft starter controller, the Variable Frequency Drive functions by permitting checking of the motor speed during the whole operating time of the motor.

A Variable Frequency Drive is the most expensive controller, though it offers the added advantages of motor speed control.

Understanding A Rely and How It Works

A relay is a component that is responsible for opening or closing a contact whenever it is energized. Normally you will find relays in power systems where they work to identify defective apparatus or lines or any malfunction. Besides they work to initiate the effective control action to resolve a problem or prevent further damages in the system.

How does a relay operate?

Whenever the voltage or current rises above the specified limit the relay contact moves from its position leading to action in the circuit breaker. This is movement is made depending on the information which comes from the measuring components and directed to the trip coil of the circuit breaker. In some of the systems, relays are used as switches for turning on and off the machines and equipment.

The types of relays

Despite the fact that a relay is nothing more than an opening or closing switch but depending on the application and the location where it should be used relay devices have different types and names. A relay can be applied in appliances, HVAC, Pool and Spa, security, Telecommunications, Energy management systems, appliance controls, timers, test equipment, motors, etc.

These are common types of relays that are used in different systems

  • The auxiliary relay: This is normally used in power system protection systems that are not capable of detecting any fault within the system. An auxiliary relay consists of a reclosing, lockout relays, and circuit breaker anti-pump relays.
  • The differential relay: This has multiple inputs and is designed specifically for protecting high power buses.
  • The computer relay: This is a type of a protective relay that digitizes the voltage and current signals then sends them to a microprocessor which is responsible for conditioning the digitized signal and implementing the logic operation.
  • The differential relay: This measures the entire current which is entering the device from all the sources using a paralleled current transformers network. Normally the operational current is set to zero for normal conditions, and when it rises too high values it indicates a fault. Differential relay is among the protective relays and is commonly used in transformer protection, bus protection, large motor protection, and generator protection.
  • The digital relay: This is a microprocessor system whereby the digital computer is responsible for making decisions.
  • The directional overcurrent relay: This is a type of an overcurrent relay that will function only when there is an overcurrent that is flowing in the tripping direction. The direction sensing is normally done depending on the voltage or the current signal that cannot be affected by the location of the fault.
  • The directional power relay: This is among the protective relay that functions for power flow within a given direction. This is used in systems where there are normal power flows head in a single direction such as the anti-motoring protections installed on turbine generators as well as the back feed protection that can be found on a parallel step down transformers.
  • The distance or impedance relay: This is the only type of relay that operates depending on the distance of the fault within the line. Its working principle depends upon the ratio of the system current or voltage.
  • The electromechanical relay: This is also a protective relay that uses magnetic, electrical as well as mechanical circuits to trigger the operating logic.
  • The Fourier optics relay lens: This consists of a lens system that is responsible for producing the same Fourier transform of an image. Two same relay lenses will create an image with no need for any phase curvature.
  • The frequency relay: This is a type of protective relay that is responsible for monitoring the electric power system’s frequency.
  • The generator differential relay: This is specifically designed aiming at protecting the electric power generators. It can be found in variations that include the allowances for managing split phase winding machines.
  • The instantaneous overcurrent relay: This is a type of overcurrent relay that functions without intentional delay as soon as it senses an overcurrent within the power frequency such as a current that is above the set value.
  • Lockout relay: This is controlled by protective relays that are responsible for opening the right circuit breakers or any other fault clearance equipment. This will always remain in a trip position until it is manually reset. This is normally found in protective zones that experience temporary faults that might cause equipment damage.
  • The loss of field relay: This is a protective type of relay that is used in tripping a synchronous generator in a situation where is a loss of the excitation system. When this occurs a generator will run just like an induction generator causing it to draw reactive power from the system. This might lead to severe voltage fall and might end up damaging the stator due to extreme heating.
  • The master control relay: It is commonly seen in programmable logic controllers to maintain the entire programs or particular rungs of the program. The master controller will override any timer condition. It does not matter whether it is a time on or time off, it will work to secure all program contacts and make sure they are in safe conditions.
  • The negative sequence overcurrent relay: This is a type of protective relay that identifies and functions over a negative overcurrent sequence. This normally used in detecting unbalanced faults as well as protecting synchronous and induction machines from rotor overheating.
  • The out of step relay: This is also a type of protective relay that detects if the synchronous generator has pulled out of the step. It operates on a frequency that is different from that of the system.
  • The overcurrent relay: Is also a protective type of relay that functions when it is fed with a current that is larger than its maximum pick up point.
  • The overload relay: This is a device that is designed to sense and interfere with any motor overload conditions. Sometimes they might be installed with magnetic, electronic, and thermal sensors.
  • The overvoltage relay: This is another type of protective relay that deals with overvoltage faults.
  • The phase comparison relay: This is among the protective relay types that are normally used in transmission lines which deal with comparing phase angles signals that originate from opposite ends of the line. They use dedicated communication media to do the comparison. The signals that are compared are normally corresponding sequence or phase currents.
  • The protective relay: This refers to a device that is capable of monitoring the condition of the electric power system and identify any faults or other abnormalities. This device is categorized under the protective relay type and can monitor voltage level, current flow or any other parameters. Whenever there is a fault or any abnormal event it triggers a trip signal that leads to the opening of a right circuit breaker or any other protective component.
  • The reclosing relay: This is an auxiliary relay that triggers the circuit breaker sending in a set of sequences aiming at fault clearing. The reclosing relays are normally used on overhead lines which experiences a lot of temporary faults.
  • The residual overcurrent relay: This is responsible for detecting residual current. Residual current is defined as the sum of three-phase currents that are running in a current transformer secondary circuit while being proportional to zero-sequence current running in the primary circuit at that value. 
  • The seal in the relay: This is an auxiliary relay type that is always energized via one of its contacts that go passes the initiating circuit until any other device de-energizes it.
  • The solid-state relay: This is a type of relay that uses logic electronics, analog, and magnetics in implementing the operating logic.
  • The sudden pressure relay: This is a protective relay that detects the internal pressure within the transformer and takes action to deal with abrupt changes in this pressure where these changes normally indicate a fault within the tank.
  • The synchro check relay: This is another type of protective relay that monitors the frequency and phase angle of the voltages over an open circuit breaker. Synchro check relays are applied in preventing circuit breakers from closing or reclosing whenever there is an excessive frequency or excessive difference.
  • The synchronizing relay: This is the type of relay that is responsible for monitoring voltage over the open circuit breaker in order to detect the frequency and phase relationship of the voltage sources on both sides of the breaker. They are commonly used on generator breakers to match the generator to the system frequency as well as the phase angle between the generator and the system before the breaker is being closed.
  • The time overcurrent relay (TOC): This is an overcurrent relay that consists of selectable, time delay and intentional features. The time delay is ideal for making the relay device function slowly as compared to the downstream relays or fuses while faster than the upstream relays or the transformer fuses. The fuse and relay curves are normally displayed upon time-current curves.
  • The time delay relay: This is the type of relay that functions by responding with intentional time delay. The following are the applications of time delay relays:
  • When applied to control circuits, they work to create a time delay in the form of relay whenever power is opened or closed to the relay actuator.
  • When used in power systems their response time normally depends on the size of the value measured. In case the value measured is a large multiple of the pickup value, then the relay gets into action or trips after a delay. When there are normaler multiples pickup, the relay will take a longer time to trip.
  • The transformer differential relay: This is a type of relay which is specifically designed for protecting transformers. The transformer differential relay deals with the current transformer turns ratio error as well as inrush and excitation current.
  • The under-frequency relay: This is a type of protection device that reduces loads in an area that is insufficient in generation. When there is a lower generation while there are higher demand loads lead to a lower frequency and a frequency threshold that can be used by the relay to trigger load shedding to balance demand and generation.
  • The voltage relay: This is a type of protective relay that deals with low or loss voltage.
  • The voltage regulating relay: This is a voltage monitoring relay senses (RMS), issues and voltage level to components such as the load tap changers, which then configure the tap location to reset the voltage to its desired level.