By admin Articles circuit breakers and control devices electricity December 29, 2021

Electrical Power and Control Circuits

Electrical Power and Control Circuits are considered one of the best means of protecting loads. like electric motors, or any other load.

The power circuit is designed to feed the load to be operated in the appropriate manner directly from the source of supply; As for the function of the control circuit, it works to operate and disconnect the current passing into the contactor file or any other file such as the timer file.

Follow this article with us to know the difference between the control circuit and the forces, and the way to connect them.

What is the function of a circle of forces?

The main function of the power circuit is to work on delivering the electric current from the main supply source to the load to be operated through several tools and protections, Whether the load is inductive like motors or ohmic like heater.

The basic components of a power circuit

Electrical power circuits contain several devices, namely:

High endurance fuse for load current.
3phase magnetic thermal breaker.
The main points of the Overload .
The main points of the contactor .

Electrical Power and Control Circuits

Steps to connect the power circuit

Connect the power supply to the thermal magnetic circuit breaker or the fuse.
Connect the breaker output points with the contactor input points.
Connect the output points of the contactor with the main overload input points.
Finally, the overload output points are connected in series with the terminals of the electric motor.

What is the control circuit?

It is the circuit that controls the connection and disconnection of the electric current to the contactor coil, or any other file.

The circuit contains several tools to control the connection and disconnection of the electric current to the contactor coil, Like the point of contact of the overload, and the fuse, electric circuit breaker, contactor contact points, on and off switches, electric buoys, And the keys to the end of the journey…etc.

Electrical Power and Control Circuits

The basic components of the control circuit

Electrical control circuits usually contain several protection and control devices, namely:

Fuse.
1phase single face type magnetic thermocouple cutter.
Auxiliary points (closed and open) for the overload.
Auxiliary points (closed and open) of the contactor as needed for the control circuit.
On and off switches.
contactor files, The coil voltage must be proportional to the source voltage.
timer, overvoltage protection, Or heart or cut in one of the three Vases.
Signal bulbs.

Electrical Power and Control Circuits

Steps to connect the control circuit

Electrical Power and Control Circuits

Most control circuits have switches and contactor coils to control them.

Connecting the current source to the fuse in order to protect against any short current, Or an increase in the electric current may cause damage to the coils and protection devices.
The other end of the fuse is connected in series with the closed overload contact point in order to disconnect the current from the control circuit in the event of a fault.
Connect the power switch in series with the contactor coil.
Connect the auxiliary point of the contactor, To permanently operate the circuit when the power key is pressed.
Connecting the two ends of the contactor coil to the electricity to control the connection or disconnection of the main points from the electric motor.

Electrical Power and Control Circuits

The difference between a power circuit and a control circuit

circle of forces	control circuit
Designed to withstand high load current	Designed to play low current coils
You need contactors, overloads, and a 3-phase circuit breaker if the source of electricity is 3-phase.	You need auxiliary points, a 1-phase circuit breaker, and timers.

A table showing the difference between a power circuit and a control circuit

Conclusion

The control circuit is the circuit that operates and disconnects the power circuit by switches or timers of all kinds, sensors and electric floats.

Electrical Power and Control Circuits

What is a contactor and how does it work?

Electrical Power and Control Circuits

What is a contactor and how does it work? It is considered The contactor is one of the components of the electrical control system, which is commonly used in power and control circuits , as it is used to connect and disconnect the electric current about the load based on the control current fed to its coil, What is a contactor, how does it work, and what are its types.

What is a contactor?

The contactor is known as: contactor) as an electromagnetic switch that connects and disconnects circuits of power by feeding it a control current to its coil. Auxiliary points can be installed on it to use it in many other control functions such as disconnecting and disconnecting from another control device.

The contactor is available in the market with various brands at different prices, It comes in several shapes, types and sizes according to its ability and the nature of use.

The shape and symbol of the contactor

Contactor installation

The contactor has three main parts as follows:

iron heart It contains a fixed part in the shape of the letter E on which the electric coil is placed and a moving part that is attracted to the bottom when the coil is fed with electric current. The moment the current is disconnected from the coil, the moving part returns to the top by the action of the spring.

The contactor coil comes with different voltages (24V, 48V, 110V, 220V, 380V), The voltage of the coil is written on the data sheet affixed to the side of the contactor.

Contactor’s main points: Also known as (Main contacts), The main current input points (load current) are denoted by the symbols (L1, L2, L3), and the numbers 1,2,3 are usually written next to the symbols. While the main output points of the contactor are denoted by the symbols (T1, T2, T3) and usually written next to the symbols are the numbers 4,5,6.

Auxiliary contactor points: (in English: auxiliary contacts), These points are used in control circuits, Independent auxiliary points can also be installed with the contactor.

Auxiliary points are open points of contact. normally open) in the normal case and abbreviated by the letters NO and numbered by the numbers (13,14), or normally open contacts, It is abbreviated by the letters NC and numbered by the numbers (12,11).

Electrical Power and Control Circuits

How does the contactor work?

When feeding the contactor coil with an appropriate voltage, It will work to attract the moving iron core part down by the action of the spring, causing the main points and open contacts to connect and the closed contacts to separate from each other, This allows a large electrical current to be passed through its main points to the electrical load.

When the control current is disconnected from the contactor coil, The moving iron part returns to its normal position, that is, it rises up due to the force of the spring. which causes the main contacts (NO) to return to normal, Returns closed auxiliary contacts to the junction position and vice versa with open contacts.

Electrical Power and Control Circuits

What are the types of contactors?

There are several types of contactors, each type suitable for carrying the following:

AC1 type contactor: This type is suitable for resistance loads such as heaters and lighting units. and small inductive loads such as motors of small power, When choosing this type, the contactor must be able to withstand at least 1.25 of the load current. One of its advantages is that it is the cheapest type of contactor.

AC3 type contactor: It is the second type of contactor and it is specially made to work with high inductive loads such as large “three phase induction motors”. The Kontakor is designed to withstand ten times the total motor current. But it is more expensive than AC1.

AC4 type contactor: The last type is similar to the AC3 type in the operation of large motors, but it is characterized by the fact that it bears circuits in the opposite direction of the movement of the motor, 3 phase. In addition to its ability to withstand higher currents than AC3, This type can be used for circuits that are switched on and off several times within a short period. This is the most expensive type of all contactors.

How to choose the right contactor?

There are several factors that determine the process of selecting the appropriate contactor, including:

The operating voltage of the contactor.
Current type (AC,DC).
The number of major contact points.
The type and nature of pregnancy.
Maximum operating voltage and sudden voltage.
Less running current.
The number of times the contactor is turned on and off.

Explain the work of the contactor

Explain the work of the contactor, the contactor An important component in electrical control circuits, Because of its importance and its great role in the separation and operation of the electrical load such as the electric motor based on a control signal from the circuit.

The contactor is widely used in power and control circuits. And main and subsidiary electrical distribution panels that are located in: factories, hospitals, residential towers, And other different places that need to control a load.

contactor

Definition of contactor

The contactor is known as: Contactor) as a mechanical switch between the electrical power circuit and the control circuit to disconnect and connect the two circuits based on the presence or absence of an electrical signal.

He is responsible for connecting and disconnecting the electrical load according to the approved and based on control mechanism. It comes in different amperage capacities that vary according to the load voltage and the source.

Contactor Configuration

The contactor consists of the following electrical and mechanical:

a file.
spring.
Iron heart.
portfolio.
Movable contacts.
fixed contacts.

Contactor Configuration

It also consists of the external shape on the main points of entry and exit, and my point for feeding coil A1,A2, and an open auxiliary point, In some of its types, there is a closed point next to the open point.

The external shape of the contactor

Explain the work of the contactor

When an electric current is passed to the contactor coil based on a control signal from a circuit, It will change its contact points so that the closed points become NC in an open state, The open points are NO in a closed state.

When the control current is disconnected from its coil, Both: open points, And closed back to normal.

The control circuit can be based on the electric buoy or motion sensor, or a photocell circuit, or by pressing the on and off switch, Or when the first generator is disconnected and the second generator starts automatically, Or the control circuit by a timer.

There are a lot of control circuits that you can design and implement, In order to control the operation and separation of the contactor with ease.

How to choose the right contactor?

There are three factors to consider when choosing a contactor, They are:

The intensity of the current or the capacity of the load it will operate on.
The coil voltage must be compatible with the voltage of the control circuit.
The number of open and closed auxiliary contacts.

Connecting the main contactor electrodes

The power source and the load can be connected with the input and output terminals of the contactor in more than one way, But the main principle is based on everyone.

Overload delivery method

Overload connection method, The method of connecting the overload is one of the most important foundations that you must know for its direct relationship to the protection of electrical loads such as electric motors.

Where the method of overloading overlaps in electrical and industrial control systems to protect a load, There are several ways to connect the overload contact points to the control circuits, which are series, parallel, or both.

Follow this article with us to learn how to connect the overloads in series and parallel in order to protect the loads of electrical devices.

Overload function

Working to protect the electrical loads from suddenly increasing the electric current from the normal value, The result of cutting one of the vases and other malfunctions.

How to connect the overload to the power circuits

The main purpose of the main points of the overload in the circle of forces, It is the main current to the electric motor, due to the increase in loading.

Executive Connection to the Department of Power

As can be seen in the circuit diagram, The method of connecting the overload to the power circuit is constant, regardless of the number of electric motors. Except in some other circles, Like a power circuit to drive a left or right motor, Or a circle of star-delta powers.

Electrical Power and Control Circuits

Ways to connect overload contact points

The methods of connecting the overload contact points to the electrical control circuits are among the most important connections that protect the electric motors by disconnecting the current from the contactor coil or relay.

The method of connecting the overloads in series

This method is one of the best ways to protect the presence of more electric motors. Because it protects all motors from voltage drop, or who has lost one of the major prizes, And other malfunctions.

Where all the auxiliary contact points of the overload are connected in series, In the event of a failure in an electric motor, its overload disconnects the main contacts, and at the same time, the contact point disconnects the current from the contactor coil. Thus, the electric current will be disconnected from the rest of the motors as a result of separating the overload contact point connected in series with all other contact points.

Electrical Power and Control Circuits

Steps to connect the overloads in a row

As shown in the diagram above, Connect the open and closed overload contact points, respectively, with the contactor coils, It acts as a master switch for the control circuit. In order to disconnect the power supply from the control circuit in the event of a fault.
As for the power circuit, The main overload is connected in series with the terminals of each electric motor as shown in the power circuit diagram.

Overload connection in parallel

Each overload is connected independently from the other to protect each engine separately without affecting the rest of the engines, Meaning that if something malfunctions in one of the electric motors, its overload only disconnects, The rest of the engines remain in working condition.

Electrical Power and Control Circuits

Steps to connect the overload in parallel

As shown in the diagram above, Each contact point of the overload is connected in series with its first actuator, As well as connecting the contact point of the other overload in series with its second motor, In order to protect each motor separately from the other.
As for the power circuit, Each main overload is connected in series with the terminals of each electric motor as shown in the power circuit diagram

The difference between series and parallel overloading

The series circuit separates the total current source from the entire control circuit in the event of a fault in the electric motors.
As for the parallel connection circuit, it separates the electric current from the motor in which the fault occurred only. Through the contact point connected in series with the contactor coil.
It is preferable to use the method of connecting the overload points to the control circuits in series in most cases, Because it works to protect all motors against any possible electrical failure.

We have shown you how to connect the overload to the power and control circuits.

Electrical Power and Control Circuits

Connecting contactor with overload for beginners

Overload delivery with contactor for beginners

Connecting contactor with overload for beginners, In this topic, we will show you how to deliver Contactor with Overload for beginners with a detailed step-by-step explanation and what are the most important details that we, as beginners, must pay attention to when connecting contactor with Overload for beginners.

Before getting into the details of connecting the contactor with the overload, let us first learn about the benefit of both the contactor and the overload, and what is the importance of connecting them together in the power and control circuits .

The benefit of the contactor

The contactor is used in power and control circuits as an electromechanical switch, that is, the connection and separation of its main and auxiliary contact points is controlled according to the mechanism of the control effort applied to the contactor coil, Accordingly, the electric load, such as the electric motor, is turned on or off.

Electrical Power and Control Circuits

Overload utility

It is an overload device in its work on thermal protection, The overload is used as an accessory with the contactor or as a disconnected device, both of which have the same function, which is to protect the electrical load from a significant rise in the current value. The overload also has open (NO) and closed (NC) contact points that are used in control circuits.

Electrical Power and Control Circuits

Instructions for connecting the contactor with the overload

Ensure that the overload current range is consistent with the load current.
The value of the overload current should be set to the load current in the ratio of 1.05.
If the overload is of the type combined with the contactor, make sure that they are the same brand in order to ensure that the overload is well fixed to the contactor’s main output points.

Electrical Power and Control Circuits

The stages of connecting the contactor with the overload

The first stage: Connecting the power circuit, which is the circuit that feeds the electrical load, The contactor points (L1, L2,L3) are connected to the electricity source 3 phase, While the overload points that are in the form of copper electrodes are connected to the contactor output (L1, L2, L3).

The second phase: Connecting the control circuit by connecting the control wires with the auxiliary points of the contactor open (13,14) and closed points (11,12), We also connect the control wires with the numbered overload points (95,96) respectively before the disconnect or stop switch.

Electrical Power and Control Circuits

The experience of connecting the contactor with the overload

After making the necessary connections as shown in the image above, The electric motor is started by pressing the green start switch. After the engine has returned to its normal speed, press the red stop (disconnect) switch, The engine does not start again except by pressing the start key.

Important Notes:

Make sure that the overload current is set to the load current plus 1.05.
Ensure the correct connection of the overload contacts and connect the open contactor contacts to the control circuit in parallel with the switch.
Ensure that the connecting wires are well connected to the Contacour and Overload connection points.

Electrical Power and Control Circuits

Electrical Power and Control Circuits

How to connect the timer with the contactor

How to connect the timer with the contactor, This method is used when we want to control the connection and disconnection of the electrical load such as The electric motor during a predetermined period of time by the timer (timer), In this topic, we will show you how to connect the timer with The contactor .

The parts used to connect the timer with the contactor

2 phase circuit breaker (1 phase circuit breaker can be installed).
Seal-cutter (can be dispensed with if you have one).
timer 24 hours, (The timer designed with minutes can be connected in the same way).
Contactor , (selected so that it withstands the load current by at least 1.25).
Electric motor (any other electric load can be connected).

Electrical Power and Control Circuits

Explanation of the timer and contactor

timer: It is also called the timer. Timer), It is responsible for operating any electrical load after a predetermined period of time, It also has 24-hour timers and can control the operation and disconnection of the load at several preset intervals over the course of 24 hours.

timer

Contactor: Its function in the circuit is to connect and disconnect its main contacts and help to start and stop the electrical load based on the condition of the timer contacts, That is, the timer controls the connection or disconnection of the current to the contactor coil during a certain period of time, As a result of changing the timer contacts, it will also cause the main and auxiliary contact points to be changed.

Electrical Power and Control Circuits

Steps to make the timer work with the contactor

Initially, the timer connection delay time should be calibrated in minutes if it is designed in a minute system, And calibrate the 24-hour timer over a period of time according to what you want on the basis that it works to change its contact points during specific periods throughout 24 hours.

Here are the steps for making the timer circuit with the contactor as follows:

When the circuit is connected to the mains, A voltage is applied to both ends of the timer (A1, A2) with a small current.
The timer counts down to the preset time.
When the timer expires it will change its contacts causing the contacts to be connected in series with the contactor coil.
The electric current is then passed to the contactor coil, allowing the state of the main and auxiliary contact points to be changed.

Electrical Power and Control Circuits

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Electrical Power and Control Circuits

Electrical Power and Control Circuits 1

Electrical Power and Control Circuits