Connecting a reversing magnetic starter. Connection diagrams for three-phase electric motors. Starting diagram for a three-phase motor with reversal.

This circuit is quite often used to connect a three-phase electric motor where operational control of the direction of rotation of the motor shaft is necessary - for example, in garage doors, pumps, various loaders, crane beams, etc.

Reversing the motor is realized by changing the phasing of its supply voltage. For example, if the order of connecting the phases to the terminals of a three-phase electric motor is conventionally taken as L1, L2, L3, then the direction of shaft rotation will be certain, opposite than when connected, say, with phasing L3, L2, L1.

A special feature of the reversible connection scheme is the use of two magnetic starters. Moreover, their main power contacts are connected to each other in such a way that when the coil of one of the starters is triggered, the phasing of the engine supply voltage will differ from the phasing when the coil of the other is triggered.

The circuit uses two magnetic starters. When the first starter KM1 is triggered, its power contacts are attracted (circled in green dotted line) and voltage with phasing L1, L2, L3 is supplied to the motor windings. When the second starter - KM2 - is triggered, the voltage to the engine will go through its power contacts KM2 (circled in red dotted line) and will already have phasing L3, L2, L1.

As you can see, here the magnetic starters are connected according to the standard circuit. Unless, in the circuit of each coil, a normally closed block contact of another starter is connected in series. This measure will prevent a short circuit in the event of mistakenly pressing both Start buttons at the same time.

Reversing magnetic starters in a single-phase network. Reversible electric motor connection diagram.

To start the electric motor in direct And reverse direction, a reversible control circuit is used on the magnetic starter.

At the conclusion of this article, watch a video demonstrating the detailed operation of the engine reverse starting circuit.

First, let's look at the reverse connection diagram with a 220V magnetic starter coil, and then the operation of the circuit.

Phases A, B and C of the supply voltage are supplied to the terminals of the asynchronous motor through:

— 3-pole, which protects the entire circuit and allows you to turn off the supply voltage;

— alternately through three pairs of power contacts of magnetic starters KM1 And KM2;

- thermal relay R, which serves to protect against overloads.

In order to change the direction of rotation of a three-phase electric motor, it is necessary to swap the connection of any two phases!

To do this, the motor winding circuit includes power contacts from two starters, which are connected alternately, changing the phase sequence. In our scheme, when rotating forward the sequence of phases is as follows - A, B, C. During rotation back- C, B, A. I.e. the alternation of phases A and C is reversed.

The coils of magnetic starters are connected on one side to the neutral working conductor N through a normally closed contact of a thermal relay R, on the other, through the push-button post to the phase WITH.

The push-button post consists of 3 buttons:

1) normally open button FORWARD;

2) normally open button BACK ;

3) normally closed button STOP .

To button FORWARD Normally open auxiliary contact of the starter is connected in parallel KM1, and accordingly, to the button BACK— normally open auxiliary contact of the starter KM2.

Also in the power supply circuit of the starter winding KM1 Normally closed contact of the starter is switched on KM2, and into the starter winding circuit KM2, the normally closed contact of the starter is turned on KM1. This is designed to be a lock to prevent the engine from running backwards when it is turning forwards and vice versa. Those. The engine can only be started in either direction from the stop position.

Circuit operation

Move the three-pole lever to the on position , its contacts close, the circuit is ready for operation.

Running forward

Press the button FORWARD . Magnetic starter winding power circuit KM1 closes, the coil armature retracts, closes the power contacts KM1 and auxiliary normally open contact KM1, which bypasses the button FORWARD .

Simultaneously auxiliary normally closed contact KM1 opens the magnetic starter control circuit KM2, thereby blocking the possibility of starting the engine reverse.

Three supply phases in the sequence A, B, C are supplied to the motor windings and it begins to rotate forward.

Release the button FORWARD , it returns to its original normally open state. Nowpower supply to the starter winding KM1 supplied via closed auxiliary contact KM1. The engine is running and rotating forward.

Stopping the engine from FORWARD position

To stop the engine or start it in the other direction, you must first press the button STOP .The control circuit power is interrupted. Magnetic starter armature KM1 under the action of a spring it returns to its original state. The power contacts open, cutting off the supply voltage from the electric motor. The engine stops.

At the same time, the auxiliary contact opens KM1 in the power supply circuit of the starter winding KM1 and the auxiliary contact closes KM1 in the starter power circuit KM2.

Release the button STOP . It returns to its original, normally closed position. But since the auxiliary contact KM1 is open, power is not supplied to the KM1 starter winding, the engine remains turned off and the circuit is ready for the next start.

Engine reverse

To start the engine in reverse direction, press the button BACK.

Power is supplied to the starter winding KM2. It is triggered by closing the power contacts KM2 in the motor power supply circuit, and an auxiliary contact KM2, which bypasses the button BACK. At the same time, another auxiliary contact KM2 breaks the starter power supply circuit KM1.

Three phases are supplied to the motor windings in the order C, B, A, and it begins to rotate in the other direction.

Release the button BACK. It returns to its original position, but power is supplied to the starter winding KM2 continues to flow through the closed auxiliary contact KM2. The motor continues to rotate in the reverse direction.

Stopping the engine from the REVERSE position

To stop, press the button again STOP. Starter winding power circuit KM2 opens. The anchor returns to its original position, opening the power contacts KM2. The engine stops. At the same time, auxiliary contacts KM2 return to their original state.

Release the button STOP, the circuit is ready for the next start.

Overload protection

Thermal relay operation R and purpose of the fuse F.U. I discussed it in detail in the article, so I’m omitting the description in this article. For starters with windings designed for 380V, The connection diagram will be as follows.

Reverse (aviation)

The engine reverser flaps are activated and redirect the jet stream against the movement of the aircraft.

Reverse- a device for directing part of the air or jet stream against the direction of movement of the aircraft and thus creating reverse thrust. In addition, reverse is the applied mode of operation of an aircraft engine that uses a reversing device.

Reverse is used mainly during the run, after landing, or for emergency braking during an aborted takeoff. Less often - when taxiing, to move the aircraft in reverse without the help of a towing vehicle. A small number of aircraft allow the reverse to be activated in mid-air. Reverse is most widely used in commercial and transport aviation. A characteristic noise can often be heard when an airplane runs along the runway after landing.

Reverse is used in conjunction with the main (wheel) braking system of the aircraft. Its use makes it possible to reduce the load on the main braking system of the aircraft and shorten the braking distance, especially when the coefficient of adhesion between the wheels and the runway is low, as well as at the beginning of the flight, when the residual lifting force of the wing reduces the weight on the wheels, reducing the effectiveness of the brakes. The contribution of reverse thrust to the total braking force can vary greatly among different aircraft models.

Jet engine reverse

Using reverse to slow down an aircraft when landing.

Reverse is realized by deflecting part or all of the jet emanating from the engine using various shutters. In different engines, the reversing device is implemented in different ways. Special shutters can block the jet created only by the outer circuit of a turbojet engine (for example, on the A320), or the jet of both circuits (for example, on the Tu-154M).

Depending on the design features of the aircraft, both all engines and part of them can be equipped with reverse. For example, on the three-engine Tu-154, only the outer engines are equipped with a reversing device.

Restrictions

The disadvantages of the reversing system include the troubles associated with its use at low speeds (approximately<140 км/ч). Реверсивная струя может поднимать в воздух с поверхности взлётно-посадочной полосы мусор (например, мелкие камни), который, при пробеге самолёта по ВПП на относительно небольшой скорости, может попасть в воздухозаборник двигателя и стать причиной его повреждения . При высокой скорости движения самолёта поднятый мусор помех не создает, поскольку не успевает подняться до высоты воздухозаборника к моменту его приближения.

Reverse engine with propeller

Turning the propeller blades.

Reverse in propeller-driven aircraft is realized by rotating the propeller blades (the angle of attack of the blades changes from positive to negative) while maintaining the same direction of rotation. Thus, the propeller begins to create reverse thrust. This type of reverse device can be used both on piston engine aircraft and on turboprop aircraft, incl. and single-engine. Reverse is often provided on seaplanes and amphibians, because provides significant convenience when taxiing on the water.

Story

The first use of thrust reverser on propeller-driven aircraft can be dated back to the 1930s. Thus, passenger aircraft Boeing 247 and Douglas DC-2 were equipped with reverse.

Airplanes without reverse gear

A number of aircraft do not require reverse. For example, due to the peculiarities of the wing mechanization and the extremely effective air brakes in the tail, the BAe 146-200 does not need to engage reverse when landing. Accordingly, all four engines do not operate in reverse mode. For the same reason, the Yak-42 aircraft does not need a reversing device.

Using reverse in the air

Some aircraft (both propeller-propelled and jet, military and civil) allow the possibility of turning on reverse thrust in the air, while its use depends on the specific type of aircraft. In some cases, the reverse is activated immediately before touching the stripe; in other cases - on a descent, which allows you to reduce the vertical speed by braking (when approaching on a steep glide path) or to avoid exceeding permissible speeds during a dive (the latter applies to military aircraft); to perform combat maneuvers; for a quick emergency descent.

Thus, in the ATR 72 turboprop airliner, the reverse can be used in flight (when the pilot removes the safety seal); the Trident turbojet also allows airborne reverse for rapid descent at a vertical speed of up to 3 km/min (although this feature has rarely been used in practice); For the same purpose, the reverse of the two internal engines of the supersonic Concorde airliner could be turned on (only at subsonic speed and at an altitude below 10 km). The C-17A military transport aircraft also allows all four engines to be reversed mid-air for rapid descent (up to 4,600 m/min). The Saab 37 Wiggen fighter also had the ability to reverse in flight to reduce the landing distance. The Pilatus PC-6 single-engine turboprop aircraft can also use mid-air reverse when approaching short landing areas on a steep glide path.

For an example of using reverse thrust in the air (immediately before touching the runway), you can give an excerpt from the flight manual for the Yak-40 aircraft:

at an altitude of 6–4 m, reduce the operating side engines to low throttle and begin leveling the aircraft by giving the command: Reverse.

see also

Notes

Links

• (English) Checking the operation of Learjet 60 reverse devices.
• (Russian) “Reverse educational program.” Photos of various models of reversing devices.
• (English) Landing IL-86 on a wet runway. Clouds of moisture well illustrate the operation of the reverse. Panoramic view.
• (English) Boeing 747 landing on a wet runway. Clouds of moisture well illustrate the operation of the reverse with the overlapping of the external contour. View from an airplane.
• (English) Boeing 737 landing. Illustration of reverse operation with both contours overlapping. View from an airplane.
• (English) Coming to a complete stop with the McDonnell Douglas C-17 in reverse caused debris to enter the engine and damage it.
• (English)
• (English) Illustration of how reverse works while taxiing. The plane is moving backwards.

Content:

A reversing starter is often found in equipment that ensures the operation of mechanisms and units that have the functional purpose of changing the rotation of the electric motor shaft. The connection diagram for a magnetic starter with reversible starting of an electric motor is always the subject of study by amateur and professional electricians to create their own designs.

In industry, there are two types of magnetic starters: for direct starting of an asynchronous electric motor, and also for reverse starting of an electric motor.

Irreversible motor connection

To better understand the reverse start of an electric motor, experts suggest considering how a non-reversible circuit for switching on an electric motor works. In a specific example, a starter with a 220 volt control coil is considered. The electric motor is connected to the circuit according to the following chain:

• automatic three-phase switch;
• starter power terminals (KM);
• thermal relay (TR).

The starter control coil (CM) on one side is connected to the working zero, and the other side, through a chain of “Start” and “Stop” control buttons, is connected to the circuit phase.

The control station (CM) has two buttons: “Start” and “Stop”:

• the “Start” button has normally open contacts;
• The “Stop” button has normally closed contacts.

The normally open contact of the control coil is connected in parallel with the start button. The thermal relay in this circuit plays a protective function against overload for the electric motor and is included in the supply phase break. A normally closed contact (TR) is included in the control coil (CM) circuit.

After turning on the automatic three-phase switch, voltage is supplied to the power contacts of the starter and to the control circuit of the coil - the circuit is brought into working condition.

Irreversible start

To start the electric motor, the operator needs to press the “Start” button, then voltage is supplied to the control circuit of the coil, the circuit is closed and triggered, retracting the armature while simultaneously closing the shunt contact of the control coil. The power contacts of the electric motor receive power and it begins to rotate.

When the operator releases the "Start" button, the winding (CM) receives power from its auxiliary contact, the engine runs.

Stop

To stop the non-reversible motor, the operator must press the “Stop” button, in this case the power supply to the control coil (CM) is interrupted, the shunt contact opens, the coil armature returns to its initial position, thereby opening the power contacts. The electric motor loses voltage and stops.

When the “Stop” button is released, the contact of the control winding remains open, awaiting the next start of the electrical circuit.

How does engine protection occur during irreversible starting?

Protection of the electric motor is realized using bimetallic contacts (TR), they bend as the current increases, and the release acts on the contact in the starting winding, stopping the supply of electrical energy. All contacts of the starter (KM) return to their initial position, and the engine stops. Below is a schematic diagram of a connected electric motor with protection.

The circuit for protecting the operation of an electric motor provides additional protection for the control of starting and stopping the mechanism; this is the inclusion of a fuse in the circuit, which reacts to the interturn closure of the starter control coil (CM).

Magnetic starter device for reverse starting

A reversible magnetic starter has a functional purpose - starting an electric motor, as well as other mechanisms that have a functional purpose of working in forward and reverse directions with a change in the rotation of the motor shaft. The starter performs the switching function with power contacts and supplying voltage to the motor.

Unlike contactors, a starter is used as protection for frequent starts and stops of mechanisms and devices. PML brand starters are widely used in three-phase motor reverse circuits to implement remote starting in pumping stations, in tower cranes and ventilation systems, and in other mechanisms.

The magnetic starter has the following functional components in its design:

• electromagnetic part with a coil and a moving armature, a normally open magnetic circuit;
• main power contacts, the purpose of which is to connect and disconnect the electric motor phases when starting and stopping. Reversible magnetic starters in their design can have contacts in the upper part of the structure and on the side of the armature winding (AM);
• block contacts are functionally designed for switching the control circuit;
• The starter transitions to the initial position using a return mechanism, this is a spring that the armature of the control coil (CM) returns to the initial position, opening all contacts.

How is the reversing starter connected?

The connection diagram for a reversible magnetic starter is necessary for operating an electric motor in the forward as well as in the reverse direction. Connecting this type of starting device is not difficult for a specialist. Very often in industry, reverse connection is used to operate various types of machine equipment (drilling machine, lathe, etc.). The reversible scheme is implemented in the operation of elevators for non-domestic purposes.

Reversing starters have a difference in connection; this is an additional control circuit, as well as a difference in the connection of the power section. The circuit implements short circuit protection; these are contacts KM1.2 and KM2.2, which have a normally closed form and are located on the starters KM1 and KM2. The reversible circuit shown in the photo has a color difference between the power and control circuits:

How does it turn on?

The reversing circuit of an asynchronous motor can be figuratively divided into switching stages: we move the switch (QF1) to the operating position, in this case all reversing magnetic starters on the power contacts receive voltages KM1 and KM2 and remain in that position.

One phase is involved in the control circuit of the starter windings, its passage:

• circuit breaker (SF1) - “Stop” button (SB1) - contact group No. 3 (function with buttons (SB2) and (SB3);
• contact 1ZNO in starters KM1 and KM2 becomes standby - it has a standby value;
• The reversing starter is ready for operation.

How does the switch happen?

The electric motor reverse circuit provides for the following manipulations in the starter: when the operator presses the SB2 button, it provides power to control the starter coil (KM1), then the normally open contacts are activated and the normally closed contacts in the KM1 configuration are opened, the coil provides “recharge”, and power is supplied through the power contacts enters the motor, it begins to rotate.

If there is a working need to reverse the electric motor, the operator needs to change the application of power contacts (phases), this is implemented using KM2. Important! Whenever the motor is connected for reverse rotation, it must stop; this is achieved by turning off the KM1 winding of phase No. 1 in the control, the contactors of the starter occupy the initial position, the electric motor is de-energized.

The operator, by pressing the SB3 button, supplies power to the control of the KM2 winding, and it changes the activation of the power contacts “phase No. 2” and “phase No. 3” for connecting a three-phase electric motor. It starts rotating in the other direction until the winding control contacts open.

Protection of motor reverse operation

Always, before changing the order of connecting a 3-phase motor, changing the order of phases on the windings of the electric motor, it is necessary to stop it. This is implemented in the switching circuit by normally closed contacts, which “safeguard” the operator’s work and prevent phase-to-phase short circuits in the electric motor when its connection is reversed. In the considered connection diagram for the reversing starter, it can be seen that only one starter can operate.

Every day there is work to connect direct and reverse rotation electric motors; the circuit diagram for switching on the starters is not difficult for qualified electricians. It must always be remembered that the function of stopping the engine must be implemented before it rotates back.

Today I will tell you about electric motor reverse.

In this article you will get acquainted with the electric motor reverse circuit and also learn how it works. And at the end, I made a special video for you, where I will show you the principle of operation of the electric motor reverse circuit on a special stand.

During the operation of a three-phase motor, moments arise when it is necessary to change the rotation of the electric motor shaft. To implement our plan, we connect the electric motor using a reverse circuit.

What do we need for this?

• Input power supply circuit breaker - in this example I used an AP-50 brand circuit breaker with a rated current of 4A
• Contactors or 2 pieces
• Push-button station with 3 buttons (red - “stop”, black - “forward”, “back”)
• Asynchronous electric motor

In my example (video) there is no thermal relay and the electric motor itself, because This stand was intended for training college students in assembling an electric motor reverse circuit without a power section.

Before moving on to reversing the electric motor, I recommend reading and thoroughly studying the following articles:

• (device, design, principle of operation using the example of PML-1100)
• non-reversible type

Now let's move on to the reverse. To change the rotation of the shaft (direction) of the electric motor, it is necessary to change the supply voltage.

How to do it?

Electric motor reverse circuit

I would like to immediately note that you should pay attention to the level of supply voltage of the electric motor (380V or 220V) and the voltage of the contactor coils (380V and 220V).

Below, see 2 more electric motor reverse circuits with different rated voltages.

In my example, the voltage level of the power circuit is 220 (V), so I use contactors with coils corresponding to 220 (V).

We use contactors KM1 and KM2 to organize the reverse of the electric motor. When the KM1 contactor is triggered, the phasing of the supply voltage will differ from the phasing when the KM2 contactor is triggered.

The coils of contactors KM1 and KM2 are controlled by the “stop”, “forward” and “backward” buttons.

Let's look at the operating principle of an electric motor reverse circuit.

Operating principle of the reverse circuit

When you press the “forward” button, the contactor coil KM1 receives power through the circuit: phase C - NC. contact of the "stop" button - n.c. contact KM2.2 of contactor KM2 - n.o. contact of the pressed “forward” button - contactor coil KM1 - phase B.

Contactor KM1 pulls up and closes its power contacts KM1.1. The engine begins to rotate in the forward direction.

There is no need to hold the “forward” button, because The coil of the contactor KM1 is set to “self-retaining” through its own contact KM1.3.

But. — normally open contact, n.c. - normally closed contact

To stop the electric motor, use the “stop” button. With the contacts of this button we interrupt the power supply to the coil (“self-catching”) of the KM1 contactor. The KM1 coil loses power and the KM1 contactor disappears, disconnecting the electric motor from the network.

When you press the “back” button, the coil of the KM2 contactor receives power through the circuit: phase C - NC. contact of the "stop" button - n.c. contact KM1.2 of contactor KM1 - n.o. contact of the pressed “back” button - contactor coil KM2 - phase B.

Contactor KM2 pulls up and closes its power contacts KM2.1. The engine begins to rotate in the opposite direction.

There is no need to hold the "back" button, because... the contactor coil KM2 is set to “self-retaining” through its own contact KM2.3.

In this circuit, the buttons are blocked from being pressed at the same time, otherwise it will occur in the power circuit, which will lead to damage to the electrical equipment. Blocking is performed by sequentially switching on the NC. contact (block contact) of the corresponding contactor.

The power circuit of the electric motor reverse circuit is equipped with a protective switching input circuit breaker AP-50 with a rated current of 4(A). It is also advisable to protect the control circuits by installing circuit breakers or fuses on phase B and C.

In the example (video) there is no protection for control circuits.

There are factory prefabricated contactors for electric motor reverse circuits with mechanical interlocking in the form of a toggle lever that blocks the simultaneous activation of the contactors.

In the comments they regularly write that this article does not fully cover the assembly of the reverse circuit. I am correcting myself and presenting to your attention step-by-step instructions for (follow the link). After reading this instruction, you will assemble the electric motor reverse circuit yourself.

P.S. For a more visual “live” example of electric motor reverse, I have prepared a video clip for you. Do not judge strictly. This is my first video created on the site. In the future I will try to add video lessons for each article.