AC and DC motor reverse: wiring diagrams

Reversible switching of DC motors

It is easiest to reverse a DC motor with a permanent magnet stator. It is enough to change the polarity of the power supply for the rotor to start rotating in the opposite direction.

It is more difficult to reverse a motor with electromagnetic excitation (serial, parallel). If you just change the polarity of the supply voltage, then the direction of rotation of the rotor will not change. To change the direction of rotation, it is enough to change the polarity only in the field winding or only on the rotor brushes.

For reversing high power motors, the polarity must be reversed at the armature. A break in the field winding while the motor is running can lead to a malfunction. the resulting EMF has an increased voltage that can damage the insulation of the windings. Which will lead to failure of the electric motor.

To reverse the direction of rotation of the rotor, bridge circuits are used on relays, contactors or transistors. In the latter case, you can also regulate the rotation speed.

The figure shows a circuit with transistors. As an illustration of operation, the transistors are replaced with switch contacts. Similarly, bridge circuits are performed not on bipolar, but on field-effect transistors.

The efficiency of such a circuit is much higher than that of transistors. Control is carried out by a microcontroller or simple logic circuits to prevent simultaneous signaling.

Changing the direction of rotation of the rotor of an induction motor

The most widespread in the industry received asynchronous motors, powered by a three-phase voltage of 380 volts. In order to reverse, it is enough to change any two phases.

A connection diagram based on two magnetic starters has become widespread. Actually for DC motors, it is similar, but two-pole contactors or starters. This circuit is called "reversing starter circuit" or "reversible starting circuit of an asynchronous three-phase electric motor".

When you turn on the KM1 starter with the "Start 1" button, there is a direct voltage supply to the windings and the "Start 2" button is blocked from accidental switching on, by opening the normally closed contacts KM-1. The engine rotates in one direction.

After turning off the KM1 starter with the "Stop" button or by completely removing the voltage, you can turn on the KM2 with the "Start 2" button. As a result, the L2 line is fed directly through the contacts, and L1 and L3 are swapped. The "Start 1" button is blocked, since the normally closed contacts of the KM2 starter are set in motion and open. The engine starts to rotate in the opposite direction.

The scheme is used everywhere to this day to connect a three-phase motor in a three-phase network. The simplicity of the circuit design and the availability of components are its significant advantages.

The most widespread are electronic control systems. Switching circuits, which are assembled on thyristors without starters. Although starters can be installed for remote on or off in this circuit.

They are more complicated, but also more reliable than devices on contactors. For control, a pulse-phase control system (SPPC), frequency control systems are used. These are multifunctional devices, with their help you can not only reverse the asynchronous electric motor, but also adjust the speed.

At home, it becomes necessary to connect a 380V to 220V motor with reverse. To do this, it is necessary to switch the star-delta windings. We considered the differences between these schemes in more detail in an article posted on the site earlier: https://samelectrik.ru/chto-takoe-zvezda-i-treugolnik-v-elektrodvigatele.html.

However, if it is assumed connection of a three-phase electric motor to a single-phase network, then a capacitor is used for this, which is connected according to the diagram below.

In this case, in order to reverse, it is enough to switch the network wire from B to terminal A, and disconnect the capacitor from A and connect to terminal B. It is convenient to do this using a 6-pin toggle switch. This is a typical connection of an asynchronous electric motor to a 220V network with a capacitor.

Wiring diagram of the collector motor with reverse

To reverse a collector motor, you need to know:

1. Not on every collector motor you can reverse it. If the rotation arrow is indicated on the body, then it cannot be used in reversing devices.
2. All high speed motors are designed to rotate in one direction. For example, an electric motor installed in grinders.
3. The engine, which has a low speed, rotation can be carried out in different directions. These motors are installed in power tools such as electric drills, screwdrivers, washing machines, etc.

The figure shows a diagram of a universal collector motor that can operate on both direct and alternating current.

To change the rotation of the rotor, it is enough to change the polarity of the voltage on the winding rotor or stator, as in DC motors, from which universal machines practically do not differ.

If you simply change the polarity of the supply voltage on the collector motor, the direction of rotation of the rotor will not change. This must be taken into account when connecting the electric motor to the network.

You should also know that in high-power motors, the armature winding is commutated. When switching the stator windings, a voltage occurs self-induction, which reaches values ​​that can damage the engine.

Amateur constructors use various engine types. Often they use a brush motor from an automatic washing machine. These are convenient motors that can be connected directly to a 220 volt network. They do not require additional capacitors, and the speed control can be easily done using a standard dimmer. Six or seven leads are brought out to the terminal block.

Depends on engine type:

• Two go to the collector brushes.
• A pair of wires comes from the tachometer to the block.
• The field windings can have two or three wires. The third is used to change the speed of rotation.

To reverse the motor from the washing machine, you must swap the leads of the field winding. If there is a third pin, then it is not used.

Arduino electric motor reverse circuit

In model construction or robotics, small DC brushed motors are often used, which are controlled by an Arduino programmable microcontroller.

If the rotation of the motor is supposed to be only in one direction, and the power of the electric motor is small, and supply voltage from 3.3 to 5 volts, then the circuit can be simplified and powered directly from the arduino, but so rarely done.

In models with remote control, where it is necessary to use the reverse of motors with a voltage of more than 5V, keys assembled in a bridge circuit are used. In this case, the connection diagram of the motor with reverse on the arduino will look similar to what is shown below. This inclusion is used most often.

In the bridge circuit, field-effect transistors or a special matching device - a driver, with the help of which powerful motors are connected, can be used.

In conclusion, we note that a trained specialist should assemble the electric motor reverse circuit. However, when connecting independently, you must comply with the safety conditions, select suitable connection diagram and select the necessary components, strictly following the instructions for installation. In this case, the designer will not have any difficulties in connecting and operating the electric motor.

Now you know what a reverse of an electric motor is and what connection schemes are used for this. We hope the information provided was useful and interesting for you!

Related materials:

• How to make the simplest electric motor with your own hands
• What is the difference between alternating current and direct current
• What is phase, zero and ground