Application of relay in Brushless DC motor control

Relay is one of the common components in electrical control system, which is widely used in various motor control fields. In the control of Brushless DC motor, the role of relay is particularly important. It can adjust the start stop, steering, speed and other functions of the motor through the control circuit

what is a relay

A relay is an electrical component used to control a circuit switch. Through the electromagnetic principle, the relay can control the switch of high-voltage circuit under the action of low-voltage signal. The relay is usually composed of coil, contact and iron core. When the coil is energized, the magnetic field makes the iron core attract or push the contact, so as to realize the closing or breaking of the circuit.

Overview of brush DC motor

Brush DC motor (abbreviated as brush DC motor) is a kind of motor that uses the contact between brush and commutator to switch the direction of current. Its working principle is relatively simple, but due to mechanical friction, its efficiency and life are slightly lower than that of brushless motor. However, because of its simple structure and low cost, it is still widely used in small household appliances, automotive power tools and other fields.

The basic function of relay in the control of Brushless DC motor

The main function of relay in the control system of Brushless DC motor is to control the start and stop, direction reversal and other electrical characteristics of the motor through electrical signals. The relay controls the connection or disconnection of the motor circuit through the current switch, so as to realize the regulation of the motor. Specifically, relays play a role in:

Start stop control of motor

The power supply of the motor can be controlled through the relay to realize the start and stop of the motor. In some simple motor control systems, the relay is used as a switch to directly control the operation of the motor by connecting or disconnecting the power supply of the motor.

Reverse control of motor

In the brushless DC motor, the common method to control the rotation direction of the motor is to reverse the polarity of the motor power supply. The relay can control the rotation direction of the motor by switching the current direction in the circuit to realize the forward or backward movement of the motor.

Speed adjustment of motor

In some brushless DC motor control systems, the relay indirectly adjusts the motor speed by adjusting the input frequency of the motor power supply. Although this speed regulation mode is not as accurate as PWM control, relay can provide certain speed regulation function in some low-cost or simple applications.

The wiring in the figure above is the principle of motor control. Two SPDT relays are used to connect the motor. The default connection makes the motor in the brake state, so that the energy can be quickly released to the ground when the motor is turned off. The two relays are essentially used as four controllable switches.

Application of relay in the control of Brushless DC motor

Application in household appliances

In many household appliances, such as fans, washing machines, vacuum cleaners, etc., relays are used to control the start, stop and reverse operation of motors. For example, in a washing machine, the relay controls the forward and reverse rotation of the motor to complete the

washing and dehydration process.

Application in electric tools

Electric tools such as electric drills and electric screwdrivers are often driven by brush DC motors. The application of relay in these tools is mainly to control the start, stop, reverse and switching of different working states of the motor. For example, in an electric drill, the relay controls the positive and negative rotation of the motor for drilling or withdrawal.

Application in robot

In robot control system, brushless DC motor is often used for motion drive, and relay is responsible for the direction and speed control of motor in this kind of system. The robot can change the direction of motion by switching the polarity of the motor power supply through the relay, or use the relay combination to control the movement of multiple motors.

Application in electric vehicle

In some low-speed electric vehicles (such as electric scooters, electric bicycles, etc.), brush DC motors are used for driving. The application of relay in this kind of electric vehicle includes the control of motor start, stop and speed regulation.

Choosing a good relay product can improve the effective protection of electrical and motor. Qianji is a professional relay manufacturer, providing high-quality and low-cost relay products and producing all types of relays. If you are interested, you can visit the relay category, or consult us for information. Qianji can solve the problems of long procurement time, troublesome selection and poor after-sales service for you

Comparison between relay and other control equipment

Compared to other control devices, like MOSFET, SCR, etc., relay shows obvious advantages and disadvantages in the control of the Brushless DC motor. Relay suits the application occasion of low cost and simplicity, but MOSFET or PWM controller is more powerful for high-speed high-precision control.

summary

As a mature and cheap electronic control component, the relay plays an important role in controlling the start and stop, reverse control, speed regulation and other aspects of Brushless DC motor. With the continuous progress of science and technology, the performance of the relay continues to improve. In the near future, it will face a broader application in more fields.