What are the speed control methods for DC motors?

A device to regulate the speed of the DC motor, the upper end and AC power supply connection, the lower end and DC motor connection, DC governor will be converted to AC power into two output DC power supply, one way input to the DC motor tonearm (stator), all the way input to the DC motor armature (rotor), DC governor through the control of armature DC voltage to adjust the rotational speed of the DC motor, the industry's commonly used brand is the continental 590 Governor.

What is a DC governor

At the same time, the DC motor gives a feedback current to the governor, the governor according to the feedback current to determine the speed of the DC motor, if necessary, correct the armature voltage output, in order to regulate the speed of the motor again.

Speed regulation scheme

1. change the armature voltage; (the longest used one programme)

2. change the excitation winding voltage.

3. change the armature circuit resistance.

DC speed regulation is divided into three kinds: rotor string resistance speed regulation, voltage regulation, weak magnetic speed regulation.

Advantages of DC motor:

1 wide speed range, easy to adjust smoothly

2 overload, starting, braking torque is large

3 easy to control, high reliability

4 less energy loss when speed regulation

Disadvantages: difficult commutation, maintenance is more troublesome, high manufacturing cost (compared with the same power of AC asynchronous motor.

DC governor use conditions

1. Altitude of not more than 1000 metres. (More than 1000 metres, the rated output current value is reduced)

2. Ambient temperature not higher than 40℃ and not lower than -10℃.

3. The relative humidity of the surrounding environment is not greater than 85 [%], no water condensation droplets.

4. There is no significant vibration and bumpy occasions.

5. There is no danger of explosion in the surrounding medium, and there is no gas or conductive dust that is sufficient to corrode the metal and destroy the insulation.

6. Indoor use

DC governor technical data

1. Input mains voltage: AC three-phase 380V50HZ

2. Allowable difference of grid voltage: -5[%]--10[%].

3. Allowable difference of grid frequency: + -2[%].

DC governor applications

Machine tool applications: work drive motors for gantry planers, rail grinders, gantry milling machines, etc., spindle motors for rail grinders, boring machines, milling machines, etc., which are usually used in these industries with the Eurofins 590 DC governor.

First, the basic principle of DC motor speed regulation

The basic principle of DC motor speed control is to change the motor voltage or current, thereby changing the motor torque and speed. Commonly used speed control methods include resistance speed control, excitation speed control, PWM speed control and vector control speed control.

Second, resistance speed control

Resistance speed control is a simple and effective speed control method, which changes the motor speed by changing the resistance of the motor armature circuit. The specific implementation method is to connect a certain resistance in series in the motor armature circuit, with the increase of resistance, the current of the motor armature circuit decreases, thus reducing the speed of the motor. In practice, according to the characteristic curve of the motor and load characteristics to choose the appropriate resistance value to achieve the effect of speed regulation.

Third, excitation speed regulation

Excitation speed regulation is to change the motor speed by changing the motor excitation current. In DC motors, the size of the excitation current determines the torque and speed of the motor, so changing the excitation current can achieve the purpose of speed regulation. The specific implementation method is to adjust the excitation current by changing the resistance in the excitation circuit or changing the voltage of the excitation power supply.

Fourth, PWM speed regulation

PWM speed control is a new type of speed control method, which can achieve speed control by changing the duty cycle of motor voltage. The specific implementation method is to regulate the power supply voltage through the PWM controller, the voltage is divided into a number of cycles, the duty cycle of the voltage in each cycle is different, so as to achieve the control of the motor speed.PWM speed control has a wide range of speed, high efficiency, fast response speed and other advantages, so it has been widely used in industrial production.

V. Vector control speed regulation

Vector control speed regulation is a kind of speed regulation method, which can achieve the control of motor speed, torque and power. The core of vector control speed regulation is to add vector control algorithm in the motor controller. Vector control speed regulation has the advantages of fast response speed, high precision, wide range of application, etc., and is currently the advanced DC motor speed regulation technology.

There are various methods of motor speed regulation, the following is a list of several common methods and their principles:

1. Voltage modulation speed regulation: this is one of the simplest and most common methods of speed regulation. The speed of the motor is controlled by changing the supply voltage of the motor. Decreasing the voltage reduces the speed of the motor and increasing the voltage increases the speed of the motor. This method is applicable to DC motors and some AC motors.

2. Pulse Width Modulation (PWM) Speed Control: This method of speed control controls the speed of the motor by varying the duty cycle of the supply voltage. The average voltage value of the motor is controlled by periodically changing the ratio of high and low level time of the supply voltage, thus controlling the speed of the motor. This method is widely used in DC motors and three-phase AC motors.

3. Inverter speed control: This is a frequency converter-based speed control method for AC motors. The frequency converter converts the fixed-frequency alternating current (AC) of the power supply into adjustable-frequency and adjustable-voltage AC, and controls the speed of the motor by changing the frequency and voltage. This method has high accuracy and effect of speed regulation and is widely used in industrial fields.

4. Pole number speed regulation: For some AC motors, speed regulation is achieved by changing the number of pole pairs of the motor. By changing the winding connection of the motor or changing the number of magnetic poles mechanically, the speed of the motor can be changed.

5. Feedback control speed regulation: This method of speed regulation measures the actual speed of the motor by using a feedback device (e.g., an encoder or a speed sensor) and compares it with the desired speed, and then regulates and controls it according to the comparison. The feedback signal can be used in a closed-loop control system, allowing the motor to adjust its output in real time to achieve the desired speed.

These methods are only common motor speed control methods, and the specific method to be used will depend on the type of motor, application scenario and requirements. Each speed control method has its own specific principle and scope of application, you need to choose the appropriate method to achieve motor speed control according to the actual situation.