DC motor speed control method
One is to adjust the armature voltage and the other is to adjust the excitation current.
1. Common miniature DC motors whose magnetic fields are fixed, non-adjustable permanent magnets,
So you have to adjust the armature voltage.
Adjust the armature voltage method:
One of the most commonly used is the thyristor voltage regulator method, and the pulse width modulation method (PWM).
The PWM type H belongs to speed regulation. The PWM H-bridge can only achieve high power speed regulation. The domestic super power speed control also depends on the thyristor to realize the controllable rectification to realize the voltage regulation and speed regulation of the DC motor.
2, weak magnetic speed control, by appropriately weakening the method of excitation magnetic field can also speed.
Second, DC motor and AC motor speed comparison
The biggest advantage is that the DC motor can realize "smooth and economical speed regulation"; the speed regulation of the DC motor does not need the cooperation of other equipment, and can be adjusted by changing the input voltage/current, or the excitation voltage/current.
The timing of AC permanent magnet synchronization is achieved by changing the frequency and requires a frequency converter.
Although the DC motor does not need other equipment to help speed control, its own structure is complicated and the manufacturing cost is high. Before the large-capacity controllable thyristor is used in large quantities, the DC motor is used in most of the speed control applications. After the industrialization of high-power controlled thyristors, the speed regulation of AC motors has become simpler, and the advantages of AC motors, such as low manufacturing cost and long service life, have been demonstrated.
Third, the advantages and disadvantages of DC motor speed control methods
Different needs, using different speed control methods, should have their own characteristics.
1. In the all-magnetic state, adjust the armature voltage, which is suitable for speed regulation in the range from zero to base speed. The maximum speed of the motor cannot be reached.
2. In the armature full voltage state, adjust the excitation voltage, which is suitable for application above the base speed, and weak magnetic acceleration. The lower speed of the motor cannot be obtained.
3. In the state of full magnetic field, after adjusting the armature voltage and the full voltage of the armature, the magnetic field weakens. Suitable for applications with large speed range. This is the most complete DC motor speed control method, but the equipment is complex and the cost is high.