A Brief Discussion on DC Motor Speed ​​Regulation

Characteristics of DC motor speed regulator voltage regulation:

1. The artificial characteristic of voltage reduction is a straight line parallel to the inherent characteristic, and there is an obvious speed regulation effect regardless of full load, light load or no load.

2. Due to the constant hardness of the artificial characteristics, the speed fluctuation caused by load changes at low speed is not large. The static stability is good and the adjustment range is large.

3. The terminal voltage can be adjusted smoothly, the speed can be adjusted smoothly, and stepless speed regulation can be achieved.

4. The energy loss during the adjustment process is small.

Speed ​​control by changing the armature circuit resistance:
Keeping U＝UN, Φ＝ΦN unchanged, inserting a speed control resistor Rc in series into the armature circuit, so that the same load can obtain different speeds, is called armature series resistance speed control. The larger the resistance in series into the armature circuit, the lower the speed.

The speed at which the motor runs on its inherent mechanical characteristics is called the base speed. The speed control method of adding resistance in series to the armature circuit can only be adjusted downward from the base speed. Changing the transmission ratio of the transmission mechanism to change the speed of the working mechanism is called mechanical speed control.
Artificially changing the motor parameters (such as terminal voltage, excitation current and armature circuit resistance) to obtain different speeds for the same mechanical load is called electrical speed control.
When the motor drives the production machinery, the speed of the motor must not only be adjustable, but also have a wide range of adjustment, a smooth process, and a simple and economical adjustment method.

The speed regulation formula of DC motor:
n＝〔U－Ia（Ra＋Rj）〕/CeΦ

DC motor controller method:
1. Change the excitation current to change the magnetic flux.
2. Change the voltage U applied to the two ends of the armature.
3. Change the regulating resistor in series with the armature circuit.

Changing the excitation speed regulation:
Changing the excitation current speed regulation is actually reducing the excitation current speed regulation, also known as weak magnetic speed regulation.
Weak magnetic speed regulation: Keep U = UN, Rj = 0, only reduce the excitation current If of the motor to reduce the main magnetic flux, to achieve the purpose of speed regulation.