We'll begin today's topic by sharing our personal experiences. Washing machines are a necessity in every household. In the past, each family would have a suitably sized washbasin and washboard. With societal development, we've entered the era of fully automatic washing machines. The perfect combination of the washing machine motor and controller has liberated us from tedious labor. Today, Ms. will discuss motor controllers and provide a brief explanation of inverters.
1. What is a motor controller?
With the development of the electronic age, motor control has gradually evolved from initial manual control to automated intelligent control, thus giving rise to motor controllers. A controller is a command device that controls the starting, speed regulation, braking, and reversing of a motor by changing the wiring of the main circuit or control circuit and altering the resistance values in the circuit according to a predetermined sequence. It consists of a program counter, instruction register, instruction decoder, timing generator, and operation controller. It is the "decision-making body" that issues commands, coordinating and directing the operation of the entire computer system.
2. Advantages of integrated controller
Integrated controllers can be supplied to users as a complete set with the integrated motor body, or they can be supplied separately. Integrated supply facilitates manufacturers' control, inspection, and management of product quality, as well as product packaging, storage, and shipping; it also facilitates users' incoming inspection, storage, and use of purchased products. Integrated controllers are suitable for mechanical devices and equipment that do not have connections with other peripheral systems.
Manufacturers can design controllers specifically to meet users' particular requirements, resulting in a more compact and robust mechanical structure that saves space. In terms of circuitry, they can consider relevant signals from peripheral systems or integrate the controller's circuitry into the overall control system of the user's equipment, facilitating information transmission and feedback. Furthermore, they can comprehensively address electromagnetic compatibility and anti-interference issues, thereby improving the quality of the user's products.
For some low-power motors, the controller can even be enclosed within the motor housing. The pricing for integrated versus modular supply depends on the specific circumstances.
3. Comparison of different inverters
The inverter mentioned here is an electronic commutation (phase) circuit composed of power switching devices. Generally speaking, the inverters used in brushless DC permanent magnet motors and self-controlled permanent magnet synchronous motors are basically of two types: unipolar inverters and bipolar inverters.
A unipolar inverter is a non-bridge electronic commutation (phase) circuit composed of three power switching devices. When a unipolar inverter is used in a motor, the current in the armature winding can only flow in one direction and cannot flow in the opposite direction. This results in low winding utilization; however, during operation, the power supply voltage is consumed only on one power switching device. Therefore, it is suitable for low-power and low-voltage brushless DC permanent magnet motors (BLDCM), and of course, the price is also lower. It can only be used as a controller for two-quadrant operation.
A bipolar inverter is a bridge-type electronic commutation (phase) circuit composed of six power switching devices. Bipolar inverters are available in two types: 120° conduction and 180° conduction. The Hall sensors in these two types differ in phase by 30°. The 120° conduction type inverter is suitable for brushless DC permanent magnet motors (BLDCM); the 180° conduction type inverter forms the basis of sinusoidal pulse width modulation (SPWM) and space vector pulse width modulation (SVPWM), and is suitable for self-controlled permanent magnet synchronous motors (PMSM).
When a bipolar inverter is used in a motor, the current in the armature winding can flow in both directions, resulting in high winding utilization, large output power or torque of the motor, and it can be made into a controller that operates in four quadrants. Of course, the price is also relatively high.
As for the power supply voltage consumed by the two power switching devices when using a bipolar inverter, it will become smaller and smaller with the development of semiconductor technology, and may even be negligible.
