There are three types of servo motor controllers introduced

The types of servo motor controllers include three categories: step-down starter, speed control drive, and intelligent controller. In addition, the control is mainly carried out in two ways: square wave control and sine wave control. The following is a detailed introduction to the relevant content.

1. Types of servo motor controllers

1. Reduced voltage starter

Two or more contactors can be used to provide a lower voltage when the motor is started. Using an autotransformer or series inductor, a lower voltage can be input to the terminals when the motor is started, reducing the starting torque and inrush current. When the motor speed reaches a certain percentage of the rated speed, the starter automatically switches the motor terminals to normal voltage input. Because the autotransformer and series inductor only have a heavy starting current flowing through them at startup, which may only last for a few seconds, their ratings are smaller than the ratings for the same current under continuous use. The switch from lower voltage to normal voltage can be switched by time timing, or with a current sensor, when the current begins to drop.

2. Speed ​​​​regulating drive

A variable speed drive or variable speed drive is a device that adjusts the speed of a mechanical load. A variable speed drive consists of a motor, a speed controller or power converter, and auxiliary equipment or instruments. However, generally speaking, the word drive is only used to refer to the controller. Many newer variable speed drives can also perform motor soft starting.

3. Intelligent controller

Intelligent controllers use microprocessors to control the power components used in motor control. They can also monitor the motor load and match the motor torque to the load. This is done by reducing the AC voltage to the motor, while reducing the current and reactive power. Therefore, if the motor is operated under light load conditions for a long time, the above method can measure the improvement in energy efficiency. At this time, the heat, noise and vibration generated are also reduced.

2. Control method of servo motor controller

1. Square wave control is often called six-step control.

2. Sine wave control is called SPWM drive. Strictly speaking, FOC is also called sine drive, but the control object of SPWM is voltage, while the control object of FOC is current. According to the complexity of control, the sine wave control of brushless DC motor can be divided into simple sine wave control and complex sine wave control.

(1) Simple sine wave control: A certain voltage is applied to the motor winding to make the motor phase voltage a sine wave. Since the motor winding is an inductive load, the motor phase current is also a sine wave. By controlling the amplitude and phase of the motor phase voltage to control the phase and amplitude of the current, it is called voltage loop control, which is relatively simple to implement.

(2) Complex sinusoidal control: Different from simple sinusoidal control, complex sinusoidal control targets the motor phase current, establishes a current loop, and achieves the purpose of controlling the motor by directly controlling the phase and amplitude of the phase current. Since the motor phase current is a sinusoidal signal, it is necessary to perform current decoupling operations, which is relatively complex. Common ones include field oriented control (FOC) and direct torque control (DTC).