The three-phase asynchronous motor test bench is a device that converts electromechanical energy into mechanical energy through the interaction between the rotating magnetic field and the induced current of the rotor coil through an air gap. According to the rotor structure of the motor, it can be divided into two types: squirrel cage and wound asynchronous motors. A servo motor is an electric motor used to assist in indirect gear shifting of an electric motor, which is used to control the operation of mechanical components in a servo system. This system can achieve precise control of the speed and position of the motor, and can convert voltage signals into torque and speed, thereby driving the target.
The following compares the performance of two types of motors.
1、 Differences in Control Accuracy
The step angle of a three-phase hybrid stepper motor is generally 3.6 ° and 1.8 °, while that of a five phase hybrid stepper motor is generally 0.72 ° and 0.36 °. The step angle of the electric motor should be smaller. A rotary encoder is installed at the rear of the motor to ensure its control accuracy. AC servo motor, using a standard 2500 line encoder, with a pulse equivalent of 360 °/10000=0.036 °. In a 17 bit encoder motor, this driver program rotates once every 217=131072 pulses received, resulting in an equivalent output of 360 degrees/131072=9.89 seconds. This is 1/655 of the equivalent pulse of the stepper motor, with a step length of 1.8 degrees.
2、 Different low-frequency characteristics
The three-phase asynchronous motor test bench is prone to low-frequency vibration at low speeds. The vibration frequency is related to the load condition and the performance of the driver. It is generally believed that the vibration frequency is half of the no-load take-off frequency of the motor. This low-frequency vibration phenomenon determined by the working principle of the motor is very detrimental to the normal operation of the machine. When a stepper motor operates at low speeds, damping techniques should generally be used to overcome low-frequency vibration phenomena, such as adding dampers to the motor or using subdivision techniques on the driver.
The AC servo motor runs very smoothly, and there is no vibration even at low speeds. The communication servo system has resonance suppression function, which can cover the insufficient rigidity of machinery, and the system has frequency analysis function (FFT) inside, which can detect the resonance point of machinery and facilitate system adjustment.
3、 Different moment frequency characteristics
The output torque of the three-phase asynchronous motor test bench decreases with increasing speed, and sharply decreases at higher speeds, so its maximum operating speed is generally between 300-600 RPM. AC servo motors have constant torque output, which means they can output rated torque within their rated speed (usually 2000RPM or 3000RPM), and constant power output above the rated speed.
4、 Different overload capacities
Three phase asynchronous motors generally do not have overload capacity. AC servo motors have strong overload capacity.