Views: 0 Author: Site Editor Publish Time: 2022-04-03 Origin: Site
You can perform many different tests on the motor-that's why it's important to know the purpose of these tests, how they work and what the data means. We will first briefly review why the test is important, then discuss the rotor bar, withstand voltage, surge and motor winding resistance, and discuss vibration analysis. Give your ac motor a test!
This passage is going to talk about the followings of test ac motor:
(1) Use belt or pulley to reduce speed
(2) Reduce rpm of dc motor
(3) Reduce rpm of ac motor
The operation of a shaft driven by an electric motor or internal combustion engine or other form of power is characterized by the speed, torque and position of the shaft. Loads driven by shafts often require different speeds or torques, or need to transmit power to adjacent shafts. Reducing RPM can be achieved by using two or more pulleys and belts to transfer and change the rotation speed.
Measure and record the key characteristics of the system. To design a pulley system to reduce the RPM of the power shaft, you will need shaft speed, shaft diameter, distance from power shaft center to load shaft center, load shaft diameter and required load shaft speed. If neither the power shaft nor the load shaft can move, a tensioning wheel is needed to keep the belt at the proper tension. Purchase and install pulleys and belts. If the speed of the load shaft is critical, purchase an adjustable pulley that is fixed together by two halves, which will be used for the power shaft. When the bolt is tightened, the two halves move closer, and the effective diameter of the pulley increases, so the speed can be slightly adjusted.
The pulley represents a simple machine used for many operations. The pulley system consists of two pulleys on the shaft, and the belt connects the pulleys together. One pulley is the driving pulley and the other is the driven pulley. The pulley can change the speed, provide torque and change the direction of rotation. Changing the speed with a pulley requires changing the diameter of the pulley.
Taking the shunt-excited Dc motor as an example, the following three methods can be used to reduce the speed:
(1) Reduce the terminal voltage. Since the power supply voltage is generally fixed, it is difficult to change. Moreover, reducing the terminal voltage will result in a decrease in the excitation current, and therefore will increase the speed of the motor, so this method is rarely used.
(2) Increasing the excitation current means increasing the intensity of the magnetic field. Due to the limitation of the saturation of the magnetic circuit, the power supply voltage is difficult to increase, and the inherent resistance of the field winding cannot be changed, so this method is not widely used.
(3) Connect resistors in series in the armature circuit to reduce the armature end voltage. This method is the simplest and easy to implement, so it is the most commonly used method to reduce the speed of a Dc motor.
The speed of the motor is determined by the number of winding groups. For example, a 4-pole motor (refers to a motor with two pairs of magnetic poles of the motor). When the frequency is 50 Hz, the rated speed is 1450 rpm. When the number of poles is fixed, the most convenient way to adjust the motor speed is frequency conversion. That is to say, as long as you add a frequency converter, you can change the speed of the motor. This speed adjustment can be stepless, and relatively few changes to the machine. However, because the fixed-speed motor cooling fan is fixed on the motor shaft. So after turning down the speed, the fan speed is also reduced. The frequency conversion motor fan is powered separately, and the change of the motor speed does not affect the cooling fan speed. So, in fact, this still needs to be changed slightly to avoid burning the motor. The final output speed change can be achieved with a gearbox.