What’s the high voltage AC Motor

High-voltage AC Motor start ways:

1, autotransformer decompression start and reactor buck start compared to get the same starting torque in the case of autotransformer-type step-down start of the start-up current is small, suitable for large resistance torque situation.

2, the motor full pressure start when the high current in the stator coil and rotor rod cage to produce a great impact, will damage the winding insulation and cause the cage crack, causing the motor failure, high current will produce a lot of Joule heat , Damage the winding insulation, reduce motor life.

3, water resistance and liquid resistance of the type of soft-start device, water resistance is the movement of the plate and the high current so that the water vaporization (plate surface) to form a high resistance to change the resistance of the liquid to control the starting current (voltage), and liquid Variable resistance is dependent on the number of impurities, the size of the plate and the high current to the plate near the water vaporization of the high resistance to control the start.

4, the ordinary squirrel-cage motor in the no-load full pressure directly start, the starting current will reach the rated current 4-7 times. When the motor capacity is relatively large, the starting current will cause a sharp decline in the grid voltage, voltage and frequency will change, which will destroy the other equipment with the normal operation of the grid, and even cause the grid to lose stability, resulting in greater accidents.

5, series reactor start for a step-down start, in the full pressure switch torque jump, will have a mechanical impact. The probability of operating an overvoltage is less than a direct full pressure start. However, due to the randomness of high-frequency oscillation, large-scale operation of the over-voltage is still possible.

6, the use of thyristor technology in the medium voltage motor soft start device on the components of the consistency of the parameters of the requirements of a high element, the screening rate of components is very low, and the high price of screening equipment, which makes the device price high. Also in the use of a period of time, the components of the parameters will change, so that components of the uniformity of performance, can easily lead to damage to the entire string of components, so that the reliability of such devices.

7, the switch transformer medium voltage motor soft start device is to use the switching transformer to isolate the high voltage and low voltage, switching transformer low voltage winding connected with the SCR and control system, by changing its voltage on the low voltage winding to change the voltage on the high voltage winding , So as to achieve the purpose of changing the motor terminal voltage to achieve the soft start of the motor. During the start-up process, the switching transformer is always in both on and off working conditions, switching transformer losses are small.

8, with the medium voltage inverter to do the soft start device to start the high voltage motor, its start performance is very good, but the medium voltage inverter is expensive, and the other because the frequency conversion technology is still in the development period, its reliability is not very high, the user's maintenance Technology can not keep up, this is the method is not a lot of reasons, are generally used in imported equipment. With the inverter to start the high-voltage motor, can be done without over-voltage, but the inverter output voltage contains a large number of high-order harmonics, will also cause damage to the motor.