What are the advantages and disadvantages of high voltage motors compared to low voltage motors?

What are the advantages and disadvantages of high voltage motors compared to low voltage motors?

For AC motors, high voltage motors with rated voltages of 1000V and above; low voltage motors of less than 1000V (the limit in some materials is 1140V). For DC motors, high voltage motors with rated voltages above 1500V and low voltage motors with rated voltages below 1500V. Then, what are the advantages and disadvantages of high voltage motors compared to low voltage motors:

The rated voltage is different, the starting and working current are different, the higher the voltage, the smaller the current; the insulation and withstand voltage of the motor are different, the wire of the motor winding is the same, the motor of the same power, the motor wire of high voltage is lower than the voltage There are fewer, and the cables used are different.

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Main difference in structure:

First, the insulation material of the coil is different. Low-voltage motors, coils mainly use enameled wire or other simple insulation, such as composite paper. The insulation of high-voltage motors usually adopts multi-layer structure, such as powder mica tape, the structure is more complicated, and the pressure resistance is higher.

Second, the difference in heat dissipation structure, low-voltage motor mainly uses coaxial fan to blow heat, most of the high-voltage motor has an independent radiator, usually two kinds of fans, one set of internal circulation fan, one set of external circulation fan, two The group fans operate at the same time, and heat exchange is performed on the radiator to discharge heat from the outside of the motor.

Third, the bearing structure is different. Low-voltage motors usually have a set of bearings in front and rear. However, because of the heavy load, high-voltage motors usually have two sets of bearings at the shaft end. The number of non-shaft-extending bearings depends on the load, and is particularly large. The motor will use a sliding bearing.

Advantage:

(1)  High-voltage motors can do a lot of power, up to thousands or even tens of thousands of kilowatts. This is because, at the same output power, the current of the high-voltage motor can be much smaller than that of the low-voltage motor (essentially inversely proportional to the voltage), for example, the rated current of a 500 kW, 4-pole motor, and about 900 A when the rated voltage is 380 V. When the rated voltage is 10kV, it is only about 30A. Therefore, the high voltage motor winding can be used with a smaller wire diameter. As a result, the stator copper loss of the high voltage motor is also less than that of the low voltage motor. For high-power motors, when low-voltage power is used, a large-area stator slot is required due to the need for a thicker wire, so that the stator core diameter is made large and the entire motor volume is large.

(2) For large-capacity motors, the power supply and power distribution equipment used in high-voltage motors have less overall investment than low-voltage motors, and the line loss is small, which can save a certain amount of power consumption. In particular, the high-voltage motor of 10kV can directly use the network power supply (the high-voltage power supplied to users in China is generally 10kV), so that the investment in the power supply equipment (mainly the transformer) will be less, and the use is also simpler. It will be less.

Disadvantage:

(1) The cost of the winding is relatively high (mainly caused by insulation), and the associated insulation material cost will also be higher.

(2) The insulation treatment process is difficult and the labor cost is high.

(3) The requirements for the use environment are much stricter than for low-voltage motors.

 


Post time: Aug-19-2019

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