What are the advantages and disadvantages of high-voltage motors compared with low-voltage motors?
For AC motors, those with a rated voltage of 1000V and above are high-voltage motors; those with a rated voltage of less than 1000V are low-voltage motors (the limit in some materials is 1140V). For DC motors, those with a rated voltage of 1500V and above are high-voltage motors; those with a rated voltage below 1500V are low-voltage motors. So, what are the advantages and disadvantages of high-voltage motors compared with 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 also different, the wires of the motor windings are also the same, the same power motor, the high voltage motor wire is lower There are fewer cables, and the cables used are different.
The main difference in structure
First, the insulation materials of the coils are different. For low-voltage motors, the coils mainly use enameled wire or other simple insulation, such as composite paper. The insulation of high-voltage motors usually adopts a multilayer structure, such as powder mica tape, which has a more complex structure and withstand voltage. higher.
Second, the difference in heat dissipation structure. Low-voltage motors mainly use coaxial fans for direct cooling. Most high-voltage motors have independent radiators. There are usually two types of fans, one set of internal circulation fans, one set of external circulation fans, and two The group fans operate at the same time, and conduct heat exchange on the radiator to remove the heat from the motor.
Third, the bearing structure is different. Low-voltage motors usually have one set of bearings at the front and rear. For high-voltage motors, because of the heavy load, there are usually two sets of bearings at the shaft extension end. The number of bearings at the non-shaft extension end depends on the load. The motor will use sliding bearings.
(1) High-voltage motors can be made with great power, up to several thousand or even tens of thousands of kilowatts. This is because, at the same output power, the current of a high-voltage motor can be much smaller than that of a low-voltage motor (basically, it is inversely proportional to the voltage). For example, the rated current of a 500kW, 4-pole motor is about 900A when the rated voltage is 380V. When the rated voltage is 10kV, it is only about 30A. Therefore, a smaller wire diameter can be used for high-voltage motor windings. Therefore, the stator copper loss of the high-voltage motor will be less than that of the low-voltage motor. For a higher-power motor, when using low-voltage electricity, a large area of the stator slot is required due to the need for a thicker wire, so that the stator core diameter is made large, and the entire volume of the motor is also large.
(2) For larger-capacity motors, the power supply and power distribution equipment used by high-voltage motors has less overall investment than low-voltage motors, and the line loss is small, which can save a certain amount of power consumption. Especially the 10kV high-voltage motor can directly use the network power supply (the high-voltage power provided to users in our country is generally 10kV), so that the investment in power equipment (mainly transformers) will be less, the use is easier, and the failure rate It will be less.
(1) The cost of winding is relatively high (mainly caused by insulation), and the cost of related insulation materials will also be high.
(2) The insulation treatment process is difficult, and the man-hour costs are high.
(3) The requirements for the use environment are much stricter than low-voltage motors.