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As a new type of high-efficiency energy-saving product, the permanent magnet synchronous motor has been widely recognized and developed rapidly. With the continuous development of science and technology, contemporary people’s requirements for motor cooling systems are also increasing. Because the temperature rise of the motor is often caused by the high-temperature rise of the coil, it will also affect the key aspects of the motor use time, stability, and energy efficiency.
There are many cooling methods for motors. According to different cooling media, they can be classified into air cooling, water cooling, oil cooling, and hydrogen cooling.
Air cooling refers to the way heat dissipation mainly relies on the airflow inside the motor. Generally, the inside of the motor is a relatively sealed space containing a certain volume of air. The rotor is rotated to force the air to flow, and the cold air sweeps over the coil to take away the heat from the motor coil and iron core. The hot air exchanges heat with the outside world through the heat dissipation channel. The air cooling system has the advantages of simple structure, low cost, convenient maintenance, and stable operation. When the air volume is insufficient, the heat dissipation capacity is relatively low, and the efficiency of the motor is reduced due to the ventilation loss.
Water cooling is one of the ways of liquid cooling. The different cooling parts can be divided into two ways: stator water cooling and rotor water cooling. High-power winding linear motors mostly use water-cooling systems. Generally, slots are slotted at the bottom of the windings, and cooling water pipes are set to circulate and reciprocate to take away the heat of the windings and the iron core, and exchange heat in the cooler. Water has a high specific heat capacity and a strong cooling capacity.
Oil cooling is another form of liquid cooling. Unlike the cooling medium water, oil has a higher dielectric constant, so it can be cooled by pipes like water cooling, or it can be cooled by direct contact with higher-temperature windings and iron cores. , but the purity of the oil must be high, otherwise, once impurities are introduced, the insulation between the windings and coils may be damaged when the motor is cooled by oil, and the motor will be directly burned.
Hydrogen has unique advantages as a cooling medium, and the ventilation loss is only 1/10 of that of air cooling under the same pressure and temperature conditions. Generally, several hollow stainless steel tubes are clamped in the coil winding. Hydrogen flows through the steel pipe to remove heat. The advantage of hydrogen cooling is that the cooling effect is very good, and the noise is low. The disadvantage is that the system structure is complicated and the maintenance is inconvenient. Moreover, hydrogen is explosive and prone to accidents.
