Special design of frequency conversion motor

The application of frequency conversion motor in production is very extensive, so what special about his design?

电磁设计

Electromagnetic design

对普通异步电动机来说，在设计时主要考虑的性能参数是过载能力、启动性能、效率和功率因数。而变频电动机，由于临界转差率反比于电源频率，可以在临界转差率接近1时直接启动，因此，过载能力和启动性能不在需要过多考虑，而要解决的关键问题是如何改善电动机对非正弦波电源的适应能力。方式一般如下：

For the ordinary asynchronous motor, the main parameters considered in the design are overload, starting performance, efficiency and power factor.. And frequency conversion motor, due to the critical slip ratio is inversely proportional to the power supply frequency can in critical slip ratio close to 1 started directly. Therefore, overload capacity and start-up performance not excessive considering. In order to solve the key problem is how to improve the adaptability of non sinusoidal wave power of the motor. The way is generally as follows:

1）为抑制电流中的高次谐波，需适当增加电动机的电感。但转子槽漏抗较大其集肤效应也大，高次谐波铜耗也增大。因此，电动机漏抗的大小要兼顾到整个调速范围内阻抗匹配的合理性。

1) in order to restrain the higher harmonic in current, the inductance of the motor should be increased.. But the leakage of the rotor slot is larger and the skin effect is higher, and the higher harmonic copper consumption is also increased. Therefore, the size of the leakage reactance of the motor should be balanced with the rationality of the impedance matching in the speed range..

2）变频电动机的主磁路一般设计成不饱和状态，一是考虑高次谐波会加深磁路饱和，二是考虑在低频时，为了提高输出转矩而适当提高变频器的输出电压。

2) variable frequency motor of main magnetic circuit design into unsaturated state, is considering harmonic will deepen saturation of magnetic circuit, the second is to consider at low frequencies, in order to improve the output torque and appropriate to increase the output voltage of the inverter.

3）尽可能的减小定子和转子电阻。

3) reduce the stator and rotor resistance as much as possible.

减小定子电阻即可降低基波铜耗，以弥补高次谐波引起的铜耗。

Reducing the stator resistance can reduce the base copper loss, and can compensate the copper loss caused by high harmonics..

结构设计

Structure design

在结构设计时，主要也是考虑非正弦电源特性对变频电机的绝缘结构、振动、噪声冷却方式等方面的影响，一般注意以下问题：

In the structural design, the main consideration is the non sinusoidal power supply characteristics of the inverter motor insulation structure, vibration, noise cooling mode, etc., the following questions are generally attention:

1）对电机的振动、噪声问题，要充分考虑电动机构件及整体的刚性，尽力提高其固有频率，以避开与各次力波产生共振现象。

1) for the vibration and noise problem of the motor, the rigidity of the motor component and the whole is considered, and the natural frequency of the motor is improved, and the resonance phenomenon of the motor is avoided..

2）对恒功率变频电动机，当转速超过3000r/min时，应采用耐高温的特殊润滑脂，以补偿轴承的温度升高。

2) for the constant power frequency conversion motor, when the speed exceeds 3000r/min, the special grease that should be used for high temperature is used to compensate the temperature of the bearing..

3）绝缘等级，一般为F级或更高，加强对地绝缘和线匝绝缘强度，特别要考虑绝缘耐冲击电压的能力。

3) insulation grade, generally F grade or higher, strengthen the insulation and wire turn insulation strength, in particular, to consider the insulation impact resistance.

4）冷却方式：一般采用强迫通风冷却，即主电机散热风扇采用独立的电机驱动。

4) cooling mode: the general use of forced ventilation cooling, that is, the main motor cooling fan using independent motor drive.

5）防止轴电流措施，对容量超过160KW电动机应采用轴承绝缘措施。主要是易产生磁路不对称，也会产生轴电流，当其他高频分量所产生的电流结合一起作用时，轴电流将大为增加，从而导致轴承损坏，所以一般要采取绝缘措施。

5) to prevent shaft current measures, the capacity of the motor to exceed 160KW should adopt bearing insulation measures. Is mainly easy to produce magnetic circuit asymmetry, shaft current, when the other frequency component generated currents combined together, shaft current will be greatly increased, resulting in damage to the bearings, so in general to take insulation measures.