The difference between the frequency converter and the ordinary motor
The structure design Structure design, main is also considering the non-sinusoidal power characteristics of variable frequency motor insulation structure, the influence of vibration and noise cooling mode, generally pay attention to the following questions: 1) insulation level, which is generally F or higher, strengthens the insulation strength of the ground and turns, especially considering the ability of insulation to withstand shock voltage. 2) to the problem of vibration and noise of the motor, the motor should be fully considered component and overall rigidity, trying to improve its natural frequency, in order to avoid and every force wave resonance phenomenon. 3) cooling mode: the general adoption of forced ventilation cooling, the main motor cooling fan is driven by an independent motor. To prevent shaft current measures, the bearing insulation measures should be applied to the capacity exceeding 160KW motors. Mainly produces magnetic circuit asymmetry, also can produce shaft current, while the rest of the high frequency component generated by the current role in combination, shaft current will increase greatly, which can lead to bearing damage, so often insulation measures. For constant power frequency converter motor, the special lubricating grease should be used to compensate the temperature of the bearings when the speed is over 3000 / min.
There is no difference between the motor and the motor of the converter is the three-phase asynchronous motor. However, the speed of the machine can be adjusted to achieve energy saving and constant pressure.
The difference between the frequency conversion motor and the ordinary motor is that the converter motor has no cooling fan, and it needs to be cooled by the fan. Ordinary motors rely on their own fans for heat dissipation, and running maintenance is relatively simple.
Variable frequency motor is more than ordinary motor, and the specific advantages of frequency conversion motor are: 1, have the start function The resistance of stator and rotor is reduced by electromagnetic design Adjust to the constant speed change under different working conditions 4, to some extent energy saving
Electromagnetic design 'for common asynchronous motors, the main considerations in redesigning are overload capacity, startup performance, efficiency, and power factor. And frequency conversion motor, because of the critical slip inverse ratio at power frequency, you can directly start when critical slip is close to 1, therefore, overload capacity and startup performance is not need to think too much, and to solve the key problem is how to improve the ability to adapt the motor of the non sine wave power. Here's how it works: Minimize stator and rotor resistance as much as possible. Reducing the stator resistance can reduce the copper consumption of the base wave to compensate for the increase in the copper consumption caused by higher harmonic waves." In order to suppress the high harmonics in the current, the inductance of the motor is needed. However, the main effect of the rotor slot leakage resistance is large, and the high frequency harmonic copper consumption increases. Therefore, the size of the leakage resistance of the motor should be adjusted to the rationality of the impedance matching within the entire speed limit. ; 3) the main magnetic circuit of frequency conversion motor generally designed to unsaturated state, one is to consider will deepen higher harmonic magnetic circuit saturation, 2 it is to consider at low frequency, in order to improve the output torque and appropriate to increase the output voltage of inverter.
