Frequency conversion motor and power frequency motor have what differentiation

Frequency conversion motor and power frequency motor have what differentiation A, the common asynchronous motor all is according to the constant frequency constant pressure design, can't completely adapt to the requirements of the variable frequency speed regulation. The following is a frequency converter to rotary joints the influence of the motor
1, motor efficiency and the problem of temperature rise Regardless of the form of frequency converter, in the operation of all can produce different degree of harmonic voltage and current, make the motor in non-sinusoidal voltage, electric operation flow. Rejected material is introduced, with the current widespread use of sine wave PWM type converter as an example, its low harmonic basic to zero, than the rest of the carrier frequency about twice as large as the high order harmonic component for: 2 u + 1 (u for modulation ratio). High order harmonic can cause motor stator copper loss and rotor copper (aluminum) consumption, iron loss and additional loss increased, most notably rotor copper (aluminum) loss. For asynchronous motor is close to the base wave frequency of the corresponding synchronous speed rotation, therefore, high order harmonic voltage with the larger slip cutting rotor conducting bar, will produce a lot of rotor loss.
In addition, still need to consider for skin effect generated additional copper loss. These losses can make motor extra heating, low efficiency, output power reduction, such as ordinary three-phase asynchronous motor runs on converter output non-sinusoidal power supply conditions, the temperature rise in general to increased by 10% - 20%.
2, motor insulation strength problem At present middle and small converter, many are using PWM control mode. His carrier frequency about several thousand to rotary union tens of KHZ, this makes motor stator winding to withstand high voltage rate of rise, is equal to the motor applied gradient great impulse voltage, make the motor of turn-to-turn insulation bear more ordeal. In addition, the PWM converter produce rectangle chopped wave surge voltage stack in the motor operating voltage, for motor on insulation pose a threat, ground insulation in high pressure of repeated impact will be accelerated aging.
3, harmonic electromagnetic noise and vibration General asynchronous motor using inverter power supply, will make the electromagnetic, machinery, ventilation, etc factors caused by the vibration and noise has become more complicated. Frequency conversion power contain every time harmonic and motor electromagnetic part of the inherent space harmonic mutual interference, the formation of various sorts of electromagnetic vibration force.
When the electrical magnetic wave frequency and motor the body's inherent vibration frequency consistent or close to, will produce resonance phenomenon, so as to increase the noise. Due to the motor frequency range wide, speed range is big, various electric magnetic wave frequency is hard to avoid motor components of natural vibration frequency.
4, motor to fiber optic rotary joint frequent starting and braking ability to adapt Since using inverter power supply, the motor can be in very low frequency and voltage to no impact on the current way to start, and can use the frequency converter for all kinds of brake way fast brake, to realize frequent starting and braking created conditions, thus motor mechanical system and electromagnetic system in circulation alternating under the action of forces, to mechanical structure and insulation structure bring fatigue and accelerated aging problem. 5, low speed of cooling problems First of all, the impedance of the asynchronous motor are ideal, when the power supply frequency a bottom, high order harmonics power caused by the large loss. Secondly, general asynchronous motor to reduce speed, cooling air volume and speed of three times square ratio decreases, and the motor's low speed cooling conditions deteriorate, temperature rise sharply increased, which makes it difficult to realize constant torque output.