3 Phase Variable Speed Motor

Brief Introduction

YVFE5 series 3 phase variable speed motor is controlled by IGBT (insulated gate diode) technology PWM (Pulse width m odulatio n- pulse width modulation) frequency converter. Its power range is about 0.75 ~ 500kW. IGBT technology can provide a very short rise time of the current, the rise time of 20 to 100μs, the generated electrical pulse has a very high switching frequency, up to 20 KHZ. When a rapid rise along the voltage from the frequency converter to the motor end, a reflected voltage wave is generated due to the impedance mismatch between the motor and the cable. This reflected wave returns to the frequency converter and induces another reflected wave due to the impedance mismatch between the cable and the frequency converter to be added to the original voltage wave, resulting in a spike voltage on the voltage wave front. The magnitude of the spike voltage depends on the rise time of the pulse voltage and the length of the cable.

Usually when the length of the wire increases, the overvoltage is generated at both ends of the wire, the overvoltage amplitude at the motor end increases with the increase of the cable length, and tends to saturation, and the overvoltage at the power supply end is smaller than the overvoltage at the motor end, and is almost independent of the cable length. The test shows that the overvoltage occurs at the rising and falling edges of the voltage, and the attenuation oscillation occurs. The attenuation follows the exponential rule, and the oscillation period increases with the length of the cable. There are two kinds of frequency for PWM drive pulse waveform, one is switching frequency. The repetition rate of the peak voltage is proportional to the switching frequency. The other is the basic frequency, which directly controls the speed of the motor. At the beginning of each basic frequency, the pulse polarity changes from positive to negative or from negative to positive, at which point the motor insulation is subjected to a full amplitude voltage that is twice the peak voltage value. In addition, in a three-phase motor with a scattered winding, the polarity of the voltage between the adjacent two turns of different phases may be different, and the jump of the full amplitude voltage may also reach twice the value of a peak voltage. According to the test, the output voltage waveform of the PWM converter, in the 380/480V AC system, the peak voltage value measured at the motor end is 1.2 ~ 1.5kV, and in the 576/600V AC system, the peak voltage value measured reaches 1.6 ~ 1.8kV. It is very obvious that under this full range voltage, surface partial discharge occurs between winding turns. Due to ionization, space charges are generated in the air gap, thus forming an induced electric field that is opposite to the applied electric field. When the polarity of the voltage changes, this reverse electric field is in the same direction as the applied electric field. In this way, a higher electric field is generated, which leads to an increase in the number of partial discharges, eventually causing a breakdown. Tests show that the magnitude of the electrical shock acting on these interturn insulation depends on the specific properties of the wire and the rise time of the PWM drive current. If the rise time is less than 0.1μs, 80% of the potential will be added to the first two turns of the winding, that is, the shorter the rise time, the greater the electrical shock, the shorter the life of the insulation between turns.

Main Technical Parameters

Outline Dimensions

Motor Parameters

Cement

Power Station

Water conservation

Steel

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