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The 1 converter capacity and rectifier phase relationship


The frequency converter with input 6kV power system must be consistent with the provisions related to inhibition of harmonic state. This and the power capacity and the device rated power. Short circuit capacity within 1000MVA, 1000kW device 12 (secondary side of the transformer can be double winding), if the 24 phase power is up to 2000kW, 12 phase basically eliminated the 5 and 7 harmonics in bigger amplitude. Rectifier phase number more than 36 phase, harmonic current amplitude reduced significantly, and the manufacturing cost is too high. If the short circuit capacity of the power grid 2000MVA, the device allows greater capacity.


2 select high voltage defects


Selection of voltage level is too high due to the high investment, long payback period. The increase of voltage grade, the insulation must improve the motor, the motor price increase. The increase of voltage grade, the power semiconductor devices in inverter series number increase, rising costs. Visible, for 200 ~ 2000kW motor system by 6kV, 10kV voltage grade is not economic, not very reasonable.


3 the highest voltage below 3kV can save a lot of investment


Considering the necessity of voltage level from the characteristics of electronic devices and safety coefficient of power, the power electronic device voltage and motor allows the dv/dt limit, 6kV converter must use the multi level or device series, cause line complex, expensive, poor reliability. For the 6kV inverter for 1700VIGBT, to American Luo Binkang PERFECTHARMONY series 6kV high voltage frequency converter as an example, each phase consists of 5 rated power unit 690V series, a total of 60 devices of three-phase. If using 3300V devices, also need 3 series a total of 30 devices, a huge number of. On the other hand device with small current, device current capacity is not fully utilized, taking 560kW as an example, 6kV motor current is only about 60A, while the IGBT 1700V current has reached 2400A, 3300V device current up to 1600A, a large device can not be used, must use a large number of small devices in series, unreasonable. Even if the motor power is 2000kW, the current is only about 140A, is still very small.


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