2. If it is to add new load or a new design, you need to estimate the capacity of active power filter. The most important is the estimation of nonlinear load,according to the experience, three-phase rectifier bridge power inverter and UPSas well as the general diode, the total current distortion rate is in commonly 25 ~ 35 (%), special may have about 45%, according to the load rated current value can be calculated from the harmonic current.

      Harmonic current = load current ratings * (25 ~ 35)%
3. If more than one type of load parallel operation, according to the root mean square method to calculate the total harmonic current value.

Total harmonic current value = sqrt

I1---- harmonic current of nonlinear load first

I2---- harmonic current load second nonlinear
In---- harmonic current load nonlinear n station
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