The inverter no-load current is greater than the load current

A 75 kw micro can WIN - G9 inverter commissioning the strange phenomenon.Due to the input of the inverter is standard 50 hz sine wave,and the inverter output frequency and waveform permanent magnet motor are differs greatly with the input.Based on the principle of transformer is clip-on ammeter when measuring is dozens of times of the normal (different waveform and harmonic,frequency converter is produced by the thousand Hz level analog sine wave or square wave).If use resistor shunt type current meter measurement,error is not obvious.asynchronous motor As for runtime because of the reduced harmonic component,after feedback current waveform closer to sine wave,so the difference is small,if the series resistor shunt ammeter is basic and calculation results will be very close.(with a current transformer also can produce the same results as the clip-on sheet).Points out that caused by improper use instrument,the measuring error.Also thought that due to the problem of measuring instrument,can lead to inaccurate measurements.


Old electrician,sometimes are under the yoke of experience.But on the frequency converter operation panel display current and clip-on table by measuring current value is similar.The conventional current transformer measurement output current value is not very accurate.As noted.The output of the inverter is ten thousands of square wave voltage.After is connected to the load current is similar to sine wave.But the fundamental wave for the high frequency component.Clip-on ammeter,current transformer,will be used to conventional transformer.Due to the hysteresis effect,unresponsive to the change of high frequency current.Current transformer,the frequency converter of tailor-made,USES hall element to detect the current changes.There is plenty of strain rate.And in the subsequent circuit design has considered the characteristics of high frequency high efficiency electric motor current sampling.So only factory setting accurate,and can reflect the actual size of the current value.If not to pipe the size of the input current,the light output so much of the current,and after loading output current instead of smaller.What's your opinion? Feel free to comment.