3-Phase Variable Frequency Drive Power Analysis

[@ruanjiayang]

Why can't I acquire PWM voltage waveform as shown here? Al I get is chaotic waveforms, probably due to wave reflection of cables?

[@robert574]

I know this is old now and I've watched it a few times over the years. At 3:53 he says the voltage peak to peak is 700V. Did I hear that right? What causes it?

[@robert574]

I hope someone is still reading this. So, from my reading, I have seen that the output voltage / freq ratio is supposed to remain constant from the VFD (most common ones of a few HP). For instance, driving a 220VAC (RMS), 3ph motor, this ratio is 220 / 60 = 3.667. If I make the calculations on a spreadsheet and graph it, then reduce the frequency in 10% steps from 60 to 6 hz (which should also reduce the speed of the motor by 10%) and keeping the 3.667 ratio constant, the output voltage to the motor drops linearly with the drop in frequency. At 20% of 60hz or 12hz, the voltage to the motor is 44VAC (RMS). If I make the calculation at 1/6 the motor speed (usually stated as the minimum) and frequency of 10hz, the motor voltage is 36.67 VAC. My question: Is this the voltage and frequency relationship that produces a constant output torque of the motor in this range; 10 to 60hz or 288 to 1725 rpm? (for a 1725 rpm motor)

[@tom5778]

Hi Robert, that is correct. You can also maintain the same amount of torque at a higher frequency if you increase the input voltage.

[@imtiazhussain5027]

Hi. I have a dc bus of 800 volts coming from roof top solar panels. This bus is connected to invt vfd to run 3 phase 5HP motor. Can i connect a 3 phase step down transformer and rectifier module in parallel with motor to get clean 30 volt dc to drive a pure sine wave inverter to get 220v ac for home use. Thanks

[@ss-nr6jw]

Wow. Sir please tell me that what will be the output voltage of VFD for 0 to 50 HZ? Is there any formula to find voltage for varies voltage and varies load?

[@niklaswallin9478]

The gui looks really good, but just a tad slow. I guess it's ok though for what it does, we're not playing "doom" on it(i did that on a an oscilloscope once)..

[@dugagjindervishaj3440]

how to measure an Smart drive motor? or how many people call LG Hyper-Drive motor

[@jeophilip4353]

How to make isolated current and voltage measurement

[@KeysightHandsOn]

Jeo philip. The inputs are all isolated. When measuring multiple phases, or an input and output signal you need the isolation.

[@Impedancenetwork]

Wow! That is a bad ass instrument. I wish I had that when I was troubleshooting VFDs. Oh and it is only $22K. Go get you some!

[@KeysightHandsOn]

Thanks.

[@ranjitbindal7633]

sir what is the cost of this power analyser.

[@KeysightHandsOn]

Ranjit Bindal. The PA2201A two-channel model in the US is $16,501 USD

[@mgk2281]

How I guess to find this beautyfull instrument in cheap price in aliexpress

[@edmanid]

thak you for your explaination

[@KeysightHandsOn]

edy aprianto. Thanks.

[@anandvsalunke]

You are triggering on voltage waveform and then saying power factor is really very poor. Are you not supposed to trigger on current waveform that was more closer to sine wave, probably then it could have shown proper power factor

[@humbertocuevas5395]

Hi