UNI 4401 VFD Problem

[Benyamin]

Hi everybody how are you today?
I have problem with UNI4401 VFD.
Once I turned On 480VAC input power to L1-L2-L3, there is unbalance output voltage on U-V-W instantly, even all feedback wire are unplugged. What is the possibility problem ? I need somebody help me out.
Also could I get complete schematic diagram for this AC Drive?
I am really appreciate to your time and attention.

Best Regard,
Benyamin

[joseph_e2]

Dumb question, but is the input power balanced? Check all 3 phase-phase and phase-neutral. The manual should provide a range of acceptable values. If that's good, then there's probably something wrong with the drive.

I seriously doubt you'll find detailed schematics of the insides of any drive.

[wildbill9669]

With AC drives, the three phase input power is rectified to DC and store in BUS capacitors. The plus and minus of these capacitors feed to six IGBT's which through the circuitry develops a three phase PWM output to the output of the drive. If any of the IGBT's or the driving circuitry is bad, you will get an imbalance on the output. The drive needs to sent in for repair.

[jaden]

I'm not familiar with this particular drive, but is there an Autotune routine available?

[Benyamin]

Hello Joseph_e2,
Yes, three phase input voltage are equal (480V). With solid neutral connected to the right terminal.
There is no schematic diagram inside drive. Anyway I appreciate to the response.
I am still expecting others to help me. Thank you

Benyamin

[Robb B]

There isn't really any reason for a VFD to put different voltages on the wires going to the motor. All the output phases should be equal within the drives specifications (+- a few percent), any other condition is almost certainly a cause for repair or replacement of the drive.

joseph and wildbill both presented this solution earlier.

[Benyamin]

Dear Friends,
Thank you for all responses regarding to my issue.
I agree with Wildbill9669's idea. I will TEST those 6 IGBTs, if there is bad one I will replace it Monday. But the next question is why there is voltage on output side, even there is no any feedback as I mentioned on my first email, also no voltage reference yet.
In other word is why those IGBTs turned on without any reference signal?
Any ideas are wellcome.

Thank you.
Benyamin

[kamenges]

Do you have a motor connected to this drive?

Keith

[Benyamin]

Yes I do

[kamenges]

What level of voltage are you seeing? Single digit volts, tens of volts or hundreds of volts? Is the motor moving at all?

Keith

[Benyamin]

125-90-130

[Benyamin]

The motor was moving but noisy and run internittrn/jogging

[Benyamin]

Sorry wrong typing. It is running intermitten

[Benyamin]

Originally Posted by wildbill9669

With AC drives, the three phase input power is rectified to DC and store in BUS capacitors. The plus and minus of these capacitors feed to six IGBT's which through the circuitry develops a three phase PWM output to the output of the drive. If any of the IGBT's or the driving circuitry is bad, you will get an imbalance on the output. The drive needs to sent in for repair.

Hello Wildbill9669,
I found 1 bad IGBT and replaced it. But the symptom is still same.
I think control board has problem. Would you tell me where are the signals for all IGBTs come from? From controlboard or module placed in the keypad area?
Anybody please response to my issue please.
I appreciate to your attention.

Thank you,
Benyamin