overcurrent + dc link overvoltage

Dear experts

What is the significant meaning of having overcurrent + dc link overvoltage alarm and trip at almost the same time?

is it possible to drive sense the overcurrent in regeneration direction?  

Best regards

h_morad

Dear experts

What is the significant meaning of having overcurrent + dc link overvoltage alarm and trip at almost the same time?

is it possible to drive sense the overcurrent in regeneration direction?  

Best regards

One interpretation is that you are converting (braking) mechanical energy back into electric but you have no place to send this electric energy. So the voltage builds up across Mosfets/IGBT (or whatever) and the current same to bring energy back to DC bus (across anti parallel diode with Mosfet).

Do you have braking resistor? Power regenerative module back into electric grid? DC bus connection?

Tanks for reply 

We don't have a break resistor and the application is  ship propeller which work  similar to pump application with s10 induction motor in v/f mode.

here is the trace and as you see we have also large current oscillation .

my question is: 

does the regeneration power is the only possible responsible for this problem or it could be other reason also , because some times drive stop for just over current at about same speed.  

h_morad

Tanks for reply 

We don't have a break resistor and the application is  ship propeller which work  similar to pump application with s10 induction motor in v/f mode.

here is the trace and as you see we have also large current oscillation .

my question is: 

does the regeneration power is the only possible responsible for this problem or it could be other reason also , because some times drive stop for just over current at about same speed.  

I know it might sound silly, but:

• did you verify motor parameter?
• which is maximum dc bus voltage allowed by capacitors?
• did you check any resonance between dc bus capacitors and inductors you may have to smooth current?
• your period of oscillation is 60ms, correct? which means 16 and 2/3rd Hertz. That is 50Hz/3.
• any harmonic trap in the circuit?

You will be running from a generator, which will provide a high impedance supply for the drive system.

Depending upon the available capacity there will be  some harmonic disturbance in the supply, and this system will also be vulnerable to Dc Link over Voltage.

To understand this requires some detail regarding the components installed in the system.

 Tractor

Hi

Thank you all ,for your kind responds.

I think we are closer to understand the problem and attached trace will be very useful.

at the Time of trace the speed is about 650 rpm and so the period about  45 ms.

could you tell this is harmonic or regenerating problem or any other suggestion?

for your information there is no harmonic filter before or after drive at the time.

motor is 1050 kw,630V,1160 A, induction running by 1250A S120 drive

thanks a lot. 

The trace is not clear enough to make a judgement, a harmonic analysis will provide the right diagnosis, without a clear assessment we would be guessing.

Can you confirm the supply transformer data: fault level, impedance, primary & secondary Voltage (690V), and kVA rating.

Thinking ahead:

An input reactor could be considered, but will be a massive lump to find a home for.

An active filter could be considered, but costly.

First however you need some proper measurements.

Tractor