G120c cannot reach its setpoint value

Hi,

I'm using two G120c.

Motor Data: Y, 400V, 3.5A, 1.8KW, 60Hz, 1750/min

Max Current (p640[0]): 5.25 A

If one motor starts and runs at 1750 rpm ,has 2.7A, the other motor only manages to reach the set maximum current (5.25A) and then only runs with approx. 18% power. The motor heats up and displays an overtemperature error. This problem is valid for both.

Does anyone have a solution for this or have any idea why this is happening?

Thank You!

Best Regards,

Jey

It's Bitzer CO₂ compressor.

Hati

Are both motors connected correctly? The otherone might be connected as DELTA.

 Thanks for the tip. Both motors are correctly connected as Y and both work perfectly individually. Only when one compressor is running normally does the other have the problem.

jacek d

What are RPMs of the malfunctioning one ? Maybe it is stalled.

The motor can only do up to 315 rpm (18%).

I have 2 hypothesis:

1) it is due to whatever controls the VFDs - it calculates so low speed setpoint that the drive can't handle required torque at this speed;

2) the first drive creates so high pressure, in a piping or a vessel the compressors are connected to, before the second drive starts that the second drive stalls during ramp up.

Hi,

The problem is solved. I increased parameter p640[0].

Thank you all :)