G120 Running at half the requested frequency

Hi,

I have an issue with one of our G120 drives. This happened on installation of a new motor.

I was not present when the motor was installed and the inverter was set up.

We also had an external company look at the issue, and nobody can tell me what exactly they did.

We set the required frequency on the HMI to, for example, 50Hz, the inverter then only runs at 25hz.

Production have been getting around this issue by setting the frequency to 85Hz which will give them 42.5Hz. We cannot go any higher than this so they can never achieve the maximum frequency.

I need to know which parameters affect this. Would this just be caused by an incorrect inverter parameter? Is this something that can be changed on the PLC program?

Some installation details:

CPU 1511-1

TP1200 HMI

Motor: 975rpm  75Kw  137A  

I've checked scaling on p760: 100%.

Adaption speed p1465: 975 rpm

Reference speed p2000: 975 rpm

Any assistance on this is much appreciated.

Thanks,

Tom.

Check inverter settings maybe maximum freq someone changed to 50 Hz (If set new motor maybe someone changed parameters by new motor and this one too) i think you need set to 100Hz maximum freq

Also read this i think you will understand link HERE

Thanks for the reply.

Just to clarify, this motor is rated at 50Hz and we need it to operate at 50Hz (100%).

For us to reach 50Hz currently we would have to set the frequency on the HMI to 100Hz, but the solution I need is for us to be able to set the frequency at the HMI and have the same frequency at the inverter eg. 50Hz set at HMI = 50Hz at inverter.

Yes motor rated motor frequency (P0310) is 50Hz but another parameter is maximum frequency (P1082) it seems set to 50Hz also,but it must be set to 100Hz, example like if PLC give analog signals from 4-20mA  and if in program in PLC is scaled value from 0-100 Hz so then you entered value 50 Hz then PLC give only half value send to inverter only 12mA, but here inverted is set maximum frequency to 50 Hz and then get 12mA it turns to 25 Hz,so my solution rise inverter maximum frequency to 100 Hz andthere must be correct then you enter 50Hz it turns 50 Hz also

Mr.V,

p1082 is showing as Maximum speed (Currently 1000rpm), would setting this to 2000rpm make a difference? I've checked this against 1 of our other lines which has a similar motor and this is set to 2000rpm.

You can try it maybe it helps but i'm comfused why you tell about maximum speed in RPM but parameter show me P1082 in Hz

Also if this not helps try go to parameter P2000 and there set 100Hz

There are some possibilities:

- software problem in the HMI/PLC where the setpoint in Hz is understood as % and sent to the drive like that

- wrong scaling of the setpoint in the PLC/Drive, whether through telegram (4000h = 100%) or analog input (P756-760 for scaling)

I think maybe we are looking at different controllers.

This controller is a G120 CU240E-2 PN where p1082 = Maximum speed.

I can't find maximum frequency anywhere in these parameters.

unknown user

The motor is a 6 pole device rated, after some slip, for 975rpm.

 Correct

unknown user

A 50Hz supply will drive this motor, at full load, at 975 rpm?

 Correct

unknown user

What speed is required for the machine to operate correctly?

The motor is for a dough mixer. We pre-mix at 25Hz, main mix is 50Hz, fruit mix is 15Hz, then the motor kicks the dough out at 15Hz. So at 50Hz we need full speed of 975Rpm, 25Hz should be 487.5Rpm.

unknown user

This motor is a replacement, is it correct for this application?

 The previous motor was 55Kw, this one is 75Kw. All other details remain the same. The inverter is capable of 75Kw. The reason for the upgrade was to increase mix size.

Hope this helps. Forgive me if I've missed anything.