3 phase SEW motor doesn't always start

reefshark · Aug 23, 2012

Hello

I have a 3 phase motor powered by a ABB compact starter (freq drive) that won't always start (works properly 99/100 times). I see I have the output from the PLC and the AS-i bus output is on when it should be (also swapped the As-i Node to make sure it wasn't bad)

Info
1HP motor

The motor turns a turntable. (mechanically this is fine)

ABB drive is 1.1kw

The drive does not fault out.

When this happens I can see the fan on the motor vibrating (kind of turns back and forth) but not spinning.

I checked the brake it looks good.

Once this happens the process times out after 30 seconds. Once you start it again it works fine.

Has anyone seen something like this before? Any ideas?

L D[AR2P#0.0] · Aug 23, 2012

How is the motor coupled to the turntable ?

Pulleys and belt or gears and teeth

Liam Moran · Aug 23, 2012

You say the motor has a brake.
How is this connected? From the motor terminals or a separate brake control relay?

Liam Moran · Aug 23, 2012

I suspect that the brake is connected to the motor terminals.
The inverter is controlling the voltage level to the motor and
Has has detected a locked rotor on startup. This can be helped by reducing your acceleration time in the drive, but ideally the brake should be controlled by a separate supply controlled by a brake contractor with or without additional wiring for rapid action.

iant · Aug 23, 2012

As Liam has stated - the SEW motors brakes are usually connected to the motor terminals - You will need to change this and seperately exite the brake. Pay attention to the Brake voltage
Check the Motor Connection - Usually expected to be STAR (WHY)

BryanG · Aug 24, 2012

You have a 1HP motor on a 1.1kW drive (1.5HP). Did you enter all the motor data in to the drive so that it knows that the motor is small for the drive.

reefshark · Aug 24, 2012

L D[AR2 said:
How is the motor coupled to the turntable ?

Pulleys and belt or gears and teeth

The shaft of the motor is connected to a sprocket which in turn drive a chain. The chain is attached to the turntable.

Also I can release the brake on the motor and turn the table without any issues.

reefshark · Aug 24, 2012

Liam Moran said:
You say the motor has a brake.
How is this connected? From the motor terminals or a separate brake control relay?

Looking at the drawings I can see there is a separate relay for the brake. To be more specific I take leg 1 and 2 of the 3 phase through a transformer with the output of 230AC, 50VA. The relay is controlled by the an output from AS-i.

Another thing I tried was when the issue happened I manually released the brake to see if that was the issue. The motor still would not begin turning correctly.

reefshark · Aug 24, 2012

BryanG said:
You have a 1HP motor on a 1.1kW drive (1.5HP). Did you enter all the motor data in to the drive so that it knows that the motor is small for the drive.

I did not program the drive. So I don't really know. I will try and investigate that today but I will say we have 2 other completely same setups running without issues (that I know of) I did however in the past pull the parameters from one of the other drives and load into this problematic one.

TomekPLC · Aug 24, 2012

Do you have a choke on the incoming lines?
I've had similar probelm on AB VFD - very seldom it would not produce the torque, after I installed the choke problem went away.
Tom

jrwb4gbm · Aug 24, 2012

Is the motor located near the freq. drive? Some drives are limited to about 200 feet of wire or less from the motor to the freq. drive. Long motor leads can cause strange symptoms.

L D[AR2P#0.0] · Aug 24, 2012

reefshark said:
The shaft of the motor is connected to a sprocket which in turn drive a chain. The chain is attached to the turntable.

Also I can release the brake on the motor and turn the table without any issues.

What torque is required at the motor sprocket to get the turntable moving - can you get a torque wrench on it to check how it compares with the torque you can get from your motor.

iant · Aug 24, 2012

I have had this trouble once before - check all your voltages.
Both sided of the supply C/B and any Contactors.
the description of fault seems to be single phasing - not possible with a VFD but can be seen.
Your brake connection is more than likely not the problem.
Assuming the VFD is a VFD and not a soft starter,(please post the part number), the only way the output can make a motor drive the way you are stating is with either a faulty drive or supply.
Remember VFD function
1- convert AC voltage to a DC Bus
2- Invert DC to an AC output.

Is the Motor Star connected?

robw53 · Aug 24, 2012

do you have a spare drive to swap it out, we had something similar we had a small conveyor that would not run unless you pushed the belt, it would also run the other direction if you pushed it the wrong way, the voltage coming from the drive was unbalanced across the phases.

iant · Aug 24, 2012

hey robw53
their was somthing wrong with that drive or supply.
the output of a VFD will always be the one direction as it is inverted from a DC bus.
The last time I saw an issue like that. the supply contactor had burnt contacts - yellow(White) phase was faulty

3 phase SEW motor doesn't always start

reefshark

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iant

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