VFD Motor Overspeed 1

[TugboatEng]

I am having an issue with a winch motor operated by VFD. During powered inhaul the motor is tripping on overspeed. The max frequency and overspeed trips are set correctly. I don't see how it's possible for the VFD to drive the motor at excessive speed. Is it possible for the shaft encoder to output a faulty speed signal that is high?

 

[waross]

Can you check the speed independently of the shaft encoder?
Is this a new installation or a problem that has developed over time in service?

Bill
--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[TugboatEng]

It's not clear when the problem began. The crew has been working around it.

To get the motor speed? Now you're asking the hard questions. I guess I could pull the rotary coupling for the clutch and put a nipple to extend it so I can use an optical tach. I don't get access to the boat very often for troubleshooting.

To make the problem worse, the Drive Explorer file in the HMI is corrupt and I didn't bring my laptop.

 

[edison123]

If you have a stroboscope, you can check the speed and actually see the rotor stationary at its speed. It's what I do when I don't have access to put a tach.

Muthu

http://www.edison.co.in

 

[TugboatEng]

This is a TENV motor driving an epicyclic gear turning a sprocket in an enclosed chaincaee.

 

[edison123]

Doesn't it have a fan at the back end?

Muthu

http://www.edison.co.in

 

[edison123]

TENV. Bummer. Any key projection at the back of the coupling?

Muthu

http://www.edison.co.in

 

[TugboatEng]

The winches with captains have shaft brakes so I can pull the brake housing cover to expose the shaft. No capstain on this one. This winch has a rotary coupling for the pneumatic clutch. I think that's my only access though that may be after the clutch.

I'm in contact with the vendor and they have me chasing limit switches that indicate the park position of the control levers but I feel the VFD shouldn't be capable of driving a motor in to an overspeed condition?

 

[edison123]

If you can put a paint mark in any of the motor rotating part before the clutch, a strobe could work. I say strobe because you can actually see if the rotating component is swinging around the base speed.

Muthu

http://www.edison.co.in

 

[jraef]

Noise on the encoder cable will cause this. Make sure the connections are good and the shields are all intect and connected properly.


" We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden

 

[edison123]

Will the clutch slipping mess up the encoder?

Muthu

http://www.edison.co.in

 

[TugboatEng]

The encoder is directly mounted to motor shaft, no clutch involved.

Ahah! Got to the boat today. There is a cover on the encoder end. Now if I only had a tach.

 

[waross]

Are they pulling line out with engine power? (Come in close to attach the tow line and then motor away to pull slack.)
They may indeed be running the motor over-speed.
But;
If the over-speed is NOT accompanied by over current, then suspect an issue with the encoder system.

Bill
--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[TugboatEng]

The overspeed is being driven entirely by the motor. Motor is pulling in a slack line when it overspeed trips. Current is low because load is low.

I need to add, this is in render/recover mode which is intended to maintain a constant tension on the line. The trip only occurs in the in-haul.

 

[waross]

Your drive may be configured to maintain too much tension.
If the drive is increasing speed trying to maintain a preset tension, that may drive the motor over-speed.
It is probably worthwhile to look at that parameter.

Bill
--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[TugboatEng]

It does it even in minimum tension. The drive is also capped at 100hz, 2000 rpm. Overspeed is set for 3000 rpm.

 

[RedSnake]

What kind of encoder is it ?
A tachometer generator or a impulse encoder ?
With a tachometer generator it would always give a lower value if broken.
With a impulse encoder it could give a higher value if broken but not lightly 1,5 times as much.
Then it would be more reasonably that it is set up wrong in the VFD.
Wrong code gray vs binary or the wrong amount of bits with or without sign or something like that.

Best Regards A

“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

 

[TugboatEng]

The encoder is here:

https://ecatalog.dynapar.com/ecatalog/incremental-encoders/en/RIM_1250_NexGen

It's an incremental type, magnetic.

 

[TugboatEng]

Ahh, you guys/gal were right. It does appear to be a settings issue. Overspeed setpoint is only 10 rpm different from max speed and after only 2ms duration. I finally figured out how to get in to the parameters list. There is a handy little HMI on the drive itself.

 

[RedSnake]

And do you have the exact ordering code ?

/A

“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein