Motors Burning Problem 6

[tlona]

In the past year we have have had (2) 150hp 480V motor windings burn up. The motors are on dedicated circuits and each had a few hundred hours run time prior to burning up. The Motors are started by a VFD which is set up as a soft starter that ramps the motor to full speed in about 15 seconds. The motors drive a vertical 40ft multistage pump used to transfer 2oil between tanks. We have found no mechanicial issues with the pumps. The motors are about 400feet away from the VFDs and I do not believe there are load side reactors installed. The installation replaced existing 200HP motors and removed the 2-stage across the line starters. The existing wiring remained and is about 20years old but successfully meggered and was therefore reused. We have almost the same installation on 4 other motors with no problems. Forensics determined both failures were burnt windings and no problem with bearings. I am going to recommend the installation of line reactors and proper grounding to avoid bearing degradation. I am inquiring to see if there are any other recommendations or experience with this issue. Also curious why the VFD overload did not protect the motor. Thank-you

 

[VicP]

You are getting bad information from Tech support. There is no confusion in the Schneider documents. Any reference to line chokes in the Installation Manual clearly shows the choke installed in the incoming line before the drive and states the choke is required if the available short current is above the value in a table. This is to protect the drive, not the motor. The reference to "Motor Chokes" refers you to the Catalog to select the correct choke. The catalog clearly shows the Motor Choke installed between the drive and the motor.

 

[tlona]

I have the 2014 e-catalog where I did find a recommended dv/dt filter. But I saw no such drawing showing a "motor choke" between the drive and motor. I did see however diagrams for "Line Chokes" Do you have the same catalog and if so which page are you referring too that shows the "Motor Choke". Thank-you

 

[xnuke]

A motor choke is a dv/dt filter and helps prevent overvoltages - perhaps they've simply changed the words they're using.

xnuke
"Live and act within the limit of your knowledge and keep expanding it to the limit of your life." Ayn Rand, Atlas Shrugged.
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[VicP]

The catalog I was referring to is the 2014 ATV61 e-catalog. The diagram showing the motor choke between the drive and motor is on page 1/83.
Here is a link to the catalog
Link

 

[tlona]

Thank-you for that catalog link. That catalogue is very clear compared the Altivar 61 2014 e-catalog I have. Thanx again