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Danfoss VSD Not Tripping or Protecting The Motor

09/26/2017 5:47 PM

Good day

We are running the conveyor Belt with 22KW, 525V, 30.9A, 4 poles Motor using 22KW 525V VLT Danfoss VSD (FC302). During normal operation, the motor is pulling almost half of its full load (14-15 Amps).

2 motors burnt within 4 days due to over-current/Temperature and the VSD didn't trip.

The motor data was correctly programmed and the Motor Thermal Protection was set on ETR TRIP-1 (Parameter 1-94).

The trip test that i did to Check whether the VSD can trip or not, which i am not sure whether is it the correct method, is that, i changed the motor current settings on the VSD from 30.9A to 10Amps, then i started the Conveyor Belt. during start up, it just flushed current limit on the LCD then keep on running with 14-15 Amps and it didn't trip.

My questions:

1. How do one test the VSD to ensure that it will be able to trip during over current condition?

2. Motor Temperature (parameter 1-9), what is the correct setting on the Motor thermal protection? because there are lots of Trips setting (ETR Trip 1 to 4) and others.

3. what can cause the VSD not to trip during over-current condition? is there any setting that i have missed?

Please assist.

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#1

Re: Danfoss VSD not tripping or protecting the Motor

09/27/2017 2:06 AM

First of, Look at parameter 0-10 to determine which "Set Up" you have active. The drive can be set up for 4 different motors, but only one at a time. So you can select which of the 4 you want to run based on the setting of 0-10. The default is Set Up 1, so ETR-1 is the Electronic Thermal Relay for Set Up 1, ETR-2 is for Set Up 2, etc. etc.

Next thing is that when you set the motor FLC at 10A and the motor draws 14A, that is only 140% of the FLC. In a standard I2t thermal Class 20 overload curve, which that drive says it uses, it will take about 4-5 minutes to trip. How long did you wait?

I think you meant 1-90 for the Overload Protection, not 1-09 (there is no 1-09). You should have that set to match the Set Up that is in 0-10 as I mentioned before. So if you are using Set Up 1, you set 1-90 to a numeric value of 4 for "ETR Trip-1".

Parameter 1-94 is a special setting for ATEX motors, which are required to have a Thermister embedded in them. If you don't have an ATEX (explosion proof) motor, you shouldn't be using 1-94.

This assumes my manual is the same as yours...

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#2
In reply to #1

Re: Danfoss VSD not tripping or protecting the Motor

09/27/2017 2:20 PM

Thanks JRaef, the problem was the "Set Up" mix ups, i hope that i am not going to loose another motor again. But thanks to JRaef

Through my navigation on the parameters, i found out some interesting parameters but I am not sure what must be correct setting on them, Please assist on correct setting on the following: Parameter 4 - 18 Current Limit, present setting 110%;

Par 4 - 17 Torq limit (Generator mode), present setting 100%

Par 4 - 16 Torq limit (Motor mode), present setting 110%

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#3
In reply to #2

Re: Danfoss VSD not tripping or protecting the Motor

09/27/2017 3:10 PM

Current limit: At the setting, in your case 110% of the motor rated current, the drive will respond in a prescribed manner to limit the current, usually by folding back the output frequency in an attempt to shed load, or if ramping, it will cease ramping until the current stabilizes.

Torque limit is similar, Motor Mode just means when it is motoring, Generator mode has to do with if the load is attempting to spin faster than the drive is telling it to, i.e. a downhill conveyor.

There are several other parameters associated with what you might want to happen, and again, drive will react to that based on how you program those actions. if you need to understand it more intimately, I suggest getting Danfoss involved, it's their drive after all.

Are you aware that there is an "Instruction Manual", but that is vague on programming, because there is a separate PROGRAMMING manual. Sounds as though you don't have that.

FC302 programming manual

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