Multilin 369 Relay Trip Signal

[sobeys81]

Hi All,

This is my first post on Motor section and I have already browsed earlier posts to find out if there is an answer available.

I have to protect a 400 HP motor at 600 V with a VFD. The motor has an RTD and Bentley nevada vibration monitor.

This is what i intend to do and seeking an opinion on if I am making some sense.

GE multilin 369 has provision for RTD input. It does not have any input for Vibration monitor so I guess I have to use this interface panel that will interact with VFD for any vibration issue and trip the VFD.

Here is what I have to understand and would appreciate an input:
Link to 369 wiring diagram Page 9/10.

http://www.geindustrial.com/products/brochures/369.pdf

369 relay has quite a few protection features and when I use enervista to enter information about these features what I find is that all of these have a assign relay:

If you see in the wiring diagram on right section : output relay block from 111 to 122. There is trip, alarm and Aux 1 and Aux 2.

I am trying to understand what this means: can I assign all protection features to trip, if I want to trip the VFD ? Can I also assign all the trip action to Aux.1 or Aux.2.

What is the function of Aux. 1 and Aux. 2. I am trying to understand the relevance of these relays.

I would appreciate a word.

 

[dpc]

I would not recommend using a 369 to protect a motor served by a VFD. You should check with GE/Multilin on the suitability of the 369 for this application. GE does say that a 469 can be used, but I am somewhat doubtful about how useful it is.

The output of the VFD looks nothing like the sine wave that the 369 is expecting to see, so how well its internal motor thermal model will work is questionable.

The basic thermal protection of the motor should be provided by the VFD as well as additional protection.

The vibration monitor should provide a dry contact output that can be connected to an input on the VFD and configured to shut down the motor.

Depending on how many RTDs you have, you may need to get a separate RTD monitoring module or run these into a PLC. Some VFDs may have an option for motor RTD inputs. If there is only one, it may be a thermistor and not an RTD.

 

[oldfieldguy]

If you decide to use the Multilin 369, you can add the vibration output contacts as the input to the spare digital input and assign it to the trip relay or one of the auxiliary relays.

You can assign various elements to the output relays as needed.

old field guy

 

[sobeys81]

Thanks dpc and oldfield guy.
Your answers have raised some questions. It could be because of my limited understanding of the subject. I guess that is where you guys come in picture.

dpc:

# 1 .you mentioned that using 369 may not be a good idea. Client wants to use it. 369 is $ 3200 and 469 is $ 7200. So I guess this way 369 has an edge. I guess that is they have this recommendation.

# 2. In my application, I am using a VFD with motor: Itis a ventilation fan application for U/G mine.
How should I decide that which functionality to share between VFD and 369.

"The basic thermal protection of the motor should be provided by the VFD as well as additional protection"
How above statement works: When I have VFD and 369:

whose overload curve kicks in first ?

When we commission VFD; Do we have a selection of an overload curve ?

Do we have a mechanical jam, undercurrent, single phasing and undercurrent protection in standard VFD.

Oldfieldguy:
#1 Is it correct that Basically Trip, Alarm and Aux 1 & Aux 2 are doing the same thing. It is just that they have named it seprately.

Sorry about the length of the question.

 

[dpc]

You need verification from GE and VFD supplier that use of 369 on VFD output will provide necessary motor protection. It doesn't matter how much money is saved if it does not function.

As far as coordination of overload protection, since both are protecting the same motor, it is a bit of a moot point.

 

[sobeys81]

dpc, you have a very valid point and I am going to explore this. One more thing, I got this information from 369 specs. Are the protection below available in VFD:

Phase and residual overcurrent elements (50P/50G)
Unbalance / single phase biasing (46)
Load-loss (undercurrent) (37)
Mechanical jam (48)
Motor stall protection

How does VFD detect a over load ? I would appreciate an input on this ?

 

[davidbeach]

The VFD knows the motor current, and therefore winding heating, far better than any relay between the VFD and the motor ever will. I'm not convinced that there is enough to gain by adding a relay between VFD and motor to justify the cost of the relay. If the VFD at hand doesn't provide sufficient motor protection get a better VFD.

 

[lansford]

In some of our large Medium Voltage applications, Multilin Relays were used between the VFD and motor. Even with the "better" VFDs, we were not able to get the thermal replicating function in the VFDs so we used the Multilin to match the thermal damage curve of the motor.
JIM

 

[LionelHutz]

Most VFD's should be capable of providing the protection you require. Protecting a motor connected to a VFD is different than protecting a motor that is line connected, due to the fact that the VFD is a power conversion device.

The M369 is listed as capable of 20-100hz.