AC Drive tripping motor protection switch heat problem 3

[martinrelayer]

Hello!

we have here one AC drive (ABB ACS800) that has four (4) motor in parallel. The drive is 16amps and the motors are 0,75kw 1amp 690V each.
each output from the drive to the motor has an individual motor protection switch, sized to 1,6Amps
the thing is that te motor protection switch are heating too much today I measure voltage drop and I have 1 volt drop and 1 amp current in each phase.
please see attached pictures.

does anyone have any hint?? is that drive output to four motor in parallel has too much high freq component that causes overheat and problems with bimetallic mechanism??
the cables are 2mm and they are not overheated, also it has a contactor and not overheated, only the motor protection switch!!! I measure ac current rms and I measure 1 amp in each phase for all motors (all motors are the same)

any hint???

 

[waross]

A proposal to start a 15 Hp motor in parallel with four 15 HP moors already up to speed on a VFD?
One of the advantages of a VFD versus DOL starting is is the ability to ramp up the speed.
With an oversized VFD you may be able to do it.
On the other hand the VFD may not like the starting surge even if it is within the nominal capability of the drive.
Please let us know how this works out.


Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[martinrelayer]

looks it arrived here the stuff!
acs800 - 120A - 690V with dU/dT filter (not sine)
15kW motors 690V x 5
application: FAN
5 motors in parallel, each with it's corresponding mot protection switch and contactor.

well I was taking a look at the application, and suggested to remove output motor selection, i mean removing output contactors and not make any logic of it, there's not real need for operation to switch on and off the Fans.

Also, Motor protection switches shall shutdown the drive permanently (for.ex. put a contact in series to external fault digital input of the drive) because I think there's a risk of an electrician to switch on (by hand) the mot protection switch while the drive is in operation, I guess there's an important risk for drive and person. Also if you want to run with four motors, electrical people have to disconnect the motor and jump the Mot.prot. switch contact, I mean they will need to go through the risk inolved and circuit and think about everything.

As for the 1amp motors of the beginning, there will be a modification of the switching on and off the motors, that will include switching off and on the drive before acting on the contactors. I suggested a sine filter but that's ongoing yet.

But let's see how's this beast runs! they need to install everything yet I guess couple of months to the commissioning but I promise to report back how this works
(I won't be involved in the commissioning... ...yet...)

thanks to all,
martin

 

[jraef]

One way I have solved the problem of being able to re-energize one of the motor disconnects while the VFD is in Run mode is to NOT provide users with a handle that goes through the door for those switches. So you still have a Main disconnect that kills power to the entire panel, and THAT disconnect is interlocked with the door. So to reset and re-connect a motor, they must kill all power, open the door, then reset the tripped / off motor disconnect, then close the door and re-start the VFD. While it's true that a "qualified" electrician or someone with authorized access can defeat the door interlock to get inside, you make sure everyone knows that if the VFD blows up, it's on THEM for defeating the purpose of the interlocking, and most likely violating the Arc Flash / Energized Work policy (assuming you have one, which you should).


"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington

 

[controlsdude]

You could also have a motor disable function if its tied to a plc and program same function into the enable signal on the drive. Some drives have there own mini logic that can be used with drive software. The signal could be an hmi function or a switch mounted inside the mcp next to overloads with some procedure mounted on inside of door as a reminder to electricians on how it works. Of course the bypass function would only work when drive is stopped.

And function
bypass on(motorN) + motor protector tripped or turned off(motorN) +next motor = enable to drive
or
bypass off motorN) + motor protector on or turned on motorN) +next motor = enable to drive

 

[Skogsgurra]

I am getting a little bit confused now. Is the '+' operator a Boolean OR (which one would think) or is it a GP 'and' which seems more plausible?

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[controlsdude]

see attached pic worth 1000 words

 

[controlsdude]

I thought this was relevant to the OPs post. Its a webinar that this company puts out.

Simplify Your Application: Control Multiple Motors with One VFD

http://www.rockwellautomation.com/e...6ca5&elqaid=27763&elqat=1&elqCampaignId=13024