powering 3 motors using 3 VFDs through a single CB - Electrician Talk - Professional Electrical Contractors Forum
CLICK HERE AND JOIN OUR COMMUNITY TODAY, IT'S FREE!
Go Back   Electrician Talk - Professional Electrical Contractors Forum > Electrical Trade Topics > PLCs, VFDs, Motors and Controls


Like Tree16Likes
  • 2 Post By pudge565
  • 1 Post By gpop
  • 1 Post By frenchelectrican
  • 1 Post By tates1882
  • 1 Post By gpop
  • 5 Post By gpop
  • 5 Post By JRaef
Reply
 
Thread Tools Display Modes
Old 07-03-2019, 12:36 PM   #1
Junior Member
 
Join Date: May 2019
Location: Calgary, AB
Posts: 16
Rewards Points: 34
Default powering 3 motors using 3 VFDs through a single CB

We have 3 2HP motors that need to be synchronized with motion and position. We have installed 3 VFDs that can handle motion and positioning, but the power conductors are protected with a single 3-pole CB and then the power conductors are daisy chained on the VFD inputs.

Is that a safe practice or does each set of conductors (3 wire) going to the VFD need their own 3-pole CB? We need the whole circuit to shut off if one motor pulls too much current. Also we are installing overloads for each motor, but right now I just want to know if a single CB is enough for the whole circuit.

FLA for each motor is about 7A, so we are using a 30A CB (240VAC).
Zylonite is offline   Reply With Quote
Join Contractor Talk

Join the #1 Electrician Forum Today - It's Totally Free!

ElectricianTalk.com - Are you a Professional Electrical Contractor? If so we invite you to join our community and see what it has to offer. Our site is specifically designed for you and it's the leading place for electricians to meet online. No homeowners asking DIY questions. Just fellow tradesmen who enjoy talking about their business, their trade, and anything else that comes up. No matter what your specialty is you'll find that ElectricianTalk.com is a great community to join. Best of all it's totally free!

Join ElectricianTalk.com - Click Here JOIN FOR FREE


Warning: The topics covered on this site include activities in which there exists the potential for serious injury or death. ElectricianTalk.com DOES NOT guarantee the accuracy or completeness of any information contained on this site. Always use proper safety precaution and reference reliable outside sources before attempting any construction or remodeling task!

Sponsored Links
Advertisement
 
Old 07-03-2019, 03:06 PM   #2
Senior Member
 
Join Date: Jan 2011
Location: canada
Posts: 1,448
Rewards Points: 2,010
Default

check manual of the vfd they will tell you what size breaker or fuse to use, secondly, no overloads on the output of a vfd (only time they are needed is when more than one motor is connected to one vfd)
vfd should not be stopped by removing power (unless it is an emergency), just use the stop function on them for stopping, for e-stop you can use a contactor on the line side of vfd

Last edited by oliquir; 07-03-2019 at 03:08 PM.
oliquir is offline   Reply With Quote
Old 07-03-2019, 03:42 PM   #3
Certified Organic A-Hole
 
pudge565's Avatar
 
Join Date: Dec 2007
Location: PA
Posts: 1,693
Rewards Points: 1,022
Default

Quote:
Originally Posted by Zylonite View Post
We have 3 2HP motors that need to be synchronized with motion and position. We have installed 3 VFDs that can handle motion and positioning, but the power conductors are protected with a single 3-pole CB and then the power conductors are daisy chained on the VFD inputs.

Is that a safe practice or does each set of conductors (3 wire) going to the VFD need their own 3-pole CB? We need the whole circuit to shut off if one motor pulls too much current. Also we are installing overloads for each motor, but right now I just want to know if a single CB is enough for the whole circuit.

FLA for each motor is about 7A, so we are using a 30A CB (240VAC).
The breaker should never open on a motor overload as it is there for ground fault and short circuit protection only in a typical motor install. The overload protection is taken care of via the VFD.

You would use an enable circuit for what you are trying to do. You run that enable circuit through NO contacts on each VFD and set that contact to close when the OL is not tripped.

No offense, but from this and other posts you made it sounds like you are in over your head and should be hiring a controls company to set this system up for you, they will have the experience necessary to make this happen with no damage to equipment or personnel.
glen1971 and gpop like this.
pudge565 is offline   Reply With Quote
Sponsored Links
Advertisement
 
Old 07-03-2019, 07:13 PM   #4
Senior Member
 
Join Date: May 2018
Location: florida
Posts: 1,505
Rewards Points: 1,230
Default

As pudge and other have said you are in over your head. If a drive shuts down due to one of a hundred different problems the others need to stop.

As for the breaker that's fine as long as you have fuses that are rated to the manufacturers specs between the breaker and drives (and the wire is correctly sized)
pudge565 likes this.
gpop is online now   Reply With Quote
Old 07-03-2019, 09:58 PM   #5
Modérateur
 
frenchelectrican's Avatar
 
Join Date: Mar 2007
Location: Philippines
Posts: 8,635
Rewards Points: 16,782
Default

Quote:
Originally Posted by Zylonite View Post
We have 3 2HP motors that need to be synchronized with motion and position. We have installed 3 VFDs that can handle motion and positioning, but the power conductors are protected with a single 3-pole CB and then the power conductors are daisy chained on the VFD inputs.

Is that a safe practice or does each set of conductors (3 wire) going to the VFD need their own 3-pole CB? We need the whole circuit to shut off if one motor pulls too much current. Also we are installing overloads for each motor, but right now I just want to know if a single CB is enough for the whole circuit.

FLA for each motor is about 7A, so we are using a 30A CB (240VAC).
Do not install the overload blocks at all due the VSD will take care of it.

I think you should back this out a little and let someone more experiniced one to deal with this set up so you can watch as you learn along the way.

you will need a comm cable to tie all three VSD so they can work as one unit. and any fault show up it will shut down all of it. again have someone who is well verised with this set up.
pudge565 likes this.
__________________
Bleu est beau.
frenchelectrican is offline   Reply With Quote
Old 07-03-2019, 10:58 PM   #6
zap
 
tates1882's Avatar
 
Join Date: Sep 2010
Location: northwest
Posts: 1,299
Rewards Points: 1,040
Default

Personally I would have ran the three motors under one Vfd with separate OLs for each motor.
micromind likes this.
tates1882 is online now   Reply With Quote
Old 07-04-2019, 12:10 PM   #7
Junior Member
 
Join Date: May 2019
Location: Calgary, AB
Posts: 16
Rewards Points: 34
Default

Quote:
Originally Posted by tates1882 View Post
Personally I would have ran the three motors under one Vfd with separate OLs for each motor.
The motors need to be sync'ed and the PLC needs feedback control from each motor. So it's impossible to run it through a single VFD.
Zylonite is offline   Reply With Quote
Old 07-04-2019, 12:16 PM   #8
Senior Member
 
Join Date: May 2018
Location: florida
Posts: 1,505
Rewards Points: 1,230
Default

Quote:
Originally Posted by Zylonite View Post
The motors need to be sync'ed and the PLC needs feedback control from each motor. So it's impossible to run it through a single VFD.
Now we are starting to get some of the details that should have been in the original post.

So we now have a plc and feedback from the equipment

still put a bet that most of us controls guys could do it with one vfd and 3 starters if we were ever challenged to do it.
micromind likes this.

Last edited by gpop; 07-04-2019 at 12:19 PM.
gpop is online now   Reply With Quote
Old 07-04-2019, 12:19 PM   #9
Junior Member
 
Join Date: May 2019
Location: Calgary, AB
Posts: 16
Rewards Points: 34
Default

Quote:
Originally Posted by gpop View Post
Now we are starting to get some of the details that should have been in the original post.

So we now have a plc and feedback from the equipment
yes we have a PLC and encoders.
Zylonite is offline   Reply With Quote
Old 07-04-2019, 12:38 PM   #10
Senior Member
 
Join Date: May 2018
Location: florida
Posts: 1,505
Rewards Points: 1,230
Default

Quote:
Originally Posted by Zylonite View Post
yes we have a PLC and encoders.
So keep it simple.

Breaker 30 amp. #10 wire to 3 finger safe fuse blocks.
fuses sized by drive manufacture
#12 wire from fuses to drive

1 e-stop field mounted button to e-stop relay.
drive enable inputs via e-stop relay

plc input from each drive (hardwired or network)
run signal (not a at speed signal)
fault signal
inputs from encoders
maybe 3 home switch's depending on the encoders

plc outputs (hardwired or network)
run signal
forward/reverse signal
Analog for speed control.

Programming requires someone with a good understanding of pid loops

Add buttons, switches or a hmi
gpop is online now   Reply With Quote
Old 07-04-2019, 01:03 PM   #11
Modérateur
 
frenchelectrican's Avatar
 
Join Date: Mar 2007
Location: Philippines
Posts: 8,635
Rewards Points: 16,782
Default

Quote:
Originally Posted by Zylonite View Post
yes we have a PLC and encoders.
Ahh that clear up that part.,,

Follow Gpop listing above me that is pretty much clear cut on that set up.

Just prepare to get some nonstandard parts but basically you should able deal with this pretty good once you understand the set up.
__________________
Bleu est beau.
frenchelectrican is offline   Reply With Quote
Old 07-08-2019, 04:50 PM   #12
Senior Member
 
JRaef's Avatar
 
Join Date: Mar 2009
Location: SF Bay Area, California
Posts: 5,111
Rewards Points: 2,106
Default

The breaker protects the conductors feeding the VFDs, so if you have sized the conductors appropriately, there is no problem. The VFD manual will list the MAXIMUM size OCPD (breaker or fuse) that the drive can have upstream. Anything that size or smaller is fine. Take note however, a lot of small VFDs like this are NOT going to be listed to be used behind breakers at all, they might require fuses. RTFM.

The VFDs are required to protect the motors, not the breaker. If it is a UL / cUL listed drive, each VFD will have both the Short Circuit and Overload Protection built into it that is programmed based on the motor data that you enter; that became a requirement for listing in 2005.

If you are using some kind of cheap no-name Asian drive bought off of a website, you are playing with fire anyway and all bets are off as to what protections they do or don't provide.
__________________
"If you don't know where you're going, then any direction will do." -- Lewis Carroll
JRaef is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -4. The time now is 12:35 AM.


Powered by vBulletin® Version 3.8.8
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.1
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
User Alert System provided by Advanced User Tagging (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Our Pro Sites Network
ContractorTalk.com | DrywallTalk.com | HVACSite.com | PaintTalk.com | PlumbingZone.com | RoofingTalk.com