Daisy chaining 1 hp motors

Status
Not open for further replies.
L

lilsparky

Member
Location
Madison, Al
Good Friday everybody,
We are upgrading a facility where we are replacing hydraulic motors with electric motors on specific pieces of equipment. This particular piece of equipment moves on a rail we call translation movement and also rotates we call rotation movement. There will be a motor for each movement mounted on a "dolly" and there are 10 dollies. These dollies are tied together to move together for translation and rotation. We are thinking about daisy chaining these motors. The translation motors will be VFDs and the rotation will be servos.

Here's my question, does it meet code to daisy chain the motors? For example..feed dolly 10 from one main VFD controller, then feed dolly 9 from dolly 10, then dolly 8 from dolly 9 and so on? Is it possible to just provide one size for the cable? I couldn't find anywhere in the NEC where this would be a violation. do I just ask a wire mfg for cable make plugs on both ends of the cable?

Thanks as always!!
 
lilsparky said:
Good Friday everybody,
We are upgrading a facility where we are replacing hydraulic motors with electric motors on specific pieces of equipment. This particular piece of equipment moves on a rail we call translation movement and also rotates we call rotation movement. There will be a motor for each movement mounted on a "dolly" and there are 10 dollies. These dollies are tied together to move together for translation and rotation. We are thinking about daisy chaining these motors. The translation motors will be VFDs and the rotation will be servos.

Here's my question, does it meet code to daisy chain the motors? For example..feed dolly 10 from one main VFD controller, then feed dolly 9 from dolly 10, then dolly 8 from dolly 9 and so on? Is it possible to just provide one size for the cable? I couldn't find anywhere in the NEC where this would be a violation. do I just ask a wire mfg for cable make plugs on both ends of the cable?

Thanks as always!!
Click to expand...

You could supply 10 motors from one VFD however.

Each motor would need it's own motor overload device

The motors would not necessarily turn the same speed as the mechanical load / electrical characteristics will be different for each motor.
 
I understand that I can control 10 motors with one VFD but can they be daisy chain in a master-slave type of way. For example, let dolly 10 be the master and then let motors 9-1 be slaves. So I bring in one feed to dolly 10 and then jumper the motor feeds from 10 to 9 to 8 etc. if this is making any sense. I'm trying to minimize the about of cables in the trench. My space allocation makes it hard to feed each motor with a separate feed.

Can you explain more about having their own OL device? will that go on the motor?
 
I would never do it, because the VFD provides far superior overload protection than a thermal overload device at the motor...which is going to be more applicable for a motor at full speed.

Would all of your wheels be turning at the same speed, or do you need to reduce the speed of the inner wheels when turning? I'd think for precise steady and controlled movements individual VFDs would be best. 1HP isn't big either. Each dolly could then contain its own VFD, be standalone, and then you could daisy chain the feed and control.
 
As someone else said, you can do this but each motor has to have its own overload protection.

There are various ways this could be handled. One of the easiest would be to put an IEC overload at each motor. That way you could bring one set of three power wires out that would daisy chain to each OL. You would need to wire all the OL contacts in series and tie it back to the enable of the drive to shut off the drive if a motor goes into overload.
 
lilsparky said:
I understand that I can control 10 motors with one VFD but can they be daisy chain in a master-slave type of way. For example, let dolly 10 be the master and then let motors 9-1 be slaves. So I bring in one feed to dolly 10 and then jumper the motor feeds from 10 to 9 to 8 etc. if this is making any sense. I'm trying to minimize the about of cables in the trench. My space allocation makes it hard to feed each motor with a separate feed.
Click to expand...

Yes, code wise you could probably do it. If it is practical is another issue to determine.

Can you explain more about having their own OL device? will that go on the motor?
Click to expand...

The code requires each motor have individual overload protection, in your design you would have to locate an overload device at each dolly for that dollies motor.

There are different kinds of OL devices that could be used. I would assume in your design you would want all motors to stop if one motor goes out on overload, to accomplish this you could run another set of conductors daisy chained to each dolly for a stop circuit controlled by each motor overload.

I am sure others will have more suggestions, there are always many ways to get it done. :)
 
Hmmm, this is a lot to think about. Yes all the wheels will be turning at the same time. The translation movement is real slow so not concern about a wheel slippage. Now have to make the decision on whether to use VFD as OL device then daisy chain or put OL device on each motor then daisy chain.

Hmmm so much to think about. Thanks!!
 
Status
Not open for further replies.
Top