Hi All,
Need some thoughts. A customer has come to me about retrofitting a winding machine. Presently, the machine has two 3HP Flex Pak Plus VS Drives (DC). The product has changed somewhat for the original application and no longer has enough HP.

Would you:
a. Leave them DC and raise the HP?
b. Change them to AC?
c. Is it six one way, half a dozen the other?

Thanks,
Kirk S. Hegwood
Hegwood Electric Service, Inc.

 

My vote would be to use an AC drive similar to the ABB DTC line or Control Techniques Unidrive (among other vendors) with sufficient HP. Even if the quality of control was the same between DC and AC (IMHO, these newer AC drives are better here, too), both the motors and drive controllers need to be changed from 3 HP to xx HP (no economic reason to try to reuse anything now existing), and AC motors present much less long term maintenance (worn out brushes, crapped out insulation systems due to carbon contamination,
etc.).

Just happened to be reading an interesting article on AC drives at
http://www.manufacturing.net/magazine/ce/archives/1996/09/issues/na/09a702.htm shortly before reading my email; you may be interested as well.

Bob

 

both ODAWARA and GLOBE have migrated into AC servo drives over the years to control 'flyer' motion on armature winders. I have seen DC steppers used often in 'indexing' an armature to the next slot , readying it for the flyers to do there 'hook-up' on the tang and wind the specified number of turns for that coil. Is it an armature winder we are talking about here in your app. ?

Darren Tichbourne
President, System Integrator, CET
CompuSys Solutions
___________________________________________________________
Email : [email protected]

Website: www.CompuSysSolutions.com

 

Several thoughts come to mind.

1. If you have to make the existing dc motors bigger, can the mechanical configuration of the machine handle the bigger motors? Is there physically enough room for the larger motors? Can the drive train take the extra force or will the line shaft or transmissions snap when you make the motors bigger?

2. Are the existing motors run with field control or strictly armature control? Many times winders are run using field control with low base speed DC motors so that extra turndown capability is available. This presents a big problem sometimes in trying to match up an AC motor solution to an existing DC situation. I have seen cases where a 15 HP DC field controlled
motor works OK but to use AC requires 50 HP motors. Also keep in mind that most DC motor/controller combinations can give you 150% current for a minute or more without seriously damaging the controller or motor. Its not unusual
to need this to start or stop the winding. AC cannot typical give you this so you need to figure it into the size of the motors and drives. You also need to look at whether you require line regen capability. This is fairly
inexpensive with DC but can cost bunches with AC. You will also have to consider whether you need external cooling fans on your ac motors. These can be a real pain as they are typically tacked on with little thought on some AC motor lines. Some don't even have filters on them and can easily become clogged with dust and fail. The blowers supplied with DC motors seem to be
more robust and better thought out.

3. Most of the drive manufacturers (except AB IIRC) have canned solutions available for center winding applications. But, typically these are not well documented and will require fairly extensive factory service to set them up and get them running. Pick a drive manufacturer that has the service readily available close by and has some expereince with such winders. Getting them
to work is not as simple as you might think, at least with the cryptic documentation typically supplied (if any is supplied at all).

 

No. Just a simple soft paper layering process.

Kirk S. Hegwood
Hegwood Electric Service, Inc.

 

I've talked to, as well as have received some email from Autolist - thanks, some people including the ABB rep for this area. Since the customer has replaced the brushes, checked that first, I've about decided to go with an ABB ACS600 with Torque Control. I will increase the HP of the drive to 7 1/2 and use 5 HP motors. This will allow some growth if required. I do
need to double check some regen aspects and probably add a dynamic brake to the system.

Thanks,
Kirk S. Hegwood
Hegwood Electric Service, Inc.

 

Mr. Hegwood,
If your speed range includes very low speeds, less than 100 rpm, and you need good torque at the low speeds, the only reasonable solutions are a closed loop AC vector drive or a closed loop AC or DC brushless servo drive. The direct torque control mentioned in a previous reply will not provide full torque of the motor at or near zero speed. You need DC motor performance. Only closed loop AC drives can deliver equivalent duty.