help with a motor controller

insanity

insanity

Joined
Feb 28, 2002
Messages
392
Here is my situation. I'm thinking of upgrading my poor underpowered motor. I have a 15hp 3 phaze motor lying around. My question is would it be cheaper to buy a 2hp motor + controller or just a controller for the 15hp I already have. I've read enough to know that controllers need to be matched to the motor, but not how. Help?

Thanks
 
Wayne, it'd be cheaper to buy a new 2 h.p. motor and controller for sure...one for your 15 h.p. motor will set you back at least $900.

:)

-Darren
 
You can get a VFD for around $100-150 on surplus center (for 220V).

If you need to run it on 110V, get a step-up transformer for another $100.
 
Hi Dan, the only VFD I saw on surplus center was one for 460VAC....good price, but only 1 h.p. and way high voltage! :)

:)

-Darren
 
15 HP :eek: you must have some stock in the hydro company :D

if you have two or three of the 3 phase motors you can make your own
converter,, you just have to start the mess up with a reg smaller motor
(110, 220, AC or DC what ever,it's just to start the 3 phase motor..)

the more 3 Phase motors you have in-line the more true a 3 phase you'll have out the last one.
that's all a rotary converter is.. ;)
the first motors are used to convert and don't use much ele, :)
 
It was in a catalog....I'll look it up if you're interested, Wayne.
 
Hello Wayne

If you want to use the 15hp motor, you will probably have to get a controller (VFD, VSD) that is rated for much more than 2hp. Otherwise, the motor might not start or you could be tripping out your drive on start up all the time.

Only part of the current fed to the motor provides the energy to actually turn the motor and do the work. The remainder, the magnetizing current, maintains the magnetic fields in the motor and is fairly constant, for each motor. When a big motor is connected to a controller with a much lower rating, a large fraction of the controller's output capacity is used up supplying the magnetizing current so less is available to actually turn the motor.

Get a controller that will allow you to ramp up the speed of the motor gradually, when you start it. This will reduce the peak current and reduce chances of tripping the controller or your main circuit breaker. A rule of thumb we used at work when designing the controllers is that the starting surge current drawn by a motor WITH NO LOAD can be up to 6-8 times the rated current of the motor if there is no mechanism to limit the current. Most of you will be running from a residential supply, not an industrial supply with much higher current capabilities. Come to think about it, the inrush current for a 15hp rated controller may trip the breaker in your house so you won't get far down that road.

Contact me directly if you want me to ask the applications engineers here at work about matching the controllers to the motor. My experience with the controllers is mainly on the detailed design of the internal circuitry.

Phil
 
First thanks for the replys. Second I suppose I should have included some more specifics in my original post. So here they are. The shop I work from is an old industrial building. I have access to way more 3 phaze power than 110. I think I would have to create a 220 line if I needed one. I dpn't pay the electric bill so amperage draw isn't a problem. The 15hp motor is from an air compressor that used to be in service in this building. I don't really think I need anything that big (I'm sure a 10hp would do just fine :p) it's just what I happen to have accesss to for free. What whould be your recomendations for getting a variable speed setup for my KMG as cheaply as I can that will not bog down, ever, even when running slow. Ok so maybe it could bod down sometimes. My only expirience with variable speed has been the machines at the shcool in old washington and they had no torque at all and I found that way more annoying than a slightly underpowered step pully setup. Save me from my stupid ideas. (I know I'll hook up my grinder to my friends v10 ford. that should do the trick.)
 
Wayne with that situation
why not use the one motor
on a few grinders( maybe 4-5 :D ) and step them all at what ever speed you want

I sure wish I was in a free ele. situation with a 15 hp motor :eek:
I'd love to have 5-6 grinders set up. I just wouln't want to get caught up in that baby.. :eek: :)
 
I mistook your first post, Wayne. I was giving you the benefit of the doubt spelling-wise....thought you meant to put 1.5 HP (vs. a new 2HP).

I'd keep the motor - use it for something else.

Get a nice 3HP motor and controller - you won't ever bog it down.
 
Hello Wayne

With a three-phase motor matched to a modern controller, you should get full rated torque from zero rpm all the way up to rated rpm. Therefore, you should not bog down at slow speed unless the hp rating of the motor was too low to begin with.

If you are in an industrial building, you may find that you have 480V available. If so, this will increase the number of controllers that you can use. Only some makes/models will run on three-phase 220V. Even fewer will run on single-phase 220V. Three-phase motors can often be configured to run from different voltages by changing some connections, so check before you buy. Make sure that the wiring and THREE-PHASE circuit breakers that you use are rated for the voltage that you are using.

Do not cheap out too much on the controller for safety's sake. Some of the really low priced ones do not come mounted in a box. There is a lot of electrical energy stored in the controller and that energy can do a lot of damage (I've blown up a few in my work). Call around to the various controller manufacturers and/or their distributors. Some may sell you reconditioned units quite cheaply (I think that Toshiba sells theirs for about $200). You can probably get a better quality controller, with a warranty, than buying a new, bargain basement make/model.

Do mount the controller where there is plenty of clean, cool air available. Very few of the controllers are dust-proof. They will not tolerate getting conductive dust, like from your grinder, blown/sucked into them and can fail quite dramatically. You should be able to mount the speed control potentiometer or display module, if it is a more sophisticated one, close to your grinder with the controller farther away in a clean area.

You should be able run several motors with the same controller. It is possible to just connect them in parallel as long as the total ratings for the motors is within the rating of the controller. Alternatively, add a three-phase circuit breaker in series with each motor so that only one is connected at a time (this is probably safer). Three-phase motors are relatively cheap compared to the controllers.

Good luck.

Phil
 
PSO: is there a way I could check or tell what the voltage rating for a circuit is? Nothing is labeled, so it would be from the breakers or something like that.
 
Hello Wayne

Make sure that what you are doing is safe by getting the help of an experienced professionalelectrician who can spend some time looking at the electrical system in this building. Don't just rely on the advice of a buddy who is handy or did an electronics course sometime ago. People do all kinds of wierd and funky things with electrical systems. They get modified so that the drawings are no longer representative any more. The building maintenance guy, if there is one, would be a good place to start.

Phil
 
Can anyone use a 3HP single phase 220v motor ?? It's yours if you pick it up .
 
mete said:
Can anyone use a 3HP single phase 220v motor ?? It's yours if you pick it up .
Click to expand...

Mete
do you know what it weighs for shipping or do you mean pick it up personly
at your place?? :(
 
Dan smells a deal!!!!!
Car3.gif
 
It weighs a lot ! I have lifted it reluctantly, maybe 2 sacks of concrete ?? ( not very scientific !) I know nothing about shipping costs.It's a long drive for you ( I'm at the NY-NJ-PA intersection) maybe you could find someone driving to NE ?
 
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