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Will this motor work for a 3 phase convertor?

Joined
May 27, 2009
Location
Leland, NC USA
I picked up a 3 phase Baldor motor today at a scrap yard for $30.00 and I thought I dotted all of my "i's" until I read the VOLTS.

Here is what the side plate says:

Cat No- M17
SPEC.- 37BO1Z37
FRAME- 215T
HP- 10
VOLTS- 200
RPM- 1725
HZ- 60
SER.F.- 115
PHASE- 3
CLASS- B
DES- B
CODE- J
NOM. EFF.- 85.5%
P.F.- 76%
RATINGS- 400 AMB-CONT
Weight- 105lbs

The motor only has three wires coming out of it and each have a definite identifier on each one. They are numbered 1,2 and 3.

Sadly the motor seemed to have been pulled originally with care and then they must have decided to scrap it. I still need to take the connector that joined it to the pump shaft (they cut it off with a torch) but I expect to see a complete motor spindle there. The box mounted on the motor was broken off as well.

Here are my questions:

1. Is the 200v going to be a problem? I need to make a 3 phase rotary converter to power a 7.5hp motor on a Grizzly Saw and possibly a future milling machine and metal lathe.

2. I understand that the wires labeled 1,2 and 3 are for each phase or leg but where do you connect the other necessary wires to make the motor run?

3. Does it matter what RPM the future tool will have since this is a 1725 RPM motor? I know the 7.5hp motor is something like 3450 RPM or so.

4. Does a oil filled capacitor rated at 370v work or do they need to be rated at 480v? Can I get by with lower voltages on the capacitor like anything rated 240v and up? Realistically I would think that a rating of 120v and up would work only because each leg (I thought) is coming is as approximately 120v.

My plan was to start with the basics with a Cap on L1-L3 and L2-L3 (L1 and L2 being the workshops 240 Volt Input and L3 being my generated 3rd phase)

Should the motor work okay with my standard home type electricity being rated at 200v?

Is there any special formula to use since the motor is rated at the 200v for the capacitors balance for the final 3 phase output?

I normally use the member name accentphotography as that is part of my business and email but the forum would not allow the "y". Thanks!

Thanks!
 
I did the same thing as you... only I did it twice! I have 2 200V motors (1x 10hp and 1x 20hp). I haven't finished my RPC yet, but based on the reading that I have done here, there are mixed feelings on how well it will work.

One person stated that theirs worked perfect and didn't require any starting caps due to the lower voltage. Someone else stated that with the lower voltage it might actually be more efficient by supplying 240V.

On the opposite side, some have said that the core may become saturated or that the output voltage will be way off and be harder to balance.

If anyone has any other input, I'd be interested to hear it as well.
 
I am not sure about the motor voltage but you might want to send a private message to Peter Hass, peterh5322, and ask this question.

the 370 volt capacitors will work fine

the wires labeled 1, 2, 3 are for the 3 phase power. this is a single voltage motor and you need no more. for a phase converter you have to decide how you are going to start the idler. choices are: capacitor start or pony motor start, either will work on a 10 hp idler
You stated you plan to put single phase power on L1 and L2 and L3 will be the generated leg. Some mfgs use this set up however, the NEC states the generated leg shoudl be L2.

for a cap start, you will need about 900 to 1200 mfd of start caps (electrolytic are OK) and a way to detect when the idler starts plus disconnect the start caps. You can use a time delay relay controlling a 40 amp three pole contactor to do this (distribute the caps evenly among the 3 poles) or you can use a potential relay and a 40 amp three pole contactor. You can also use a manually controlled push button to control the start contactor. The start caps go across the one single phase leg and the generated leg. the largest bank of run caps should also be across this same two legs.

the idler rpm has no effect on load motors. you can use 1150, 1750 or 3450 rpm idlers. the slower ones are quieter.

the Fitch William's plans at the top of this forum are good however his 10 hp is actually a 7.5 hp load capability with a 10 hp idler. you will need to use a 60 amp circuit and upgrade all the components to handle 60 amps if you plan to start a 7.5 hp Asian motor with a RPC.

I would suggest you get the Fitch Williams plans and study them as they are a real good place to start.
I have more detailed plans but it is also a more complicated RPC and may be more than you are ready to tackle.
 
I guess we will just have to wire it and see??? Whats the worst thing that could happen ... fire? My knowledge of 3 phase electricity is very little but I cannot imagine that somewhere there is an abundance of 200v 3 phase power unless there is a big reason for that. Hmmm ... maybe I should contact Baldor and ask them myself. If I get around to this, I will post the answer. By the way ... how many wires do you have on your 10HP 3 Phase 200v motor? Thanks!
 
Toolnut ... great advice. I will go with the L1 and L3 feed and L2 for output. Now about those starting caps ... I never understood this ... are they always hot and constantly plugged into the 240v only to be released momentarily for the startup procedure? If they are hot 24/7 ... do they consume much electricity and should they be disconnected when not in use?

So I get two starting caps that go from a switched hot source to L1 and L2 (output line)? You mentioned the largest bank of run caps should go on the L1 and L2 but L3 will still get run caps as well .. right?

I know this is a vague answer type of question ... but approximately how long would it take to get the idler motor running to shut off the starting caps? I am just asking to get an idea of using a start switch only or going with a timer setup.

Thanks for all of the advice.
 
I do not have a 200 volt motor and have never seen one but they do exist since you have one.

the standard today is a 230 / 460- volt motor. it has nine wires that have to be connected in specified connections for it to run on 230 volt.
for 230 volts
Line 1 connects to T1 and T7
Line 2 connects to T2 and T8
Line 3 connects to T3 and T9
wires T4, T5 and T6 are connected together

For a single voltage motor, you will have only 3 wires, T1, T2 and T3 (maybe labled 1, 2, 3)

You need no starting circuit for real three phase so forget about the starting stuff you see in single phase motors. it does not exist in 3 phase motors.

The problem with using this for a RPC is a motor is designed for no more than 10% voltage variation and your incoming power is likely to be 240 volts. This is more than 10% above the stated voltage on your proposed idler.

I do not know the consequences of using this motor but it will be easier to find a 230/460 volt, 9 wire motor than it will be to build and RPC with this one then learn you do not have the output you really need. Take my first suggestion and ask Peter Haas. If anyone here knows the answer, it will be Peter.
 
Thanks again. I thought it strange that my 5 horse new motor had the lines wired like you mentioned but what was even funnier was that nothing was labeled. Just the pairs lightly twisted together.

I understand that 10% tolerance idea. Since I am running a 220 line volts in to a motor that is made for 200 line volts in, then the L2 leg on the output of the idler would be making 200v and the L1 and L3 from the panel would be 220v.

By the way ... 110v or 120v and 220v or 240v ... I never understood the way people flip flop which voltage they use to describe standard US home panel electricity.
 
By the way ... 110v or 120v and 220v or 240v ... I never understood the way people flip flop which voltage they use to describe standard US home panel electricity.

110,220, are ignorant terms, long obsolete.


BTW a 200 V motor is a standard motor, it's a NEMA standard voltage for a 208 volt supply.
 
most the machine tools i've dealt with are 200 inside now days
on one of the start ups the guy was real picky about tapping the transformer as low as possible to get close to 200 incoming
 
Starting caps are only connected to the idler during the starting phase. If the proper amount is installed the idler should start in about one second and the most 2 seconds. Electrolytic caps are rated for 3 seconds and for about 10 starts per hour. You need about 6 minutes between starts or you could damage the caps.

Have you studied the Fitch Williams plans? do not start tinkering from the brief descriptions we are giving here but rather take these descriptions and try to understand a tried and proven plan. Fitch uses a momentary switch for the start caps so one simply releases the push button when the idler is up to speed. If you use a potential relay you will find this all happens much faster than one can remove his finger from the switch. My RPCs start faster than one can snap their fingers. YOu can do this with one start momentary button equipped with two normally open contacts. One contact is wired to the power contactor coil and one is wired to the start contactor coil. There is no seal in cirucit used on the start contactor so it drops out when the button is released. the power contactor uses a seal in circuit so it stay engergized when the button is released.

Run caps are connected to the idler at all times.

There are several schemes for installing running caps. The Fitch Williams plan uses starting caps on both generated phases. if B is the generated leg, you would have run caps between A & B and between B & C. where B is the same as L2 but I use A, B, C to avoid confusion with the incoming lines from your single phase. the run cap split is about 60% on the primary cap bank and 40% on the secondary cap bank. the start caps go between the same phases as the primary run caps. for instance, if you put the largest run cap bank between A & B then you also put the start caps between A & B/

All caps go before any overload protection for the idler. Some designs do not use overload protection however I use it on all rpcs.
 








 
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