10 hp idler 220/440 tips please

I procured a nice 10hp 3ph 220/440 I'd like to use as an idler for my small shop. It is way more motor than I need for providing 3ph however I've read that one this large would allow me to forgo the use of the capacitor type RPC. Can anyone help me-w-ideas on the setup for this please. Also are motors wound-w-a standard (nema?). This is made by ThermoKing in Minn and there is no wiring diagram.
Thanks
Howard Christian
Wilmington, NC

Howard,

Can you give us more information about the motor.

How many leads does it have and how are they numbered?
What is the RPM
What is the voltage rating (is it dual 230 volt / 460 volt)?
What are the FLA amps?

A photo of the nameplae will be a big help also. Most USA made motors will have leads numbered per the NEMA standards and we can look up connection diagrams and based on the number of leads and the numbering scheme. We can most likely pick the correct connection diagram from this information. Some of the questions above will not affect the connection scheme but provide information to help you with the RPC idea.

You can use an idler with no run capacitors as long as it is at least 2 times larger than any load motor. You will have low voltage on the generated phases but it may be acceptable to you. You will need a method of starting the idler and you have some choices:

kick start with your foot
rope start it like a lawn mower
use a single phase motor as a "pony motor" to start it
use start capacitors and either a time delay relay or a potential relay to control a contactor which will switch the start capacitors in and out.

You seem to have some phobia about capacitors however they are the best way to start the idler but you do need to do some wiring. The capacitor start designs will start and disconnect the start capacitors when the idler is up to speed.

"You will have low voltage on the generated phases..."

For that ratio of idler to load motor size, probably they
will all be within ten percent.

SWAG.

Jim

toolnut said:

Howard,

Can you give us more information about the motor.

How many leads does it have and how are they numbered?
Not certain but I will get back-w-this. It was manufactured by Thermo King Corp. I called them but got hassled and no help?
What is the RPM. The RPM is 1725 if run at 60hz
What is the voltage rating (is it dual 230 volt / 460 volt)? Yes it is dual voltage
What are the FLA amps? Full Load Amps=85
It has 2 very similar nameplates-one for 60hz and one for 50hz

A photo of the nameplae will be a big help also. Most USA made motors will have leads numbered per the NEMA standards and we can look up connection diagrams and based on the number of leads and the numbering scheme. We can most likely pick the correct connection diagram from this information. Some of the questions above will not affect the connection scheme but provide information to help you with the RPC idea.

You can use an idler with no run capacitors as long as it is at least 2 times larger than any load motor. You will have low voltage on the generated phases but it may be acceptable to you. You will need a method of starting the idler and you have some choices:

kick start with your foot
rope start it like a lawn mower
use a single phase motor as a "pony motor" to start it
use start capacitors and either a time delay relay or a potential relay to control a contactor which will switch the start capacitors in and out.

You seem to have some phobia about capacitors however they are the best way to start the idler but you do need to do some wiring. The capacitor start designs will start and disconnect the start capacitors when the idler is up to speed.

Click to expand...

I suppose I came across as overly cautious but actuallyI have no phobias other than most non-military federal government agencies. I admit to being ignorant and wish to get educated so I can get this RPC up & running but another wrench in the mix is a lack of local suppliers. One interesting possible find I came across is several "ballast kits" that are surplus items and were spares for some HID lighting. They each consist of a multi-tap transformer and a capacitor and I am thinking I can use these to balance the legs but I need to get more info on these repair kits. I know one local guy that uses transformers in his RPC obviously-w-capacitors as well. He warned my that I might have trouble-w-current requirements for a 10hp motor. I have a 30 & 50 amp available so I imagine I'll be covered for input current.
Please keep the info coming-I really don't wish to take short cuts

Howard,

The full load amps seem extremely high. A NEMA design C, 10 hp motor would have a full load amp rating of approximately 27 amps. I think a photo of the motor nameplate is the next item needed to help figure this out. Thermo King is a manufacturer of refrigration units primarily for refrigerated trucks and such. I do not know what kind of motors they make or re-label. Please recheck the FLA rating and make sure you are not looking at the locked rotor amp rating (85 would likely be too low for the locked rotor rating)

We still need the number of leads and the wire numbers. Since it is dual voltage, we suspect it will have nine leads

You can get run capacitors from www.surpluscenter.com. I am ordering from them presently for two 7-1/2 hp RPCs I am building. They ship quickly and their prices are very reasonable. I seem to remember about $7 for a 40 microfarad (mfd) size oil filled motor run capacitor, but I have not been on line this week to check.

For a starting circuit you need a potential relay (Steveco 90-66 which is about $22 from www.patriotsupply.com, a 3 pole, 240 volt coil, 40 or 50 amp rated contactor which is about $20 or less on ebay, and two electrolytic capacitors, 250 volt rated, and 276-324 micro farad rated, these are about $10 each and make sure they are new). None of these items are in the lights you are talking about. The lights do contain oil filled run capacitors of about 28 mfd rating. I used to have lots fo these but used most of them. Do not buy any of the components till you have the motor wiring figured out and know that it will run.

The starting circuit components will cost about $60 and you still need a way to turn the power on such as a 60 amp disconnect or a 60 amp, 240 volt coil, 3 pole contactor and a stop and start push button set. More on all this stuff after you have the motor working.

The above comments are just to give you some idea of what is needed to make the RPC self starting. I did not include prices and quantities for the run capacitors since you may not need them.

Bruce Norton
Kingsport, Tn

The amount of real power consumed by a 10 hp idler
like that (once it is going) will be between 400 and
500 watts.

Add to that, whatever the load motor draws.

Jim

jim rozen said:

The amount of real power consumed by a 10 hp idler
like that (once it is going) will be between 400 and
500 watts.

Add to that, whatever the load motor draws.

Jim

Click to expand...

Is there any information online that gives idle watts of a rotary phase converter?

Umm, not really that I'm aware of. Maybe somebody
could chime in if they have a better number than mine.

I was scaling to your 10hp motor from my 5 hp idler.

I was curious about how much power was dissipated so I
took the trouble to measure it, which is sort of non trivial.

There's a lot of reactive current flowing so if you amp
clamp the fed lines you will get crazy big numbers. But
the power factor is very low. I did the measurement
a couple of different ways and got between 220 and 240
watts of power dissipated in the idler when it was not
running any load machine. That sort of fits with windage
and bearing losses one might imagine, and also fits
with the approximate heating that happens in the
compartment the converter lives in.

Because it's that small it would take a fair bit of
trouble to check via the watt-hour meter on the house
so I never did that.

So my guess about the idling power consumption for a
10 hp converter, that was just me doubling the number
I got for my 5 hp one.

Jim

Sorry for my typo-of course the amp rating I gave was way off - the tag states 27.5 amps. It turns out the motor was made by Doerr which I understand mode good stuff. It has more than 9 leads - I looked again today but was rushing-w-low light and I think it was either 12 or 15 wires I saw. Could this be due to 50hz option?
In my brief low light look it appears to be a standard NEMA hookup but sorry to say I can't accurately remember it other than T1-T7, T2-T8, T3-T9 were wire nutted together.
Thanks loads-I'm getting close to getting a parts list together.
Any input on this transformer setup I had a gentleman mention?

toolnut said:

Howard,

The full load amps seem extremely high. A NEMA design C, 10 hp motor would have a full load amp rating of approximately 27 amps. I think a photo of the motor nameplate is the next item needed to help figure this out. Thermo King is a manufacturer of refrigration units primarily for refrigerated trucks and such. I do not know what kind of motors they make or re-label. Please recheck the FLA rating and make sure you are not looking at the locked rotor amp rating (85 would likely be too low for the locked rotor rating)

We still need the number of leads and the wire numbers. Since it is dual voltage, we suspect it will have nine leads

You can get run capacitors from www.surpluscenter.com. I am ordering from them presently for two 7-1/2 hp RPCs I am building. They ship quickly and their prices are very reasonable. I seem to remember about $7 for a 40 microfarad (mfd) size oil filled motor run capacitor, but I have not been on line this week to check.

For a starting circuit you need a potential relay (Steveco 90-66 which is about $22 from www.patriotsupply.com, a 3 pole, 240 volt coil, 40 or 50 amp rated contactor which is about $20 or less on ebay, and two electrolytic capacitors, 250 volt rated, and 276-324 micro farad rated, these are about $10 each and make sure they are new). None of these items are in the lights you are talking about. The lights do contain oil filled run capacitors of about 28 mfd rating. I used to have lots fo these but used most of them. Do not buy any of the components till you have the motor wiring figured out and know that it will run.

The starting circuit components will cost about $60 and you still need a way to turn the power on such as a 60 amp disconnect or a 60 amp, 240 volt coil, 3 pole contactor and a stop and start push button set. More on all this stuff after you have the motor working.

The above comments are just to give you some idea of what is needed to make the RPC self starting. I did not include prices and quantities for the run capacitors since you may not need them.

Bruce Norton
Kingsport, Tn

Click to expand...

pics

OK I figured out how to get photo opportunity. Here are the tags along-w-a couple of my other pieces of old USA iron.

Thanks for the help. I was actually able to get the engineering diagram for this "Doerr" Motor from ThermoKing. I spoke-w-a guy at their factory after being sent to a distributor that had no interest in helping me. This nice guy called me back after 3 days and said he found the documentation and emailed it to me. It is setup to run on 230 volts at 60 hz and uses typical NEMA wiring standard for a 12 wire motor so this was a big help. I ordered contactors fuses/holders capacitors etc. so I hope to get it running in the next few days or months? I was planning on using the Fitch method unless this is overkill???? It seems he certainly had a way of getting things balanced but maybe more importantly lowering the current consumed by the idler. Thoughts on this are appreciated-

toolnut said:

Howard,

The full load amps seem extremely high. A NEMA design C, 10 hp motor would have a full load amp rating of approximately 27 amps. I think a photo of the motor nameplate is the next item needed to help figure this out. Thermo King is a manufacturer of refrigration units primarily for refrigerated trucks and such. I do not know what kind of motors they make or re-label. Please recheck the FLA rating and make sure you are not looking at the locked rotor amp rating (85 would likely be too low for the locked rotor rating)

We still need the number of leads and the wire numbers. Since it is dual voltage, we suspect it will have nine leads

You can get run capacitors from www.surpluscenter.com. I am ordering from them presently for two 7-1/2 hp RPCs I am building. They ship quickly and their prices are very reasonable. I seem to remember about $7 for a 40 microfarad (mfd) size oil filled motor run capacitor, but I have not been on line this week to check.

For a starting circuit you need a potential relay (Steveco 90-66 which is about $22 from www.patriotsupply.com, a 3 pole, 240 volt coil, 40 or 50 amp rated contactor which is about $20 or less on ebay, and two electrolytic capacitors, 250 volt rated, and 276-324 micro farad rated, these are about $10 each and make sure they are new). None of these items are in the lights you are talking about. The lights do contain oil filled run capacitors of about 28 mfd rating. I used to have lots fo these but used most of them. Do not buy any of the components till you have the motor wiring figured out and know that it will run.

The starting circuit components will cost about $60 and you still need a way to turn the power on such as a 60 amp disconnect or a 60 amp, 240 volt coil, 3 pole contactor and a stop and start push button set. More on all this stuff after you have the motor working.

The above comments are just to give you some idea of what is needed to make the RPC self starting. I did not include prices and quantities for the run capacitors since you may not need them.

Bruce Norton
Kingsport, Tn

Click to expand...

Fitch Williams designs are the defacto standards for RPC design. Just be aware the 10 hp version with a 40 amp circuit is really a 7-1/2 hp because the circuit is too small. It is a good operating design and will handle load motors up to 7-1/2 hp total load. If you want more total load you will need to increase the circuit size to 60 amps and increase the component and wire sizes accordingly. Fitch used a you hold-it start pushbutton design. Other types include potential relay types and timing relay types. All three methods work when implemented properly. His design does not include oveload protection for the idler and in you case, I doubt that you need it.

>Fitch used a you hold-it start pushbutton design.

I was wondering why nobody seems to be doing that around here. In fact, you don't need to "hold-it" to start, you just push the button like it was a door bell button and the motor is going. In all the ones I have built, the button ( McMaster-Carr # 9209K11 on my latest one for my 14" Clausing ) pulls in a 30 amp two pole relay. One of the relay contacts puts the start condenser in the circuit. The second contact on the relay energizes the motor contactor ( which latches in with its own "seal" contact ). The motor on the one I just built is a 5 horse 3600 rpm motor ( well, whatever it slips to - I'm not out in the shop right now to read the official speed ) and the start condenser is a nominal 300 mfd 250 volt electrolytic ( just the biggest single unit I could buy from McMaster-Carr ). There is a two pole "short lever" switch ( McMaster-Carr # 9209K551 ) which supplies power to both the relay and the contactor coils, which are 120 volt AC coils - one on each line of the 240 volt circuit so that if either side of the 240 volt line is down the whole control box won't try to work because one or the other relay coils won't pull in. The lever switch also lights a 240 volt pilot light ( McMaster-Carr # 7380K5 ) on the control box which tells me that the whole system is "armed". Of course, when I want to shut this thing down, I just turn off the lever switch.

REALLY, just push the button like it was a door bell ( "ding-dong" ). Don't try to hold it in and don't try to beat it like you were afraid you were going to get a 'poke' from the bell button. I'd estimate that I don't have the button pushed in more than about a quarter or third of a second, and by then the motor is running fine.

It's a lot simpler and cheaper than some unnecessary fancy time delay or current sensing relay.

I built one like this about thirty years ago that has been running my 12" Clausing reliably all that time ( except in that one I didn't have a 250 volt condenser handy so it uses a 125 volt one -- and yes, it's still working fine 30 years later ). ( Originally I didn't even have the relay or contactor either. The WHOLE thing consisted of a double switch wall box with a two pole wall switch for the motor 240 volt supply and a single pole "light" switch for the condenser -- mounted side by side in this wall double box. I'd start it by first turning on the single pole "light" switch to put the condenser in the circuit and then with my thumb I'd turn the double pole switch on to start the motor and with my middle finger then I'd turn the "light" switch off to take the starting condenser out of the circuit. Again, I did this as fast as I could do it and the condenser wasn't in the circuit for more than a fraction of a second. I DON'T recommend this! But it worked okay for a couple months before the switch opening arc burned the contact on the "light" switch and I had to replace it. That's when I built the better one with the button and the relay. )

Both of these are in Hoffman 10" by 12" electrical enclosure boxes with three L15-20 sockets along the bottom of the boxes - one for the idler motor and two for users.

If anybody is interested in seeing what this whole thing looks like, I could probably figure out how to post a picture or two of it/them, but at the moment I don't have any idea how to go about doing that.

Kurt

I can use a 50Amp circuit if this is better?? I was under the impression I needed a circuit that was rated for more than the max idler motor current however the more I think about it the more I can understand I would need more if I need to drive more current. Literally I'm using the 10hp because it was $25.00 and look like it has almost no use. I am only driving about 5-10 amps and thats if I put the 3-ph back on my Sheldon.
Correct me if I'm wrong but the Fitch design seems to address a large current consumption variation which I was very surprised to see. The one stumbling block I see is the cap used to "tune" the output is selected-w-no load and most other threads I've seen suggest taking voltage values with a load? Also I've been told that the more 3-ph motors on the RPC the more balanced the legs will be. Is this typical? Lastly I still wonder about an isolation transformer for balancing the legs. I understand the motors I'm running won't fart if the legs are 10vac apart but I like the idea of a balanced output and if I came accross a transformer that was maybe 230 primary/240secondary would this be a good pick up? i believe these are boost/buck transformers.

Hi,

Trust me, ADD the condensers!! Brute force is NOT better. The current draw may not show up on the meter because of the LOUSY power factor, but it sure shows up in the wiring. WHY would you want to draw FIFTY amps (even if it's free) when fifteen would be more like it? Is this in your house? If so, those fifty amps are causing the voltage in your house to sag every time you run the shop motors. You'll have florescent lights flickering all over the house. Yes, those fifty amps ARE real and they screw up everything else in the house in the process, they just don't read on the power meter.

Kurt

Now I know I've not been clear in my post(s)! Sorry. I was meaning to say I have a 50 amp circuit available in my shop run from my 400 Amp panel. I was/am unclear about the input current rating especially since one contributor suggested a 40Amp might be lacking??? I know you were meaning capacitors and not condensors but are you saying add them as per the Fitch design for current tuning? I planned on this anyway but am unclear as to the measurement protocol that being tuning being done-w-no load as opposed to, what I would think would be more real life as in with a load.
BTW -I just built this house and did all the electrical work and wired 105 home runs to 2 40 circuit panels in the garage that are back to back-w-2 12 circuit panels that have the meter pan between them. I ran 12awg min except some small lighting circuits and a few spares to the crawl space and attic. My shop accounts for about 1/3 the potential capacity. The inspectors don't allow anyting that's not gfci in a shop unless it is "dedicated" so I had to run about 8 20 Amp circuits-w-single plug recepticals in each but I changed these out for 4-gang in a few cases where I would be using light loads like cordless recharging, small drill press & blast cabinet. Short story long-no light dimming going on in this house.

Kurt Greske said:

Hi,

Trust me, ADD the condensers!! Brute force is NOT better. The current draw may not show up on the meter because of the LOUSY power factor, but it sure shows up in the wiring. WHY would you want to draw FIFTY amps (even if it's free) when fifteen would be more like it? Is this in your house? If so, those fifty amps are causing the voltage in your house to sag every time you run the shop motors. You'll have florescent lights flickering all over the house. Yes, those fifty amps ARE real and they screw up everything else in the house in the process, they just don't read on the power meter.

Kurt

Click to expand...

The "balancing" does not mean you have all three legs equal. It refers to adding capacitors to the two genereated phases such that the generated voltages are slightly higher than the incoming line voltage. The easy way to 'balance" is to follow Fitch Williams instructions and be done with it. His method works wonderfully. I do the same as he and balance with the idler running and no load motors connected. You try to get the two generated phases about +5% to +10% above the incoming line. One of them will be higher than the other but that is no problem unless you are running a CNC machine. Once you have the RPC 'balanced" per Fitch's instructions you will have a good performing RPC. It is not necessary to balance with the load motor running as most folks run various motors with their RPC. I have run anything from 1/4 hp to 5 hp with my 5 hp RPC and have encountered no problems in some 18 years of usage.

The circuit size needed depends on the total horsepower load you will have on the RPC. Just use the basic equations for converting three phase amps to equivalent single phase amps. single phase amps = three phase amps x 1.732. you need this plus enough to handle losses in the RPC. Hence my comments about Fitch's 10 hp plan is really a 7-1/2 hp RPC and a darn good one. If you want 10 hp capability you will need at least a 50 amp circuit and the cost to build a 50 amp RPC is the same as a 60 amp and hence the reasoning behind building 60 amp,. 10 hp RPCs.

1) it is easy to balance (tune) the converter output using
fitch's instructions.

2) you will reduce the overall power factor of the unit
if you do this.

3) if your load motors are one or two hp total the output
voltages will probably be balanced without adding tuning
capacitors. Better than ten percent I would guess.

4) yes the *capacity* of the system does increase as you
add more load motors on. Not the overall balance per se.

5) the total real power consumption for a 10 hp idler
is going to be around 400 to 500 watts based on my
measurements for a 5 hp one, scaled up.

6) the poor power factor does not 'show up in the wiring'
and does not get measured by the watthour meter.

Jim

Jim wrote: 6) the poor power factor does not 'show up in the wiring'

Hi Jim,

It certainly does, it heats up the wires and wastes energy that the power company isn't getting paid for. That's why the power company gets a bit upset if some significantly large user of power operates with a power factor considerably off of 'the standard average' and they haven't put in a good enough meter to measure what he's really doing.

But what "Challenger" (Did he refer to 3985? Is he a fellow steam freak?) said later (a 400 amp drop and wiring to allow for what he is doing) sort of makes what I was saying a moot point.

Also see my reply to Owen on a different thread about that I'm only using my rotary converter to supply power to ONE machine (a 14" Clausing lathe), so I'm trying to balance it, and minimize the total line current, to include an average of what that one machine uses - especially since it's a hundred plus feet away from the high current carrying wires in the rest of the house. That's obvious to me, but like "Challenger", I forgot to state that in what I wrote.

Kurt

Challenger (really, ARE you a fellow steam freak?) wrote:

>I know you were meaning capacitors and not condensors

Hi Challenger,

No, I was meaning condensers. ;o) I learned my electricity from my Dad when I was ten years old or younger back in the very early 1950s before some 'holier than thou' bunch changed the name of the contraptions! And I never think about the new word. And worse yet, I get all 'tongue tied' if it try to type "capacitor" because I type half of "condenser" before I realize what I am doing, as in 'consnapitor'! ;o)

I also totally refuse to use Heinrich Hertz's name for cycles per second.

You guys will just have to live with it.

>but are you saying add them as per the Fitch design for current tuning?

Yes, definitely.

>I planned on this anyway

Oh. That wasn't clear in what you wrote. I got the impression that you were opposed to the idea and were going to go with the earlier "Hanrahan" design that doesn't use them. I have one of those converters that I made thirty years ago (before I ever knew Jim Hanrahan existed), and it works fine for the three horse idler and two horse lathe motor on my 12" Clausing. But the similar design that I am building now (before I got the condensers for improving it connected into it) was inadequate for the five horse idler and three horse lathe motor on my 'new' 14" Clausing. Its current draw blew the 20 amp breaker so fast that I couldn't even get around to the spot where I could measure the current to see if it was okay! I can only imagine what a ten horse idler motor would do here!! The first cut try at adding the Fitch condensers to it tamed it completely. But by tuning it further to include the lathe motor, it dropped the total line current from in the neighborhood of 17 amps down to in the neighborhood of 10 amps. This is important to me because I've got about 130 feet run of 12 gauge wire out to the back yard shop where this lathe is located and I don't like to see the florescent lights flickering all the time when I'm trying to run the lathe and read the dials on the feed cranks.

>but am unclear as to the measurement protocol that being tuning being done-w-no load >as opposed to, what I would think would be more real life as in with a load.

I completely agree with you as long as you, like me, are only running the converter to supply power to one machine (or to several similar loads operated ONLY one at a time). I would definitely balance it to include that 'average' load. I would only change it from that plan if for some strange reason one of the assorted loads went crazy with this average balancing technique.

But again, with your 400 amp brute force (by my standards) drop and 50 amp wiring, it doesn't really matter all that much for you. So it becomes a moot point of elegance.

Kurt