RPC idler won't come up to speed

D60 · Sep 2, 2009

Specs: Century 7.5hp motor, 1725 rpm, WNY gold series control panel

I first hooked this up w the idler still wired for high voltage 'cause my lack of intelligence can be amazing at times. It'd spin slowly - but faster than it does now wired correctly - then trip the "overload protection" in the gold series panel.

Corrected my error and wired for low voltage. Now it spins slow - if it's more than 80rpm I'd be surprised - then trips the overload protector after maybe 5 seconds or so. Even if I shut it down before it trips, it'll trip the overload shortly after I've hit the red button.

I tried spinning it up w a rope but as soon as I turn the panel on it returns to the same slow rpm before tripping.

At this point I'm stumped, and I'm obviously not an electrical genius or I wouldn't have purchased the pre-made WNY panel in the first place (note I'm not blaming WNY).

A few questions:
1)did I possibly damage something trying to start it when the motor was wired for high voltage, and if so, what, and how can I test it?

2)the motor is a Century E-plus, w stickers talking about how it's more efficient. Is the E-plus somehow not suitable for an RPC or more difficult to start?

3)I see some discussion on which way the idler turns, but does it matter? I swapped lines to reverse it (which it did) but the results are the same

I'm frustrated and I'd REALLY love to be able to use my LeBlond.........

James Rogers · Sep 3, 2009

Check your connections on the motor. Sometimes the 6 and 9 or others can be mis-connected as can other wires. This can cause these problems. To test the motor you can wire it straight from the main panel by connecting the 2 leads directly to the motor winding connections and pull start the motor just as you flip the breaker on. The motor should take off and run. The one drawback to this test is you have to know which direction to pull the rope. If the motor runs correctly I would look at how the WNY panel is assembled.

D60 · Sep 3, 2009

Thanks. Is it possible I damaged the start capacitors when the motor was still wired for high voltage? It did run, albeit slowly, and I did find approx 120VAC at all three outputs, until the overload protector tripped. It did of course groan noticeably, and still groans now that I've wired correctly for low voltage.

I pored over the wiring hoping I had done something like confuse 6 and 9, but no luck.

dave5605 · Sep 3, 2009

I have a WNY gold panel on a 10HP idler and it originally did what yours is doing. Problem was not enough start capacitance.

During troubleshooting I also did as previously suggested. I wrapped a belt around the idler shaft, gave it a big yank (in the correct direction), and immediately hit the start button on the WNY panel. The idler consistently came up to speed immediately doing it this way.

The other problem I had with the WNY panel was no bleed resistors on the start capacitors. WNY would never respond to my queries either. The folks here saved my 'bacon'.

I assume you have no load on the RPC/idler when doing all this, right?

D60 · Sep 3, 2009

dave5605 said:
I assume you have no load on the RPC/idler when doing all this, right?

Correct, no load whatsoever.

So I did as James Rogers suggested and wired the motor directly to my breaker. The third leg of course has no power coming into it but I tied them together (wires 3 and 9)

I spun it up as best I could w a rope in the correct direction and flipped the breaker. I get an identical result as when wired thru the WNY panel: motor groans and immediately drops down to very low rpm.

It literally brakes the shaft down from [rope speed rpm] to [very low rpm, guessing under 100rpm]. Presumably it would continue like this until I allow it to cook itself, the wires, or trip the breaker.

So, does this sound like bad motor? Or am I simply not generating enough speed w the rope?

Shawn Ghormley · Sep 3, 2009

Hello, can you post pictures of the RPC inside and out. Shawn

J_R_Thiele · Sep 3, 2009

Someone in the past indicated in a post they had a motor that did this- but only if they had it rotating it and then tried to start it. If they had the rope attached hit the power switch and then pulled it took right off.

I have a motor which does this- and so noted the above- but have not tried it yet.

I would be VERY CAREFULL to not have the rope wrapped around you had, wrist or body. If somehow it takes off the wrong direction you do not want to be pulled into it

I am guessing the speed it is rotating at is a "multiple" of 60 hz and it in some way is acting as a servo motor. Mine seemed to slow down to follow its chosen RPM.

D60 · Sep 3, 2009

J_R_Thiele said:
Someone in the past indicated in a post they had a motor that did this- but only if they had it rotating it and then tried to start it. If they had the rope attached hit the power switch and then pulled it took right off.

I have a motor which does this- and so noted the above- but have not tried it yet.

I tried this, but same result. Turned on the breaker and then pulled the cord... motor is insistent upon going SLOW.

At one point I turned the breaker off, let it come to almost a complete stop and flipped the breaker back on, at which point the motor self reversed?? but at the same glacial speed.

I never let it run for more than a second or two when testing, but it still eventually began making bad smells and tripped the 40A breaker. No visible smoke, FWIW

D60 · Sep 3, 2009

Damn, one more thing: I do have a 5hp 3ph motor lying around. I'm not certain if it's ok to try this w the 7.5hp control panel?

James Rogers · Sep 3, 2009

The 5 should be fine on the 7.5 panel. The panel probably has bigger or more capacitors as a difference. You could try disconnecting the legs on the 7 from themselves and ohm them to make sure you have continuity in all 3 phases individually. I had a 3 HP motor with a broken leg internally that would run but was slower than the 1750 RPM max on the spec plate. Sounds like a broken or burnt winding.

James Rogers · Sep 3, 2009

Another thing, is the motor delta or wye? If you wire it wrong it will do just as you describe. Let us know what the type it is, delta or wye and we can diagnose the wiring. I have 25 HP I wanted to test and wired it delta and got the same results you did. I wired it wye and it ran great. Nice for a free motor.

James Rogers · Sep 3, 2009

Try wiring it in the delta mode. This would be 4-8-2 / 3-5-9 / 6-7-1. You won't loose anything and it might work. Just because the plate says wye does not mean it was never rewired different or the box was never changed.

rons · Sep 3, 2009

D60 said:
Specs: Century 7.5hp motor, 1725 rpm, WNY gold series control panel

Corrected my error and wired for low voltage. Now it spins slow - if it's more than 80rpm I'd be surprised - then trips the overload protector after maybe 5 seconds or so. Even if I shut it down before it trips, it'll trip the overload shortly after I've hit the red button.

It's time to get out the ohm meter and check that the windings are equal in
impedance. And then check that your splicing connections are correct so that
your windings are not being connected into the wrong poles. Understand ?

D60 · Sep 4, 2009

rons said:
It's time to get out the ohm meter and check that the windings are equal in
impedance. And then check that your splicing connections are correct so that
your windings are not being connected into the wrong poles. Understand ?

Not sure I totally do. To check the windings I do what exactly? And how do I know if I'm connecting to the wrong poles?

BTW I took the motor to my former employer today which has 3ph. The motor happily fired up on 3ph, wired for wye: 4,5,6 together, lines into 1/7, 2/8 and 3/9

I don't understand why I can't pull start this 7.5 motor, tho. I even spun it up w my 3/8" impact yesterday but as soon as I give it power (connected directly to my single phase breaker) it insists upon bogging way down. I *was* able to pull start the 5hp motor yesterday (which is a 3450rpm at that) hooked directly to the breaker, just to confirm that my methodology is somewhat sound.

D60 · Sep 4, 2009

*Update*

I reconnected the motor and tried a few small things, none of which helped. Finally I figured I had nothing to lose and spun the motor up w my 1/2 impact (IR2131 if anyone's counting) which I had previously figured would simply be overkill. I got it up to matched speed w the impact and hit the button on the control panel, and it actually worked.

So, all this for nothing. I apologize for being a typical newb. It now appears however that I need more start capacitance, same as Dave5605. I did search his other posts hoping to find how he resolved his problem, but could not. Presumably the forum only saves info for a finite amount of time.

Presently the control panel has two start caps rated at 270-324mfd. I'm not sure if I should get more of these, or step up to larger start caps altogether? One of the start caps has what appears to be a resistor on it, is this bleed off (not that I know exactly what that means)?

BTW in searching I did find this thread complaining about WNY
http://www.practicalmachinist.com/vb/showthread.php?t=177919
wish this had come up in my search here BEFORE I ordered from them. I had a similar experience, it took almost exactly one month to receive my panel, and he significantly mis-spelled the name of my city on the address label. It required at least 4 inquiries to get a response, and the only one I did get was via PM on this site. Also something weird went on with the shipping because UPS "redirected" the package, causing nearly a week delay in shipping. Almost verbatim other complaints on this site. I wasn't gonna say anything until I found that these practices have apparently been going on for some time.

rons · Sep 4, 2009

D60 said:
*Update*

Presently the control panel has two start caps rated at 270-324mfd. I'm not sure if I should get more of these, or step up to larger start caps altogether? One of the start caps has what appears to be a resistor on it, is this bleed off (not that I know exactly what that means)?

If it is across the two terminals then it is to discharge(bleed) the cap after it
is switched out.

toolnut · Sep 4, 2009

I normally use two fo the same capacitors in my 7.5 hp designs and they work fine. You can add some more caps but look at how the caps are switched. If you have a 3 pole contactor look to see how many amps it is rated for. Here is a rough guideline for the amount of capacitance you can put one each pole.

30 amp start contactor: put approx. 300 mfd of start caps on each pole. this is the size caps you have and I suspect it is the start contactor size also. If it is a 3 pole contactor, you can put one of the 274-325 caps on each pole and each one needs its own #10 wire to and from. This will give a total of approx 900 mfd and that should get the motor going.

40 amp start contactor: put approx 400 mfd of start caps one each pole. this cap will produce about 40 amps of current and you need to wire with #8 wire or if you use two caps to arrive at the 400 mfd amount, Assuming the start contactor is before the caps, you can wire to the contactor with #8 wire and from the contactor to the caps with a #10 to each cap then a #10 from each cap back to the generated leg.

50 amp start contactor, put approx 500 mfd max. this will produce approx 50 amps and you need to use the appropriate wire. I am sure your contactor is not this large.

the figures are approximate and are slightly conservative. it is easier to remember these numbers than calculate the actual maximum mfd allowed which will be about 10% higher.

dave5605 · Sep 7, 2009

I added one 320-384 start cap to the two existing 270-324 caps. Paralleled it with one of the existing ones. This was to get a 10HP idler running.

I realized the contactor was marginal for this much capacitance but it has lasted so far for about 30 starts (home environment).

In your case I'd just add a 3rd capacitor(maybe another 270-324?) and try it.

I'm sure up in the design sticky in this forum somewhere they say how much total capacitance to have for a 7.5HP idler.

I got my caps on ebay for a cheap price. Do a search for start capacitors. Same for the bleed resistors. Got the crimp connectors at the local auto parts place.

I'll have to say everything in my 'gold' panel seems to indicate it was for a 5HP idler (bare minimum/ not heavy duty) and just the outside sticker is for 10HP. :crazy:

D60 · Sep 7, 2009

Thx all. I have a 40A contactor, so I just ordered two 340-408 start caps to replace the existing ones because I suspect they weren't happy w me as long as I tried to run the motor when it was improperly wired for high voltage. I'll step up to the appropriate AWG for the larger caps, too.

The panel came to me w a resistor on only one start cap, is this ok? Or does each start cap need its own bleed off resistor?

rons · Sep 7, 2009

D60 said:
The panel came to me w a resistor on only one start cap, is this ok? Or does each start cap need its own bleed off resistor?

I assume from what you said that there are few start caps wired in parallel to
obtain the capacitance. Then only one bleed resistor is necessary. You might
as well check the value of that resistor. If you don't know how to read color codes then use a ohm meter.

RPC idler won't come up to speed

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