2 hp elec motor question

[danno]

Any electric motor heads out there?

VERY frusterating vacuum issues this year. Tore the Delaval 75 pump down tonight and the pump seems fine, but still having motor headaches.

Had the motor re-coiled last week cause mice tore through it in the off season. Now I can't get the motor to drop out of start mode. Motor is running on 220. I've got 237 volts at the plug - motor starts at 53 amps but will not drop down. Took it back to the shop that rec-coiled. He put it on his 245 volts and motor amps dropped right down to 12ish. I got the pump running at low amps yesterday at home, but again today I could not get it to drop out of start mode. When I take off the belts (no load), motor runs fine and drops right down to 6ish amps.

I've run this same pump/motor for the last two seasons with no problems. Breaker and all connections are good. How can I delay the load of the pump for just that second to allow the motor to drop out of start?

All ideas welcome!

[KenWP]

I am wondering if it's not getting enough power to start proper so that it will drop back down. Did you change the wireing to the motor any. Your saying with no load it drops back to run cycle but with load it dosn't. Thats a clue it's not getting enough juice for some reason. Maybe heavyier wireing will help.

[sapsick]

it appears they motor is fine until you hook your pump to it. is there some sort of a pressure switch on these? what tells this pump to start making vaccuum or to stop?when its running are you creating vaccuum i believe the amps will come down as your inches of Hg go up.

[danno]

Gosh darn, sniggerin *#$#$&*%$# motor.

Through heck or high water, I was gonna get my vacuum going. Started the motor this morning with the belts completely loose so no load. Motor starts fine that way - then backed the motor away from the pump to engage the belts and tightented the bolts down. Not a great way to start the vacuum every day, but at least I've got the vacuum going!

[sweetwoodmaple]

Hey danno...just throwing something out there...chalk it up to the value of free advice if they don't apply.

Is this a capacitor start motor? If so, there is a centrifugal switch that controls when the high current start windings drop out and the regular windings come in. When hooked up to the vacuum pump load, I'm sure the RPM's are slightly lower...therefore this switch may just be on the edge of working. If the capacitor was bad, of course it would just hum and not start.

If you knew where this was, you could put a little switch to bypass and run the start/run windings manually.

Again...sometimes free advice is worth what you pay. Hope you can get things figured out...seems like the beginning of the maple season has all the bugs...instead of the end when the weather is warm! LOL

[Brent]

I agree with Brian. I think it's not getting up to speed to trip the switch. Did the motor get wet or get sap splashed in it. Maybe some gunk, like mouse pee. Something is stopping the switch from tripping at the full load speed with the pump connected ... different from last year, when it apparently was tripping at the same speed that it won't trip at this year. Maybe one of the springs in the switch.

[danno]

Brent and Brian - you're on the righ track, but we just can't figure this bugger out. Spent too many hours working on it again today. We've determined it's the power source, not the motor. We put another motor on the system - same as the first. Runs great with no load, volts drop from 240 to 210 and amps run at 55 on the 2hp and 90 on the 3hp.

Checked all our connections, power at the house, etc, etc.

One thing we did find. We're dropping alot of volts on the 150' run from the house to the motor. Volts drop to 221 in the house, 210 at the motor - and that's just not enough to kick out the start switch. We running 10/3 direct burial.

Just does not make sense as this system has run fine the last two years. Keep the ideas coming. I have been starting the motor with no load, then backing the motor out to engage the pump, than tightening down the nuts. It's a pain, but at least I've got vacuum.

[danno]

Brian - the capicitor's were changed out when the motor was re-built couple weeks back. We did check the capictors today. They tested fine but my buddy was surprised that both capictors were the same. He was expecting one start and one run capicitor. But other motor had two same capictors as well. Should capictors be the same?

And we have seen this syrem work under load at the shop that re-built it. And once, the motor under load did work at home.

[Brent]

that voltage drop is not that bad when you're drawing such a big current. If the same rig ran on it previously I'd trace the line and check every connection, re-seat the circuit breakers, fuses, tighten the screws in the circuit breakers and switch, then try again. If there is a loose connection with that much current it could become a hot spot / fire source.

[KenWP]

I figured it was not enough current for the motor to click it's self out. Your running 10/3 wire but the motors drawing almost on the max side of what the wire can handle. Also there can be one screw in the line someplace that's just not tight enough or corroded. You might have to invent some kind of arm that the motor sits on that tensions the belts with the motors weight like the old table saws used to use. Then you can just lift it a bit well starting and let it down and be done in seconds. Might be faster then

[Haynes Forest Products]

Do you have a smaller drive pully not much just enough to get the RPMs up a little?

[danno]

Haynes - how would a smaller pulley reduce the load at start? Really, any load on the motor is causing it not to drop out of start. Once the pump is good and warm, if I turn it off for a minute, it will kick back on in run mode.

Ken, yea, I'm thinking some kind of lever system to engage the belts may be the way to go.

Brent, we've checked every connection, fuses, breaker, etc. We also tried by-passing all connections and wired from the cable directly to the motor. Still having voltage drop. Now we are thinking either bad connection in the meter or transformer. Only other thing I guess it could be is the 10/3 direct burial?

Guess I can't ask my wife to turn on the vacuum in the morning after I leave for work any more. Guess I'll have to start going in late:)

[Brent]

Well from what you've said the electrical side should be OK

You say you've had the pump apart and the motor, so here's an idea that we find often helps in the machine tools we sell and service. Frequently when a set of bearings is replaced they do not go back on exactly where they used to sit and create a preload condition that causes more drag and head than before the rebuild. We get the drive train up and running and let is go long enough to warm up the whole assembly. Fits of bearings on shafts and in their housings change in the heating process. Then we take a hammer and rap the shafts on each end. The shock often is enough to make the bearing jump into position where there will be less load. Sometime when we do this you can hit the shaft once and hear the difference instantly when the load comes off the bearings. Don't know if you can get at both ends of the pump crank but you should be able to get at both ends of the motor pretty easy. Don't swing like you're trying to split wood, but give it a good rap.

[mnguy]

Danno,

That 2-HP motor at 240 volt should only be pulling about 10 amps when it is running. I think you said it is pulling 55 amps. If this is the case that it is actually pulling 55 amps I agree with Brent seeing you just had it rebuilt that something is to tight in the motor and making it turn hard and this will drive your amperage way up on it. I myself I would take the motor back to where you had it rebuilt and explain to them what is going on. If you keep trying yo run it with it pulling that kind of amps you will just burn up the motor.

[Haynes Forest Products]

Danno I was comenting on the discussin that if the motor ran at a higher RPM it would change over. If your looking to make a quick clutch system hinge the inside motor platform so you can lift it up and towards the pump. Then you can use a spring, Bunji cord, Or small ratchet strap to put tension on the motor to keep the belt tight. You could even put a counter weight to hold the motor down so all you do is pick up the weight and start motor let it spin for a few seconds and then let the weight down and slowly get the pump moving Its easy even a girl could do it.

[danno]

Haynes - good idea about the hinge. I like it. Brent, we did try seating the bearings with a hammer tap, no luck. MNGUY, motor runs about 7 amps in run mode and about 12 while under load. Just runs 58ish at start up.

[KenWP]

The hinge was what I told him to do in a eailier post DUH guess only certain people can post. Owell.

[Brent]

Ok lets try another angle. You said the motor was rebuilt.
What did the motor shop do ?
Replace bearings, replace capacitor, rewind the stator, replace the start / run switch ?

What was the motor rpm before the rebuild. Any chance it was a 1200 or 900 rpm motor and it got rewound with the wrong number of fields ?

If there's nothing in that idea I'd trash the capacitors and start / run switch and start over. They've got to be connected wrong on the wrong capacitance or they've already blown.

[maple flats]

My calculations say you should be running 8 ga for 150', or the start up voltage will drop too far to kick back to run amps. Not sure how you got away with it before.
Good luck!

[Brent]

One more thought. From the little I know of dairy vac pumps, I think most run with slow speed motors. If the start run switch was replaced with one for a standard speed, 1800 rpm motor, then it would have a real problem switching over to the run mode.

[Haynes Forest Products]

Sorry KenWP I didnt see the word "HINGE" in your post:emb:

[danno]

[QUOTE=Brent;103409]Ok lets try another angle. You said the motor was rebuilt.
What did the motor shop do ?
Replace bearings, replace capacitor, rewind the stator, replace the start / run switch ?

The shop replaced the capacitors and rewound the stator. Motor runs at 1620 rpm.

I've seen this run fine at the shop, so I wonder if it's wire size. But then again, its run fine on that wire for 2 years. Maybe after season, I'll bring the pump closer to the house and see if it will run and try to determine if it's the motor (don't think so), wire or power supply.

[danno]

The saga continues - went to start up this morning and there was some ice in the releaser outlet preventing the flap from closing - thus allowing the pump to suck free air and reduce the load just a bit. This allowed the motor to switch into run mode without having to loosen the belts - or at least that is what I expect caused it to start fine this morning. Down to 25 last night, so the oil should have been pretty stiff. Hum...

Anyway, hoping for a good run today!