115V/220 motor wont start but runs fine if I give it a push

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metron9
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Posted by metron9: Sun. Feb 6, 2011 - 07:40 AM
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I bought this motor from surpluscenter. It is not used but I don't know when it was made.

http://www.surpluscenter.com/ite...

I connected it up and it just stalls when applying 115VAC but if I give it a spin it runs fine. It has a little spring loaded gizmo on the fan side that connects the capacitors and it has 3 capacitors, 2 160uf and 1 35uf. Could the capacitors just be hosed, how do I test them? Should i just be able to put a single capacitor instead of the three if the caps are bad?

Should I just buy a new motor because this one is a piece of junk?

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Learning and Information, General Electronics
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bobgardner
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Posted by bobgardner: Sun. Feb 6, 2011 - 08:05 AM
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It says it is capacitor start, capacitor run. The little spring loaded thing must be a centrifical switch to switch from start to run. There's got to be a wiring diagram on google. Gotta be.

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david.prentice
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Posted by david.prentice: Sun. Feb 6, 2011 - 08:44 AM
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Google for a Brooks catalogue. It shows the wiring.

If your motor is not starting, the centrifugal switch is probably stuck open.

Wire a push-button switch across it. Then 'push' to start. Release when running.

The centrifugal switch may free itself over time.
You may enjoy 'fiddling' and applying WD40 in a strategic spot. It is up to you to find that spot. And not get WD40 where it should not go!

David.

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ignoramus
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Posted by ignoramus: Sun. Feb 6, 2011 - 08:47 AM
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Dont fiddle like Nero... afterall 115V is more dangerous than 240V

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steve17
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Posted by steve17: Sun. Feb 6, 2011 - 12:16 PM
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ignoramus wrote:
115V is more dangerous than 240V
That must be an Australian thing.

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ignoramus
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Posted by ignoramus: Sun. Feb 6, 2011 - 12:54 PM
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Steve its to do with the muscle response to different voltage levels..

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metron9
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Posted by metron9: Sun. Feb 6, 2011 - 03:48 PM
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Yes it is a spring loaded centrifugal clutch enclosed with a plastic housing. I did remove the housing and watched it, it does work as it should, opens when running and closes when stopped. There is a wiring diagram on the plastic enclosure and it is wired according to that diagram. I will have to read up on how the capacitors work to start a motor so that I can better diagnose the source of the problem.

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tpappano
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Posted by tpappano: Sun. Feb 6, 2011 - 05:38 PM
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Check the 160uf caps to make sure they are still "caps". Motor starting capacitors are usually non-polarized electrolytics, and eventually they can dry out or fail for various other reasons. If the centrifugal switch seems OK, then the starting capacitor(s) is probably bad. The 35uf part may be a "run" capacitor, and likely a paper/oil style which rarely fails.

Tom Pappano
Tulsa, Oklahoma

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metron9
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Posted by metron9: Sun. Feb 6, 2011 - 07:29 PM
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I have read various ways of testing the caps, I will give that a go and also see if my motor friend has a couple of extra 160uf start caps.

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tpappano
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Posted by tpappano: Sun. Feb 6, 2011 - 08:28 PM
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These caps are fairly cheap, too. You can get them at HVAC parts suppliers like Johnstone Supply, or WW Grainger if you don't mind paying a bit more.

Tom Pappano
Tulsa, Oklahoma

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metron9
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Posted by metron9: Sun. Feb 6, 2011 - 11:28 PM
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I just did a 28V dc spark test. I have a 470UF dc cap (I know I can't use a DC cap on the motor) But the 2 160uf AC caps are in parallel so i assume 320UF charged with 28VDC would provide a pretty good spark when shorting. Not much spark compared to the 470uf DC cap so I assume the caps are just not doing the job. They also drain very fast when just watching the voltage on a meter after charging them. They drop 10V in just 20 seconds. The DC 470uf dosen't even drop 1V after 20 seconds. I will order some new caps.

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angelu
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Posted by angelu: Sun. Feb 6, 2011 - 11:45 PM
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If you have a low AC power supply available, just connect the capacitor and measure the current with a meter.

Xc = 1 / (2 * PI * 60 * C)

I = U / Xc

I = U * 2 * PI * 60 * C

So for 24Vac, 60Hz, 160uF, you should read 1.45A.

George.

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metron9
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Posted by metron9: Mon. Feb 7, 2011 - 12:21 AM
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Hmmm I have a 4.8VAC transformer unregulated . Using that I get a voltage across the cap of 5.7VAC and when I check the current through the meter I get 330mA so that looks like the caps are ok then?

I am not understanding the formula (not good at reading math unless the actual numbers are used Xc and U and PI ??)

so I used 24V / 5.7V = 4.21 and then used 1.45A / 4.21 and get 344mA I guess would be the target so 333 is close but how close does it need to be?

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angelu
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Posted by angelu: Mon. Feb 7, 2011 - 12:39 AM
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Yes, it looks like they are OK.

With proper capacitors the motor should start even under the load. If the capacitors are the problem and the motor is not able to start with no load, this mean the capacitors should be dead completely. According to your measurements, the capacitors are not dead.

There are different connections depending you power the motor with 120V or 240V. Are you sure everything is connected properly ?

Post a picture with the connection diagram ?

Maybe it is in 240V configuration and you test it at 120V? I just ask.

Check to see if after start it powerful enough.

George.

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metron9
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Posted by metron9: Mon. Feb 7, 2011 - 01:56 AM
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Ok, Power is good when running so no problem there.

Here are the pictures. The wiring diag shows to swap 5 and 6 to run counter clockwise and that is what I did.

There are 2 wires labeled T5. The T5 wire comming out of the motor is tied to T8 from the factory. The other wire labeled T5 is connected to the three capacitors so in connecting 4,2 and 5 I used this one.

I don't have a snap ring remover at the moment so I can't remove the housing on the centrifugal clutch gizmo but I assume it connects T7 to T5,T8 when the motor is not running. I will disassemble it Monday unless you see something I did wrong here.

Pictures and the wire diagram I made showing a better view of what is connected to what.

I should note, most of the time it will start up if I remove the belt so it's just the motor with zero load (except the pulley) When it does not start up it changes directions back and forth like a vibrator. It just needs a nudge to get it going then it takes off like a rocket. There is very little load when the belt is connected, It is a 4 inch driving a 2 inch pully but free spinning.

Attachment(s): 

Image icon saw1.gif
Image icon From motor housing cover
Image icon MotorSch.png
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John_A_Brown
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Posted by John_A_Brown: Mon. Feb 7, 2011 - 08:11 AM
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Quote:
Dont fiddle like Nero... afterall 115V is more dangerous than 240V

This statement interested me, so I tried a bit of Googling.
One of the first things I found was this:
http://www.techrepublic.com/forum/discussions/10-147374-1579357
At which point I lost the will to continue.
(Just to be clear; I'm not implying that ignoramus subscribes to this particular theory).

Four legs good, two legs bad, three legs stable.

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ignoramus
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Posted by ignoramus: Mon. Feb 7, 2011 - 09:07 AM
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John,

an intersting point of view.. but no I do not subscibe to THAt idea.

I simply stated that 115V IS more dangerous than 240V.

I then further went to say that this was due to muscular reaction to the two voltages.

I am led to believe that at 115V the muscles will contract and the victim will not be able to release the grip.

Obviusly the same thing will happen at 240V however the reaction is potentially much more violent and the victim may not have the time to grab the conductor since the other muscles in the body will react and contact so retracting the limb away from the live wire.

If You pardon the pun...I have no first hand experience of this.

All of the above is hearsay only.

EDIT.. may be I ought to start a new thread entitled Is 115V AC more lethal than 240V AC

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Mongooose
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Posted by Mongooose: Mon. Feb 7, 2011 - 12:55 PM
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Don't mean to drag this off topic, but electrocution is pretty serious stuff. I would say the 240VAC is more dangerous. I was taught a few semesters ago that you model the human body as a resistor to calculate the current. Due to OHMS law you will always have more current go threw you if you apply a higher voltage. It is about 1500 Ohms for in one limb and out another,( limb = 150 Ohms, torso = 200 Ohms, dry skin = 500 Ohms, wet skin = 200 Ohms) figuring dry skin if I remember all of this correctly, less resistance for wet skin.
Found some information in a quick search here:
http://www.tpub.com/content/et/1...

In the case here, (assume 1500 Ohms), 120VAC would be 80mA in the range to cause death, and at 240VAC you would get twice the current 160mA which can kill you faster.
There is also a consideration for time exposed to the current across your chest, longer duration less required to kill you....

Edit: to correct simple math error, and the simple things can kill you... thanks for the correction tpappano

Last Edited: Mon. Feb 7, 2011 - 10:37 PM
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metron9
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Posted by metron9: Mon. Feb 7, 2011 - 02:57 PM
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I can say this about 110VAC

When I was 15, I was helping my dad remove a center island wall from our kitchen area. It had an outlet in it and i was removing the outlet. he said, the power was off so I graqbbed the whole outlet and got both sides of the 110 connections. I was able to let go but boy did that sting. Never again , I make sure it's off and even then I short the wires together before touching them and wear rubber shoes on concrete. I think it matters more where the points are on the body the electric flows through, if you stand on a concrete floor with bare feet and touch the mains, I don't think it matters if it's 110 or 220 both can kill you.

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steve17
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Posted by steve17: Mon. Feb 7, 2011 - 04:38 PM
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Homes in the US have hot wires that are 120 volts from ground. Some appliances use 240 volts, but that is done with 2 hot wires that are 120 volts from ground but are 180 degrees out of phase.

I think some places supply 3 phase power. That's the ideal way to power an AC motor because there is no need to generate a 2nd phase temporarily to get the motor started.

In countries that use 230 volts for everything in homes, are the hot wires 230 volts from ground?

I think most electric shocks involve ground or a metal enclosure that is grounded.

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mossige
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Posted by mossige: Mon. Feb 7, 2011 - 04:55 PM
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metron9 wrote:
Yes it is a spring loaded centrifugal clutch enclosed with a plastic housing. I did remove the housing and watched it, it does work as it should, opens when running and closes when stopped. There is a wiring diagram on the plastic enclosure and it is wired according to that diagram. I will have to read up on how the capacitors work to start a motor so that I can better diagnose the source of the problem.

50 or 60 Hz?
If 50, wrong cap?

HM

HM

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tpappano
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Posted by tpappano: Mon. Feb 7, 2011 - 07:56 PM
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Quote:
In the case here, (assume 1500 Ohms), 120VAC would be 8mA and muscle reaction would be to let go instantly, while at 240VAC you would get twice the current 16mA which is above the 10mA point where you change to involuntary muscular contraction, usually resulting in clenching whatever is shocking you.

You might want to check your math...

Tom Pappano
Tulsa, Oklahoma

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JohanEkdahl
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Posted by JohanEkdahl: Mon. Feb 7, 2011 - 08:15 PM
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Quote:

In countries that use 230 volts for everything in homes, are the hot wires 230 volts from ground?

Yes. Sweden uses 230 Volts (or is it 240 Volts now? In my youth it was 220 Volts.) Three phases at 0, 120 and 240 degrees. Between a phase and ground you get 230 Volts. Between two phases 380 Volts. The latter is used eg for (some) electric radiators, three-phase motors etc.

If we get someone from Norway in here, we might be told about the Norwegian two-phase system.

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bobgardner
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Posted by bobgardner: Mon. Feb 7, 2011 - 09:05 PM
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Motor discussion: general electronics Biomedical discussion: offtopic

Imagecraft compiler user

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Mongooose
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Posted by Mongooose: Mon. Feb 7, 2011 - 09:28 PM
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Quote:

You might want to check your math...

Ok, care to explain?

Edit: PM sent to tpappano, try not to derail this thread any more....

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metron9
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Posted by metron9: Tue. Feb 8, 2011 - 05:31 PM
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Well it is 60HZ to answer one question above. I replaced the caps and still it won't start with any load at all. I removed the housing and checked the clutch cap connector and it works fine, caps are connected when off and disconnect when rotating. I think the motor sucks rocks but I will just leave it on and use my foot to start the rotation. I have spent too much time with this stupid motor unless someone can give me a different wiring arrangement I will give it one last try.

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