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 Post subject: 4-Wire AC motor W/run cap only
PostPosted: Oct Tue 08, 2019 2:24 pm 
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Gents,

I need a wiring schematic for a fractional HP AC motor that uses a [run] capacitor only. The present [ancient] cap get very hot in about 15 minutes. Also, there are 4 wires that run to this motor. I find only start/run schematics when doing a Google search.

Thanks,
Jack


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 Post subject: Re: 4-Wire AC motor W/run cap only
PostPosted: Oct Tue 08, 2019 2:46 pm 
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Jack Cureton wrote:
Gents,

I need a wiring schematic for a fractional HP AC motor that uses a [run] capacitor only. The present [ancient] cap get very hot in about 15 minutes. Also, there are 4 wires that run to this motor. I find only start/run schematics when doing a Google search.

Thanks,
Jack
This variety of motor is known as “permanent split capacitor” or “PSC.”

More info can be found here (scroll down to find the section for “permanent split capacitor motor”)

http://en.wikipedia.org/wiki/AC_motor


Your motor has 4 wires instead of 3. This permits changing the direction the motor rotates (clockwise or counter-clockwise) by reversing the phase of one of the 2 motor coils relative to the other coil.

-EB

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 Post subject: Re: 4-Wire AC motor W/run cap only
PostPosted: Oct Tue 08, 2019 10:45 pm 
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You should be able to trace the connections out with an ohmmeter. There are two common variations on this theme:

1. Two windings in parallel, with the capacitor in series with one of them. Usually seen on 120-VAC motors.

2. Two windings in series with the capacitor in the middle, between them. This arrangement is more often found in motors made for 208-240 volt operation.

As noted above, reversing the connections to one of the windings will reverse the direction of rotation.

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 Post subject: Re: 4-Wire AC motor W/run cap only
PostPosted: Oct Wed 09, 2019 2:29 am 
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So, are there definite START & RUN windings or are the windings identical to each other ?

Jack


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 Post subject: Re: 4-Wire AC motor W/run cap only
PostPosted: Oct Wed 09, 2019 2:39 am 
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Jack Cureton wrote:
So, are there definite START & RUN windings or are the windings identical to each other ?

Jack
i suggest keeping the wiring the same as it was originally.

“Start” and “run” aren’t the best words for identifying the windings because both are powered all the time.
    One winding is connected directly to the AC power.
    The other winding is also connected to AC power, but with the capacitor in series with it.

Does this motor have a label or nameplate on it?
Is it possible for you to post photos of it?
What is the DC resistance of each winding?

-EB

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 Post subject: Re: 4-Wire AC motor W/run cap only
PostPosted: Oct Wed 09, 2019 11:25 am 
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What are the resistances of the windings? If it is a permanent split capacitor motor, they should be nearly the same. There is no start winding per se, since the two windings and capacitor effectively create two magnetic fields displaced by some angle in the motor, making it self-starting. On the other hand, a start would normally have a different resistance than the main running winding. If that's the case, the one with the higher resistance is the start winding.

In motors with true start windings, there is always some kind of switch or device that cuts the winding out of the circuit when the motor gets up to speed. This may take various forms: a centrifugal switch inside the motor, an external relay, or sometimes a positive temperature coefficient varistor. In some cases a small run capacitor is connected across the switch to keep the start winding energized at low power with out-of-phase current, enhancing the running characteristics of the motor.

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 Post subject: Re: 4-Wire AC motor W/run cap only
PostPosted: Oct Thu 10, 2019 1:24 am 
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Chris108 wrote:
What are the resistances of the windings? If it is a permanent split capacitor motor, they should be nearly the same. There is no start winding per se, since the two windings and capacitor effectively create two magnetic fields displaced by some angle in the motor, making it self-starting. On the other hand, a start would normally have a different resistance than the main running winding. If that's the case, the one with the higher resistance is the start winding.

In motors with true start windings, there is always some kind of switch or device that cuts the winding out of the circuit when the motor gets up to speed. This may take various forms: a centrifugal switch inside the motor, an external relay, or sometimes a positive temperature coefficient varistor. In some cases a small run capacitor is connected across the switch to keep the start winding energized at low power with out-of-phase current, enhancing the running characteristics of the motor.


There are definitely 2 windings. One reads 126 ohms, the other, 78 ohms. I'll attempt to send a picture of the label.

Jack


Attachments:
Fan motor needing Capacitor.JPG
Fan motor needing Capacitor.JPG [ 503.18 KiB | Viewed 1897 times ]
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 Post subject: Re: 4-Wire AC motor W/run cap only
PostPosted: Oct Thu 10, 2019 5:45 am 
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After browsing through a bunch of data for PSC motors, I’ll make an educated guess that the capacitor should be in series with the winding that has the larger DC resistance. And the winding with lower DC resistance goes directly to 120V AC.

The 4uF capacitor must be a “motor run capacitor.” A 4uF capacitor made for a ceiling fan should work OK. Ceiling fans have the same type of motor (PSC - permanent split capacitor).

-EB

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 Post subject: Re: 4-Wire AC motor W/run cap only
PostPosted: Oct Thu 10, 2019 6:39 am 
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Thanks EB, I might just have one.

Jack


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 Post subject: Re: 4-Wire AC motor W/run cap only
PostPosted: Oct Thu 10, 2019 11:37 am 
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By fractional horsepower motor, I thought you were talking about something like a 1/8-hp, 1/4-hp, or some size like that. The little EAD blower motor pictured is much smaller. EB is correct in what he says above; in that type the two windings have different resistances, and the capacitor goes in series with the winding that has the higher DC resistance. With a fan blade or other load on the shaft, it runs as a two-phase motor, quieter and with less vibration than an ordinary shaded pole fan motor.

It would be interesting to know what kind of blower that motor was originally intended for. Most EAD motors intended for blower duty were non-reversible and have three wires. The capacitors supplied with the older motors were almost always paper or paper in oil. Stability is important, so non-polarized electrolytics were not recommended. A modern 4-uF, 250-VAC plastic film motor run capacitor will work fine.

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 Post subject: Re: 4-Wire AC motor W/run cap only
PostPosted: Oct Thu 10, 2019 3:51 pm 
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OKAY, I put the original cap. in series with both windings [one at a time]. Neither would self-start and with a manual twist if the shaft, it would rotate in either direction. I just believe the capacitor is BAD, BAD. Here is another pic.

Jack


Attachments:
EAD Motor, Fan & Original Cap.JPG
EAD Motor, Fan & Original Cap.JPG [ 471.26 KiB | Viewed 1853 times ]
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 Post subject: Re: 4-Wire AC motor W/run cap only
PostPosted: Oct Thu 10, 2019 6:41 pm 
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It seems odd for that old capacitor to have only a "DC volts" rating, but no "AC volts" rating.
For as long as I can remember motor run capacitors are rated for "AC volts." Sometimes there is an additional rating for "DC volts" but not always.
So that one must be a very very old capacitor.

Try a new 4uF capacitor that is rated for motor-run applications. I'm will to bet it will work.

-EB

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 Post subject: Re: 4-Wire AC motor W/run cap only
PostPosted: Oct Thu 17, 2019 11:46 pm 
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electricboyo wrote:
After browsing through a bunch of data for PSC motors, I’ll make an educated guess that the capacitor should be in series with the winding that has the larger DC resistance. And the winding with lower DC resistance goes directly to 120V AC.

The 4uF capacitor must be a “motor run capacitor.” A 4uF capacitor made for a ceiling fan should work OK. Ceiling fans have the same type of motor (PSC - permanent split capacitor).

-EB

EB,

I got a [ceiling fan] capacitor today & seriesed it into the high resistance winding of the EAD motor. The motor started & ran beautifully. Zoom in on the capacitor & pull-chain switch combo and read the specs on the cap. Pulling the switch chain did not effect the motor in any way. It appears that the capacitor is: 5mF/10mF @ 250 VAC. Remember the original capacitor was 600 volts DC.

Jack


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Capacitor Wiring of Fan Motor.JPG
Capacitor Wiring of Fan Motor.JPG [ 527.32 KiB | Viewed 1779 times ]
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 Post subject: Re: 4-Wire AC motor W/run cap only
PostPosted: Oct Fri 18, 2019 12:57 am 
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Ceiling fans usually have 2 separate capacitors. Each performs a different function.

1) A 2-wire capacitor is permanently wired in series with one of the two motor windings. For the sake of clarity I will call this the “capacitor winding.” Typically this winding has a somewhat higher DC resistance. Power is applied directly to the other winding. I will call this the “main winding.” It usually has a somewhat lower DC resistance. This arrangement is identical to the wiring diagram for your vintage motor.

2) The other capacitor, which is often two capacitors in the same case (they could be a 10uF and a 5uF), operates as a speed control. It is connected to the on/off speed control pull chain switch. I believe this is what is in your photo. This speed control capacitor assembly (the switch and one or more capacitors) is connected between the incoming AC “hot” and the junction of capacitor 1 and the “main” motor winding. For high speed the AC power goes straight to the motor. For medium speed a 10uF capacitor is placed in series. For low speed the 5uF capacitor is placed in series.

Note: When there is no load on the motor it will run at full speed regardless of whether the switch is on high, medium, or low.

-EB

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 Post subject: Re: 4-Wire AC motor W/run cap only
PostPosted: Oct Sat 19, 2019 12:53 am 
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So, using the capacitor hook-up arrangement above, after an hour runtime the motor got really hot [melting a hole in the foam pad I had it sitting on]. Question: Could the 5/10mF cap.be too much capacitance for full-time run ? Just can't believe that a motor would be designed to run that hot !

Jack


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 Post subject: Re: 4-Wire AC motor W/run cap only
PostPosted: Oct Sat 19, 2019 7:51 am 
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Jack Cureton wrote:
So, using the capacitor hook-up arrangement above, after an hour runtime the motor got really hot [melting a hole in the foam pad I had it sitting on]. Question: Could the 5/10mF cap.be too much capacitance for full-time run ? Just can't believe that a motor would be designed to run that hot !

Jack
For the “run” capacitor that goes in series with the higher resistance motor winding, you must use the 4uF capacitor as stated on the motor nameplate.

The capacitor with the pull chain switch in your photo is part of a speed control circuit. Depending on which position the pull chain switch is in, the capacitance could be 5uF, 10uF, or 15uF. None of those values are right for your motor. Although if you can determine which position of the pull chain switch corresponds to 5uF, that would be the best you can do with that particular capacitor and speed switch assembly.

And you need an actual wattmeter, such as a Kill-A-Watt. It will measure the actual wattage consumed by the motor, which should be quite low when there is no load on the motor. According to its nameplate the motor current is specified to be 0.30A (300mA). This is the total current for both windings and the capacitor. Usually the VA ( volt-amps) will be larger than the watts. If your current is way higher than 0.3A, then try swapping the windings in relationship to the 4uF capacitor. Maybe it’s the winding with lower DC resistance that should be connected to the 4uF capacitor?

Regarding how hot the motor gets, it was designed to be a fan motor or blower motor. It is expected that it will be cooled by the flow of air from the fan or blower. So if the fan or blower wheel is detached from the motor, then the motor will get very hot if permitted to run for a long time.

-EB

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 Post subject: Re: 4-Wire AC motor W/run cap only
PostPosted: Oct Sat 19, 2019 2:09 pm 
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Location: Long Island NY
That capacitor was likely a paper in oil type. So it would work on AC but at a much lower voltage which is the case here. However, the fact that the motor works with a new capacitor basically proves that the old cap is bad. The replacement really needs to be 4-uF as the nameplate on the motor says. Due to the way the forces created by the windings react internally, either more or less capacitance will change the power angle and reduce the torque of the motor. This may cause more heating.

As for getting hot enough to melt a foam pad, that's too hot! If you were running it with the blower wheel on the shaft as pictured, it is probably overloaded. The wheel was meant to go in a particular housing, and needs to be in that housing in order to present the proper load to the motor. You've no doubt noticed that when a vacuum cleaner hose gets blocked the motor races because there's no load on it with no air flow. Well, the housing partially restricts and focuses the air flow to produce higher pressure but lower volume, so there is less load on the motor when the wheel is in the housing than when it is out in the open air. Without the housing it tries to push maximum air in all directions, rather than a smaller volume of air in one direction. I would put it back together in its housing before attempting to run it again.

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 Post subject: Re: 4-Wire AC motor W/run cap only
PostPosted: Oct Sat 19, 2019 6:54 pm 
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How's this ? - Seriesing a 1.5mF capacitor with the high resistance winding, the motor started & ran beautifully. After an hour run time, the motor warmed up only slightly.


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