Induction motor gone bipolar?

Discussion in 'Electronic Repair' started by David Farber, Jul 10, 2009.

  1. David Farber

    David Farber Guest

    I have an automatic gate which uses a GE 5KH36HN62T motor to open and close
    the gate. The gate intermittently will not open. You can hear the motor buzz
    and it will start moving if given a gentle push. The motor uses a capacitor
    start circuit to get it going. The other fault with the motor is that
    sometimes it turns in the wrong direction. This is my analysis of the
    situation so correct me if I'm wrong. The fact that the motor buzzes and
    will start turning with a gentle assist probably means there is a fault in
    the start circuit. I tested the capacitors and they are ok. So I'm thinking
    the internal motor start switch is sticking open. As far as the motor
    occasionally turning the wrong direction, that too can be attributed to the
    faulty start circuit because not only does the start circuit get the motor
    going from a stopped position, it determines the direction that motor will
    turn. If the load is light enough, the motor now may turn in either
    direction if the start windings are not giving it its initial boost. Does
    this make sense?

    Thanks for your reply.
    --
    David Farber
    David Farber's Service Center
    L.A., CA
     
    David Farber, Jul 10, 2009
    #1
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  2. Bipolar? Lubricate it with lithium grease!
     
    William Sommerwerck, Jul 11, 2009
    #2
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  3. "David Farber" <> writes:

    > I have an automatic gate which uses a GE 5KH36HN62T motor to open and close
    > the gate. The gate intermittently will not open. You can hear the motor buzz
    > and it will start moving if given a gentle push. The motor uses a capacitor
    > start circuit to get it going. The other fault with the motor is that
    > sometimes it turns in the wrong direction. This is my analysis of the
    > situation so correct me if I'm wrong. The fact that the motor buzzes and
    > will start turning with a gentle assist probably means there is a fault in
    > the start circuit. I tested the capacitors and they are ok. So I'm thinking
    > the internal motor start switch is sticking open. As far as the motor
    > occasionally turning the wrong direction, that too can be attributed to the
    > faulty start circuit because not only does the start circuit get the motor
    > going from a stopped position, it determines the direction that motor will
    > turn. If the load is light enough, the motor now may turn in either
    > direction if the start windings are not giving it its initial boost. Does
    > this make sense?


    Probably a bad start cap or a fault in the starting circuit.

    An induction motor without the starging winding energized will do exactly
    as you describe - have no real preference for direction and no starting torque.

    --
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    Samuel M. Goldwasser, Jul 11, 2009
    #3
  4. David Farber

    David Farber Guest

    Samuel M. Goldwasser wrote:
    > "David Farber" <> writes:
    >
    >> I have an automatic gate which uses a GE 5KH36HN62T motor to open
    >> and close the gate. The gate intermittently will not open. You can
    >> hear the motor buzz and it will start moving if given a gentle push.
    >> The motor uses a capacitor start circuit to get it going. The other
    >> fault with the motor is that sometimes it turns in the wrong
    >> direction. This is my analysis of the situation so correct me if I'm
    >> wrong. The fact that the motor buzzes and will start turning with a
    >> gentle assist probably means there is a fault in the start circuit.
    >> I tested the capacitors and they are ok. So I'm thinking the
    >> internal motor start switch is sticking open. As far as the motor
    >> occasionally turning the wrong direction, that too can be attributed
    >> to the faulty start circuit because not only does the start circuit
    >> get the motor going from a stopped position, it determines the
    >> direction that motor will turn. If the load is light enough, the
    >> motor now may turn in either direction if the start windings are not
    >> giving it its initial boost. Does this make sense?

    >
    > Probably a bad start cap or a fault in the starting circuit.
    >
    > An induction motor without the starging winding energized will do
    > exactly
    > as you describe - have no real preference for direction and no
    > starting torque.


    Thanks Sam! That's the answer I was hoping for.

    --
    David Farber
    David Farber's Service Center
    L.A., CA
     
    David Farber, Jul 11, 2009
    #4
  5. David Farber

    David Farber Guest

    Meat Plow wrote:
    > On Fri, 10 Jul 2009 14:54:38 -0700, "David Farber"
    > <>wrote:
    >
    >> I have an automatic gate which uses a GE 5KH36HN62T motor to open
    >> and close the gate. The gate intermittently will not open. You can
    >> hear the motor buzz and it will start moving if given a gentle push.
    >> The motor uses a capacitor start circuit to get it going. The other
    >> fault with the motor is that sometimes it turns in the wrong
    >> direction. This is my analysis of the situation so correct me if I'm
    >> wrong. The fact that the motor buzzes and will start turning with a
    >> gentle assist probably means there is a fault in the start circuit.
    >> I tested the capacitors and they are ok. So I'm thinking the
    >> internal motor start switch is sticking open. As far as the motor
    >> occasionally turning the wrong direction, that too can be attributed
    >> to the faulty start circuit because not only does the start circuit
    >> get the motor going from a stopped position, it determines the
    >> direction that motor will turn. If the load is light enough, the
    >> motor now may turn in either direction if the start windings are not
    >> giving it its initial boost. Does this make sense?
    >>
    >> Thanks for your reply.

    >
    > How did you test the start cap? If it's flaky it's not going to
    > advance the phase to start the motor and could possibly start
    > backwords.


    I tested the caps with my Bob Parker ESR meter. There are two 130uF 330V
    capacitors in parallel. I checked them out of circuit to make sure. I'm
    fairly certain I tested them for shorts because the ESR was very low. I'm
    going to have another visit with the gate this afternoon and specifically
    test out the motor starting circuit.

    Here is a schematic that I drew up a while back. Except for my head
    scratching of what's energizing relay "B", I think the rest of the diagram
    is accurate. It doesn't help that about 75% of the wires are all the same
    color!

    Schematic: http://www.pbase.com/mrfixit/image/81687434
    For other pics of the electronics: http://www.pbase.com/mrfixit/gate

    Thanks for your reply.
    --
    David Farber
    David Farber's Service Center
    L.A., CA
     
    David Farber, Jul 11, 2009
    #5
  6. David Farber

    David Farber Guest

    > "David Farber" <> wrote in message
    > news:4a57b896$0$4078$...
    >> I have an automatic gate which uses a GE 5KH36HN62T motor to open
    >> and close the gate. The gate intermittently will not open. You can
    >> hear the motor buzz and it will start moving if given a gentle push.
    >> The motor uses a capacitor start circuit to get it going. The other
    >> fault with the motor is that sometimes it turns in the wrong
    >> direction. This is my analysis of the situation so correct me if I'm
    >> wrong. The fact that the motor buzzes and will start turning with a
    >> gentle assist probably means there is a fault in the start circuit.
    >> I tested the capacitors and they are ok. So I'm thinking the
    >> internal motor start switch is sticking open. As far as the motor
    >> occasionally turning the wrong direction, that too can be attributed
    >> to the faulty start circuit because not only does the start circuit
    >> get the motor going from a stopped position, it determines the
    >> direction that motor will turn. If the load is light enough, the
    >> motor now may turn in either direction if the start windings are not
    >> giving it its initial boost. Does this make sense? Thanks for your reply.



    Wild_Bill wrote:
    > I didn't get any results by searching the GE number provided, but your
    > description sounds as though the motor is a common capacitor start
    > split-phase AC motor, David.
    >
    > Some of these types of motors have 2 AC capacitors.. a higher value
    > start capacitor (typically over 100uF), and a low value run capacitor
    > (generally under 30uF)
    >
    > The behavior you've described sounds as though there is a fault in
    > the start circuit, as you suspected, and Sam suggested.
    > These motors will exhibit the symptoms you experienced as far as
    > humming when they fail to spin up, but run when the shaft is spun by
    > external means.
    > This type of motor consists of a start capacitor, in series with a
    > start winding, a start/run centrifugal switch, and a run winding.
    > At rest, the start winding (and series capacitor) is connected in
    > parallel with the run winding, by the centrifugal switch.
    >
    > If your motor doesn't include a centrifugal switch, then it's a
    > different type of motor than a split-phase motor.
    >
    > In properly operating capacitor start split-phase motor, when power
    > is applied, the start winding spins up the rotor, the weights of the
    > centrifugal switch overcome the tension of the springs associated
    > with the switch, and the switch opens, allowing the run winding to
    > take over. When the power is removed, the rotor begins to slow, then a
    > distinct
    > click is heard, when the centrifugal mechanism resets as the rotor
    > approaches the lower switch point speed as it continues to coast to a
    > stop.


    Interesting point about the "click." I do here click(s?) when the gate stops
    moving. I had always thought the click was being caused by the mechanical
    movement of the switching relays.

    >
    > These types of motors aren't instantly reversible.

    There is about a 30 second delay before the gate starts to automatically
    close after reaching the fully open positioned. I don't think it is possible
    for the rotor to continue to turn if the gate has stopped unless there is
    some intermediate transmission in the motor itself.

    If for some reason
    > power is re-applied before the rotor stops (not the usual start/stop
    > procedure), the motor will continue to run in the same direction the
    > rotor was coasting. This is a characteristic of these motors, in that
    > the rotor needs to stop before power is re-applied. This is important
    > for applications where the motor is wired to be reversible.
    >
    > For visual inspection, you'll want to examine the areas of the shaft
    > where the bearings are situated in the case of sleeve bearings. If
    > the sleeve bearings are worn, the motor may have to be replaced, as
    > these aren't usually a service part.
    > When the sleeve bearings are badly worn, it may be noticable by
    > looking for signs that the rotor has been contacting/rubbing on the
    > sectors of the stator.
    >
    > Another important component is the centrifugal switch. If the
    > contacts are badly pitted and/or burnt from arcing, the switch should
    > be replaced (if it's available as service part). Some folks are
    > comfortable with filing or dressing the contacts with abrasives
    > (emery or sandpaper), then burnishing the contacts.


    If it is the centrifugal switch, I'm hoping it easy to remove and replace.
    What are the chances of that happening?

    > If the contacts' connection has become high in resistance due to
    > pitting from arcing, the motor could fail to spin up in the way
    > you've described.
    > When these motors fail to spin up, a very likely cause is the start
    > capacitor.
    > Depending upon what type of tester was used, the results indicated
    > when testing AC capacitors may be inconclusive as to the quality of
    > the capacitor.
    > Testing the motor with a new AC capacitor is a better approach.
    >
    > If a fault has developed within the start winding of the motor, the
    > motor will most likely have to be replaced.


    I think the easiest and most telling test will be to hook up an ohm meter
    between the two start windings and see if there is continuity, then go from
    there.

    >
    >

    Hi WB,

    You're right about the two capacitors. However they are wired in parallel in
    this situation. Since I am not the original service guy on the gate, perhaps
    it's not supposed to be that way. Here is the wiring diagram that I drew
    from tracing out the connections.
    http://www.pbase.com/mrfixit/image/81687434

    Thanks for your reply.
    --
    David Farber
    David Farber's Service Center
    L.A., CA
     
    David Farber, Jul 11, 2009
    #6
  7. David Farber

    Jamie Guest

    David Farber wrote:

    > I have an automatic gate which uses a GE 5KH36HN62T motor to open and close
    > the gate. The gate intermittently will not open. You can hear the motor buzz
    > and it will start moving if given a gentle push. The motor uses a capacitor
    > start circuit to get it going. The other fault with the motor is that
    > sometimes it turns in the wrong direction. This is my analysis of the
    > situation so correct me if I'm wrong. The fact that the motor buzzes and
    > will start turning with a gentle assist probably means there is a fault in
    > the start circuit. I tested the capacitors and they are ok. So I'm thinking
    > the internal motor start switch is sticking open. As far as the motor
    > occasionally turning the wrong direction, that too can be attributed to the
    > faulty start circuit because not only does the start circuit get the motor
    > going from a stopped position, it determines the direction that motor will
    > turn. If the load is light enough, the motor now may turn in either
    > direction if the start windings are not giving it its initial boost. Does
    > this make sense?


    Yes
    check the centrifugal switch.
     
    Jamie, Jul 12, 2009
    #7
  8. David Farber

    Jamie Guest

    David Farber wrote:

    > Meat Plow wrote:
    >
    >>On Fri, 10 Jul 2009 14:54:38 -0700, "David Farber"
    >><>wrote:
    >>
    >>
    >>>I have an automatic gate which uses a GE 5KH36HN62T motor to open
    >>>and close the gate. The gate intermittently will not open. You can
    >>>hear the motor buzz and it will start moving if given a gentle push.
    >>>The motor uses a capacitor start circuit to get it going. The other
    >>>fault with the motor is that sometimes it turns in the wrong
    >>>direction. This is my analysis of the situation so correct me if I'm
    >>>wrong. The fact that the motor buzzes and will start turning with a
    >>>gentle assist probably means there is a fault in the start circuit.
    >>>I tested the capacitors and they are ok. So I'm thinking the
    >>>internal motor start switch is sticking open. As far as the motor
    >>>occasionally turning the wrong direction, that too can be attributed
    >>>to the faulty start circuit because not only does the start circuit
    >>>get the motor going from a stopped position, it determines the
    >>>direction that motor will turn. If the load is light enough, the
    >>>motor now may turn in either direction if the start windings are not
    >>>giving it its initial boost. Does this make sense?
    >>>
    >>>Thanks for your reply.

    >>
    >>How did you test the start cap? If it's flaky it's not going to
    >>advance the phase to start the motor and could possibly start
    >>backwords.

    >
    >
    > I tested the caps with my Bob Parker ESR meter. There are two 130uF 330V
    > capacitors in parallel. I checked them out of circuit to make sure. I'm
    > fairly certain I tested them for shorts because the ESR was very low. I'm
    > going to have another visit with the gate this afternoon and specifically
    > test out the motor starting circuit.

    ESR meter isn't telling you the full story...
    You need to know the Farad value..
    ESR is not a factor here.
     
    Jamie, Jul 12, 2009
    #8
  9. David Farber

    David Farber Guest

    > "David Farber" <> wrote in message
    > news:4a58d6b9$1$9366$...
    >>
    >> Interesting point about the "click." I do here click(s?) when the
    >> gate stops
    >> moving. I had always thought the click was being caused by the
    >> mechanical movement of the switching relays.
    >>
    >>>
    >>> These types of motors aren't instantly reversible.

    >> There is about a 30 second delay before the gate starts to
    >> automatically close after reaching the fully open positioned. I
    >> don't think it is possible
    >> for the rotor to continue to turn if the gate has stopped unless
    >> there is some intermediate transmission in the motor itself.
    >>
    >>
    >> If it is the centrifugal switch, I'm hoping it easy to remove and
    >> replace. What are the chances of that happening?
    >>
    >>>
    >>> If a fault has developed within the start winding of the motor, the
    >>> motor will most likely have to be replaced.

    >>
    >> I think the easiest and most telling test will be to hook up an ohm
    >> meter between the two start windings and see if there is continuity,
    >> then go from
    >> there.
    >>
    >>>
    >>>

    >> Hi WB,
    >>
    >> You're right about the two capacitors. However they are wired in
    >> parallel in
    >> this situation. Since I am not the original service guy on the gate,
    >> perhaps
    >> it's not supposed to be that way. Here is the wiring diagram that I
    >> drew from tracing out the connections.
    >> http://www.pbase.com/mrfixit/image/81687434
    >>
    >> Thanks for your reply.



    Wild_Bill wrote:
    > Hi David, I think I should've mentioned that my motor comments were
    > related to testing a motor that's been isolated from any controls, as
    > in bench testing.
    > Bench testing would be where the click of the centrifugal switch
    > mechanism would be very noticeable.
    >
    > I dunno if the motor in the gate controller is a typical motor, or a
    > special-purpose motor built for this particular appliance (custom
    > built for the OEM/gate control company's specific requirements). If
    > all of the switching circuitry is separate from the motor, then it's
    > probably a typical motor.
    > Typical meaning that the internal switches in the motor would just be
    > the centrifugal switch, and a thermal protection device.
    >
    > Testing the controls (wuuf! that's a lot of contacts) may be
    > simplified by placing test lamps at the motor connector, instead of
    > the motor. Light duty test lamps won't absolutely confirm that the main
    > contactor for the motor is capable of passing the motor's required
    > current, but the lamps should indicate that the basic open and close
    > functions are taking place. There are probably some devices (possibly
    > a single device) that act as travel limit switches for the gate
    > arm/linkage.
    > So, I would suspect that if you place lamps where the motor would be,
    > when you select Open, the one lamp would be on until you give the
    > controller the limit signal (it's open, so stop).
    > Then if I understand, the controller delay will cause a pause before
    > the controller will auto-cycle to Close, so the other lamp should
    > light until you give the controller the limit signal (it's closed, so
    > stop).
    > Starting these types of motors repeatedly is severe duty for the start
    > windings and the start capacitor(s). What I mean by repeatedly would
    > be the motor starting more than 6 or 8 times per hour. And since each
    > opening is actually starting the motor twice, using test lamps for
    > testing may be a good idea.
    > If you had some heavier loads (6 to 10A) to substitute the motor
    > with, that would be more of an actual test of the controller, as the
    > motor will draw some serious current very briefly each time it starts.
    >
    > Typically, the centrifugal switch for the start winding is located in
    > the end bell of the motor opposite the output shaft end (usually the
    > end where the leads enter the motor).
    > The switch contacts are generally secured to the end bell of the
    > motor.
    > Removing the end bell of a general purpose utility-type motor usually
    > means removing the nuts from four long screws that secure the end
    > bells and center (stator section) together, by running thru the case
    > with screw heads at one end, and nuts at the other.
    > It's always a good idea to mark the orientation of the end bells to
    > the case by making distinct marks at both ends of the case and the
    > end bells, where the end bells meet the case.
    >
    > Maybe Bob Parker would know the specific differences, but I believe
    > that the characteristics of AC capacitors used in induction motors
    > are significantly different than electrolytic capacitors typically
    > found in electronic equipment.
    >
    > Other signs to look for in this type of unit would be discolored
    > terminals on wiring connections, which generally always indicates
    > high resistance connections that have overheated.
    >
    >


    I had another look at the motor and mechanism this afternoon. The motor
    start ciruit measured open. Whether it's the centrifugal switch or it's the
    start winding, it needs repair. As for right now, I'm going to call some
    local motor repair shops next and see if it can be fixed. I like the idea
    have having an experienced person look at it and not having to worry about
    for another 30 years. The capacitors look ok physically. No swelling,
    cracking, or discoloration. The relays show a tiny bit of wear but nothing
    too bad.

    Thanks for your reply.
    --
    David Farber
    David Farber's Service Center
    L.A., CA
     
    David Farber, Jul 12, 2009
    #9
  10. David Farber

    David Farber Guest

    "Meat Plow" <> wrote in message
    news:...
    > On Sat, 11 Jul 2009 11:13:51 -0700, "David Farber"
    > <>wrote:
    >
    >>Meat Plow wrote:
    >>> On Fri, 10 Jul 2009 14:54:38 -0700, "David Farber"
    >>> <>wrote:
    >>>
    >>>> I have an automatic gate which uses a GE 5KH36HN62T motor to open
    >>>> and close the gate. The gate intermittently will not open. You can
    >>>> hear the motor buzz and it will start moving if given a gentle push.
    >>>> The motor uses a capacitor start circuit to get it going. The other
    >>>> fault with the motor is that sometimes it turns in the wrong
    >>>> direction. This is my analysis of the situation so correct me if I'm
    >>>> wrong. The fact that the motor buzzes and will start turning with a
    >>>> gentle assist probably means there is a fault in the start circuit.
    >>>> I tested the capacitors and they are ok. So I'm thinking the
    >>>> internal motor start switch is sticking open. As far as the motor
    >>>> occasionally turning the wrong direction, that too can be attributed
    >>>> to the faulty start circuit because not only does the start circuit
    >>>> get the motor going from a stopped position, it determines the
    >>>> direction that motor will turn. If the load is light enough, the
    >>>> motor now may turn in either direction if the start windings are not
    >>>> giving it its initial boost. Does this make sense?
    >>>>
    >>>> Thanks for your reply.
    >>>
    >>> How did you test the start cap? If it's flaky it's not going to
    >>> advance the phase to start the motor and could possibly start
    >>> backwords.

    >>
    >>I tested the caps with my Bob Parker ESR meter. There are two 130uF 330V
    >>capacitors in parallel. I checked them out of circuit to make sure. I'm
    >>fairly certain I tested them for shorts because the ESR was very low. I'm
    >>going to have another visit with the gate this afternoon and specifically
    >>test out the motor starting circuit.
    >>
    >>Here is a schematic that I drew up a while back. Except for my head
    >>scratching of what's energizing relay "B", I think the rest of the diagram
    >>is accurate. It doesn't help that about 75% of the wires are all the same
    >>color!
    >>
    >>Schematic: http://www.pbase.com/mrfixit/image/81687434
    >>For other pics of the electronics: http://www.pbase.com/mrfixit/gate
    >>
    >>Thanks for your reply.

    >
    > It's not rocket science. It's a GE fractional horsepower induction
    > motor. If the start cap is ok then the mechanical switching inside the
    > motor is bad. And I don't recall ever seeing the need to parallel two
    > 130's together to get a 1/6 HP motor to start. Maybe one for run and
    > one for start but usually smaller value for the run cap. Find a
    > drawing for the motor.


    Here are some additional specs I found on the motor label:

    1/3 hp

    Von Weise Gear Co., St. Louis, Missouri
    Model V00358AG10
    6 (six!) rpm.

    Time Rating: cont.

    I still cannot find any info regarding what value capacitor should be
    installed with this motor. The motor with pulley and case weighs 30 pounds.
    I saw a hefty spring inside the casing via an air vent near the bottom.

    Thanks for your reply.

    --
    David Farber
    David Farber's Service Center
    L.A., CA
     
    David Farber, Jul 13, 2009
    #10
  11. David Farber

    David Farber Guest

    > "David Farber" <> wrote in message
    > news:4a5a829e$0$8678$...
    >>
    >> Here are some additional specs I found on the motor label:
    >>
    >> 1/3 hp
    >>
    >> Von Weise Gear Co., St. Louis, Missouri
    >> Model V00358AG10
    >> 6 (six!) rpm.
    >>
    >> Time Rating: cont.
    >>
    >> I still cannot find any info regarding what value capacitor should be
    >> installed with this motor. The motor with pulley and case weighs 30
    >> pounds.
    >> I saw a hefty spring inside the casing via an air vent near the
    >> bottom.
    >>
    >> Thanks for your reply.
    >>


    Wild_Bill wrote:
    > I was wondering earlier, if the motor was a gearhead motor. With an
    > output of 6 RPM, there wouldn't definitely be a need for high
    > starting torque for the motor shaft, since the geartrain provides
    > output shaft torque.
    >
    > So, the capacitors that were found may not be the original ones, and
    > are not likely to be for a 1/6 HP motor.
    > The motor shop where I get parts told me that a general guideline for
    > start capacitor (value) sizing is 500uF for 1 HP, for capacitor start
    > split-phase motors.
    > The capacitor value you found would be adequate for a capacitor start
    > split-phase motor of 3/4 HP to 1 HP.
    > Anything is possible with used equipment, and if the capacitor had
    > failed in the past, someone may have confused the
    > resistors-in-parallel rule, with capacitors in parallel.
    >
    > Since the gear reduction unit provides a considerable amount of
    > torque, it's possible that the motor may be a PSC permanent split
    > capacitor type, and not a capaitor start split-phase motor.
    >
    > The capacitor value would still be wrong for a PSC motor that size.
    > PSC motors are often used with gear reduction boxes to provide low
    > RPM outputs, but the capacitors used are very low values, as in
    > single or double-digit values, not 100+uF.
    >
    > PSC motors are fairly simple, in that the stator is made up of two
    > identical windings in series, with the 3 terminals arranged like a
    > center-tapped transformer winding.
    > The connection of one of the capacitor's leads is changed for CW or
    > CCW rotation.
    >
    > Commercial application PSC motors are very reliable, they often have
    > ball bearings for the motor shaft, and nearly always have internal
    > thermal protection, and they are commonly designed with impedance
    > protection.
    >
    > The PSC types don't have centrifugal switches, and the spring you saw
    > thru the vent is likely to be part of the mechanism for a centrifugal
    > switch.
    >
    >

    Just to update what I found out in the past few days: The label on the motor
    says 1/3 hp. I called some repair shops and asked if they knew about the
    start capacitance value. One tech told me that the GE 5KH series was a split
    phase motor and did not require any start capacitor. I finally found a local
    guy who was able to come to my shop and call me back with an estimate. He
    said the aluminum start windings were bad and that he would replace both the
    start and run windings with copper wires. As to the question of starting
    capacitance, he said adding a capacitor wouldn't hurt especially if it was
    running that way for a long time. I'll be getting the repaired motor back
    tomorrow and hopefully it will be as good as new.

    Thanks for your reply.
    --
    David Farber
    David Farber's Service Center
    L.A., CA
     
    David Farber, Jul 18, 2009
    #11
  12. David Farber

    David Farber Guest

    >
    > "David Farber" <> wrote in message
    > news:O788m.51973$...
    >>>

    >> Just to update what I found out in the past few days: The label on
    >> the motor
    >> says 1/3 hp. I called some repair shops and asked if they knew about
    >> the start capacitance value. One tech told me that the GE 5KH series
    >> was a split
    >> phase motor and did not require any start capacitor. I finally found
    >> a local
    >> guy who was able to come to my shop and call me back with an
    >> estimate. He said the aluminum start windings were bad and that he
    >> would replace both the
    >> start and run windings with copper wires. As to the question of
    >> starting capacitance, he said adding a capacitor wouldn't hurt
    >> especially if it was running that way for a long time. I'll be
    >> getting the repaired motor back tomorrow and hopefully it will be as
    >> good as new.


    Wild_Bill wrote:
    > I'm glad you found a solution, David. From what I've been hearing in
    > recent years, shops that are interested in repairing small motors are
    > becoming scarce.
    >
    > I realized that I'd mis-stated the HP rating you stated from the
    > motor label after the reply was sent. Still, that value of
    > capacitance is excessively high for a small motor.
    >
    > The guy that said a split-phase motor doesn't require a start
    > capacitor is correct, although when S-P motors are manufactured with
    > a start capacitor, they're capable of being used in applications that
    > require higher starting torques, hence the CS,S-P naming.
    > Many heavy duty motor applications, such as industrial-duty air
    > compressors require motors with both start and run capacitors..
    > CS,CR,S-P type.
    > Because of the high gear ratio to attain the 6 RPM output, the
    > starting torque requirement wouldn't be very high. The ratio is over
    > 250:1 for a 1700 RPM motor.
    >


    I got a reply from Regal Beloit regarding my wiring inquiry. I've uploaded
    the diagram here:
    http://members.dslextreme.com/users/farberbear/GE_motor/Motor-wiring.jpg

    Interestingly enough, in the reply from the support representative, he said
    that this motor does not require a capacitor nor is it likely it will
    operate if one is used. So why is there a capacitor drawn in the diagram?

    By the way, I reinstalled the repaired motor exactly the way it was
    previously installed, with the two capacitors, and it is working fine.

    --
    David Farber
    David Farber's Service Center
    L.A., CA
     
    David Farber, Jul 22, 2009
    #12
  13. David Farber

    David Lesher Guest

    "Wild_Bill" <> writes:


    >In properly operating capacitor start split-phase motor, when power is
    >applied, the start winding spins up the rotor, the weights of the
    >centrifugal switch overcome the tension of the springs associated with the
    >switch, and the switch opens, allowing the run winding to take over.



    I'll take exception to one part of Bill's otherwise great wording....

    As you can see in the diagram linked in this thread; the running winding
    is always on [...when the motor is powered up, obviously...] but the
    starting winding is soon turned off.

    The starting winding is on only for the ~~~100-200 ms it takes the motor to
    spin up. (I measured the time once in Machines Lab. Hi Prof Klingshirn!)

    (You can work all this out with copious amounts of math but the following
    will do.)

    What makes it all work is phase shift, both electrical and physical.
    The starting winding jerks the motor shaft slightly, then 90 degrees
    later [electrically] the running winding [offset physically around the
    path of the rotor] follows up with a second one. That one-two punch is
    what starts the motor in the correct direction. If you want to go the
    other way, flip the running winding around so the running jerk is the
    opposite side of the starting peak.

    The capacitor also limits the starting current to some finite value;
    more capacitance in parallel is more current. Since it's used for only
    200 ms, the starting winding can get away with much higher current
    than the running one. But hold the motor stalled; and smoke will soon
    arise...unless the breaker trips.

    Now a shaded pole motor fudges in the phase shift without a cap, but
    gives far less torque. If you recall analog electric clocks; that's what
    they use.

    Three phase makes it all trivial. You get 3 peaks for the three windings,
    each peak offset by 120 degrees [electrically] and the winding offset by
    120 degrees physically; so you get ABCABCABCABC and the motor needs no
    starting winding nonsense at all....it just goes.
    --
    A host is a host from coast to
    & no one will talk to a host that's close........[v].(301) 56-LINUX
    Unless the host (that isn't close).........................pob 1433
    is busy, hung or dead....................................20915-1433
     
    David Lesher, Aug 4, 2009
    #13
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