Split Phase Induction Motors

Discussion in 'General Electronics Chat' started by R!f@@, Dec 11, 2012.

  1. R!f@@

    Thread Starter AAC Fanatic!

    Apr 2, 2009
    I am no Motor Repair Genius but I can very well figure out how a connection is made and if it is wrong.

    You know that I am have been fixing the FSM petrol pumps and anything and everything related to electronic to electric and even to sometimes mechanic [ In mechanics, I have to first figure out how the friggin thing works in order to fix it]

    They are warned not to call me unless they have no other choice. Cause then I can squeeze them dry :D.

    And the best part is they know that,and yet they destroy the thing almost completely by their techs or another low class electrician who just has the basic know how in household wiring. Don't u just think it is great here.

    { I think it's about time them Gilberco guys train me as a certified guy in Maldives. Don't u think ?}

    Story time.

    Now these Motors are HVAC motors [ I dunno what tht means but I have figured tht it is some what air leak proof or something as the motor is used in Petrol Vapor involved areas]. It is labelled Explosion proof, and all those fancy safety working level things. So to say this bugger is pretty expensive since it's operation safety concerns human lives.

    The Motor is made by Franklin Electric.
    Rated at 3/4 HP, 220VAC, around 1500rpm, continues operation.
    And is a capacitor Start, Capacitor Run motor, with a centrifugal switch inside.

    A few weeks ago one motor stalled.They have been trying to get one repaired together with a local tech for quite sometime. The centrifugal switch was totally destroyed, I dunno when tht happened. It may have been during the operation or it might have been while they dismantled it, as the wiring are pretty tight and any open holes where the wire comes out are filled with epoxy. All in all more work for me with higher pay checks :D

    I bet the tech gave up and did not pick up their call so they called me. The Evil genius.

    A couple of motors were there. Nothing works, no center switches and no good capacitors. And the capacitor they had are just too darn huge to go into the housing of the motor. And they were planning to put some sorta timer to cut the start cap when the motor picks up speed. The caps were now planned to be mounted else where inside the termination box which the SS relay and the wire terminations are. It will be safe since all the motor and box plus wiring are housed in metal. Even the wire that comes from the motor to termination box is contained with in a steal pipe.

    Then I did not know the caps were supposed to be inside the motor end caps. Cause when I saw it, two caps were already outside the motor. So Naturally I figured they will be outside since I have seen them. But I never new 'em Gilberco guys had put the caps inside. And this turned out to be pretty bad assumption from my side. I made a mistake in trusting them techs. I should have known better. Sigh ! :(

    Something must have been done way before I got involved with a motor, I say this cause this is my first attempt in fixing one. Before I never got to touch a motor besides the electronics.
    So the problem was [which I assumed], since the motor field wiring , center switch,thermal cut out and the caps are made inside the motor, there were only three wires coming out. They forced the thing open, broke the wires and all hell got loose. So now they had no idea which freakin wire goes where. Since the caps are located at both ends, one at the back and the other one on the end. Wires were going in side the field which actually has no connection to the coil. So this made the job a whole lot more confusing to them.

    They cut off the wire took the cap out made some sorta connection I really have no idea about put the new caps outside {since the old ones didn't work} and ran the motor fro some time and gave up.

    So to say I am not sure about the history of these things.
    From now I will tell you what I saw and did.

    So from this point is what actually went on after they called me.

    I went to there workshop and they wanted me to get the motor running.What I first saw was a Franklin Motor which has so many wires coming out { I never new then it is not how it shud be}

    But they had two types of Motors. One that came with the pump and other two made from china. I dunno what they call them, to me it sounded like wooo yung chin chon motor or somethin. The label says in box Chinese letters, so I called them wooyun motor :D and the other one Gilberco. Now I can identify them seperate

    They both were almost the same but the wooyun turned the wrong way which is CW. The Gilberco ones were CCW. They have destroyed two of them center switches while trying to figure out how to turn them CCW . And these wooyun's were totally brand new.I can see from the fresh paint it has.
    They cannot get it running either way now, so now they planned to fix the gilberco one and a local tech has bought some new caps. A 300μf one and two 20uf ones (this was the biggest mistake in the first place. U will know later) PLUS A TIMER. The new guys plan were to use the timer instead of the centrifugal switch.

    "I was wondering how a uneducated tech who has no freakin knowledge on induction motor what so ever gonna time a freakin timer to cutoff at the right rpm with out a tacho

    I like totally blanked staring the office guy. "What in god's name were u trying to do? ", I asked even though I knew he cannot answer. I just had to ask.

    I was LMAOF

    Continued on post # 4.
    Last edited: Dec 11, 2012
  2. Dodgydave

    Distinguished Member

    Jun 22, 2012
  3. Meixner


    Sep 26, 2011
    I worked with some Gilbarco engineers once, they were very hard to please.
  4. R!f@@

    Thread Starter AAC Fanatic!

    Apr 2, 2009
    well, what happened happened.

    They needed me to fix one ASAP and the two wooyun's later.
    Everything was transferred to my work shop.

    I started to work on the motors and I had a tough time to figure out the field connection. I was like at it for hours, going through the net, googling, reading everything related to these kind of motors. I was saving pdf's. going through them again and again.

    But I never got any info on the capacitor values used in the Gilberco ones. All I got were average values like for a starting cap it would around 300μf & for the runnin it would be lower like 30 to 50μ. Which lead me to false assumptions. Cause they had too bought new caps. One 300μf & two 10μf

    From this I too naturally figured tht the starting is the 300 and running is 20uf, two 10μf's in parallel. From the size of it I know it will never go inside the motor and to make things worse they never told me tht there were caps inside the Gilberco to begin with.

    It took me like 6 hours to study the bloody thing. And since the motor is used in petrol pumps I need to make sure tht what I do will not cause a fire hazard. Since the two caps were located inside the termination box and it is sealed from vapor it will be safe ( actually they both should be inside the motor which I never knew)

    After blowing a couple of fuses and tripping the MCB few times I manged to start the motor and got it running smoothly anti clockwise. I managed to get the cetrifugal switch working and tested it by manually rotating the motor coupled to a drill. The swich opens every time at a given rpm. Which tells me there is nothing wrong with the switch ( actually I manged to put one together from other few broken ones I brought from there workshop. hee hee hee).

    My findings about the Gilberco Motor

    Everything I know is totally from studying the motor and comparing to the pdf's I got from the web.

    It has two running windings, one start winding, one centrifugal switch, one thermal overload cutoff and one LV HV switch.

    None of them had any connection when I first saw them what soooooooooooooo ever.!:eek:.

    I bet u know I had to rewire the whole thing properly. But I won't be needing the LV (low voltage switch) LV is for 115VAC & HV is for 220VAC.

    Logic tells me that HV connection, the running winding should be in series.
    And I did a winding leakage test with the megger and all went A-OK. Besides most of the pdf's says they will be in series.

    I made all the connections, thermal overload and tested the motor, left the LV/HV switch as I don't need it here. The motor has some heavy starting torque. It would jump and then start. I can hear the center switch kicking in. Measured the current and all is well with in the stated range. I labeled the wires so even a n00b can connect the caps correctly. Still I showed them techs (an Indian guy) how to connect caps and ran the motor smoothly.

    So all is well. I got me hefty pay check and I was done for the month.

    Two days later the guy called and yelled the motor exploded. What he meant was the starting cap exploded inside the termination box and the power went out from the whole gas station.


    I thanked god that no fire had started. He brought the caps and yes the 300μf one was like hot dog :D. I was like, what the hell.? It was a good cap and I tested it. Rated at 275VAC, but I dunno it was explosion proof or not cause I did not buy it, they did, so I was clean. (grin)

    I mean hey, c'mon. I ran the motor with that cap for a for a few hours so it was not my problem.

    This time I did not want to get involved in something as little as a motor cap problem. So they found some new caps from somewhere,(new or old I dunno) installed them ran it for a day or so when what was to happen happened.

    This time something definitely shorted. Pooof! power went out. too much smoke. heeheehee !
    The caps blew again. He called and I said it is not my problem since I tested the motor in front of them it is not a motor fault. Them techs are messing up the connections and I am not gonna do anything since they are complaining about my service charges. They complained that my price is same as that of a new motor. So I said "go and buy a f*****G motor and quit calling me."......click.!

    in the mean time
    They have no way to run it..no caps available in Maldives ( again ). But I managed to find from my sources but it cost me MVR 1600.00 and they were too damn big. They were like 1 foot long. How the hell am I gonna put them in square inch box. Having no option I gave them and they obviously rejected saying they cannot let them hang loose in the open.

    Crap ! what total loss.! thousand bucks down the drain. :mad:

    One problem that I am facing these times in Maldives is like the forbidden topic., the over throwing of the democratic president and cutting the funds from all the government offices and since fuel supply is government owned they are having a hard time getting the budget. Everything happens because of that no good president we have. I know I am not suppose to write anything about them in AAC but WTF am I suppose to do.. tell me.!
    Stop...!Sorry Bill & Geo.... back to work.

    After that they again said they will get them new motors.

    Next day...ring ring...I was fast asleep when the phone rang.
    They wanted me fix the (our coming neighbor, not the Indians) Chinese woooooooooooooooyun motor. I said Ill do what I can and the charges will be lower too since no company has enough budget due to them barbarians gobbling all the money into their pockets..............oooops! Sorry. !!!

    I took them apart and guess what to my surprise, them wooyuns motor's have capacitors inside the friggin motor and yet there were soooooo many wires coming out. It got 3 caps. two 10μf's in parallel and one 88μf. Yes one 88μf not a 300μf. I dunno why I keep telling myself tht. :confused: They messed with these wiring too since the center switch is kaput.

    Below are the Chinese motor caps


    See them good ones...huraaaaaaaaaay ! I got working capacitors. but no working centrifugal switch. Darn it !

    Seeing how the caps were clamped inside it hit me. The Gilbarco motor end housing some what similar spacing and both end had a clamp. Like in the Chinese ones.

    Now I realized that Gilbarco had caps and they should be inside the motor not in the termination box which when I first saw was that the caps are outside, which led me to believe tht they should be outside. Boy I made a huge mistake here. . They have been doing this for a long time I guess. But how did they end up with a 300μf start cap is still a mystery...
    like to remind you that all these **** is going thru my mind....
    Now since I got me good caps I can work with the Gilbarco motor.

    I called and explained the confusion findings and all tht and they too agreed to what I said. I thought may be I can run the Gilbarco with the wooyun caps..no?

    And since they again messed up the wiring I told them to bring the Gilbarco motor which I fixed before. I need to see if it would work. Problem I had was the Start capacitance. 88μf instead of a 300μf. ( mind u tht the 300 was something they gave me, it was never the original value to begin with)

    So. Motor came Took it apart and presto !

    Last edited: Dec 11, 2012
  5. shortbus

    AAC Fanatic!

    Sep 30, 2009
    Think you'll find that the cap voltage was too low.:) Most caps for a 220V motor are in the 375-400 volt range. A 250 -275 volt cap is used on a 110volt motor.
  6. R!f@@

    Thread Starter AAC Fanatic!

    Apr 2, 2009

    I believe the start winding is ashed as u can see from the picture. The 300μ blew and yet they never checked the motor but put another cap and ran it to it's grave.

    See the lamination. Part of the core has been forced to a side but I cannot see any damage on the rotor. What could have caused it.

    Since the two brand are way different I cannot switch the rotor. So I had them brought in another wasted Gilbarco field and take a look at it


    I like to know from the more experienced ones. Will the core work in the long run. What would be the effect on the motor rpm and current. ?

    I did a test on the resistance with a mili ohm meter and there is no short for sure. And I did another test using the Megger to check if any leakage is there from coil to the core. HV check passed. No leaks what so ever in the above field.
  7. BillB3857

    Senior Member

    Feb 28, 2009
    Somewhere along the line, it looks like somebody has done a mix and match between motors. There is no way the stator laminations can show that much damage without marking the rotor. Bad bearings can cause a rotor to rotate off center enough to drag the stator and cause that kind of damage.
  8. R!f@@

    Thread Starter AAC Fanatic!

    Apr 2, 2009
    U know what, I think u are right.
    My q, is that will the second one work ?
  9. R!f@@

    Thread Starter AAC Fanatic!

    Apr 2, 2009
    All the dismantling showed tht the Gilbarco had Caps inside the motor but question was what were there sizes.

    I argued them for a long time and in the end they brought another Gilbarco Motor end WITH the capacitor.

    These were what was inside and these are the ones they been running them motors with..................


    PS : these two caps were at both end caps, one in each. The wire termination with U lugs tells me that one was near the center switch and the other was on the other end as it has long wires that ran from one end to the other.

    Tell me, some one, is Gilbarco using the same capacitance to start and run the motor + to mess things up why are the caps rated at 125VAC ...and NOT... 250VAC or more.

    They were using them at 220VAC mains voltage.


    Take a look at the voltage ratings plus the cap values and somebody please tell me what is going on in here for God's sake.

    I mean 125VAC as a running cap same as the starting cap. The same freakin capacitance. I know they should be different or am I being coned here.

    They made me put a 300μf start cap in a Gilbarco and it start, and ran for like 15 seconds and stop for another 15 sec and start and run for another 20 sec and it went on the whole freakin day as the people came to fill their gas tanks and it was too much for the start winding.

    Tell me I am wrong here...! pleeeeeeeeeeeeeeease somebody...!
    Last edited: Dec 11, 2012
  10. R!f@@

    Thread Starter AAC Fanatic!

    Apr 2, 2009
  11. R!f@@

    Thread Starter AAC Fanatic!

    Apr 2, 2009
    Is it that the values are wrong ?

    Or could it be that the caps actually never see 220VAC, since the caps are never across the supply but always in series with start coil. Both caps have a common connection which I believe connects to start winding .....wait a minute.
    spark8217 likes this.
  12. debe

    Well-Known Member

    Sep 21, 2010
    On 240 V motors the capacitor voltage should be around 400V AC. The run capacitor is rated for continous use & the start is only intermitent rating. The size (value ) of the caps are worked out by the manufacturer for each particular motor (usualy on the motor spec plate). Wrong values will result in posible windings burnout, motor not getting up to speed. To reverse the motor direction just swap the start winding polarity. HVAC is Heating Ventilation And Cooling acronym. Your motor with 2 run windings is posibly for in series for 240V & parallel for 110V. Pic is what i suspect is the basic circuit of the motor.
    R!f@@ and shortbus like this.
  13. tinkerman


    Jul 22, 2012
    Is the motor dual voltage 120/240? Then the starting winding probably connected across 1/2 the main windings (at the center tap). The two run windings are 120 volt each, connected in series for 240 volt. All the windings are 120 volt IOW. And usually the run cap connects directly. It isn't switched.
    R!f@@ likes this.
  14. R!f@@

    Thread Starter AAC Fanatic!

    Apr 2, 2009
    This is how I wired the thing in the first place.
    And it worked until somehow they manage to burn the stator to a crisp.

    My thoughts exactly :D

    @ debe
    So what I did was I extended all the wires in the Gilbarco stator put the thing back with the previous rotor. So now nothing is inside. No caps, no center sw.
    All the wires are out side so I can test it. But It won't run and I kept tripping the CB. And the rotor is not so smooth to turn free hand. I figured the shaft is bend or the bearings are worn out.

    Next I tried the same technique with the wooyun. Put the thing back and this motor rotor is smooth when turned by hand.

    I connected the original capacitors tht came with the motor as per the diagram debe showed, which I came up before during my research. This one tried to turn but did not and it did not trip the breaker, so I figured it must be the start cap timing. I disconnect the cap too soon it stalled. So I kept the start cap connected a bit longer until the motor picks up speed which is like 500ms or so ( even this period is a bit too long) and this time the motor rotates normally.

    I checked the running current and it was around 2.46Amps stable. The motor took off from the bench completely :eek: when is tarts and this happened with the previous Gilbarco and it's running current was around 4Amps as I recall. So I figured the starting torque would jump an unmounted motor clear of the bench.

    The wooyun motor gives a bit of vibration and it would slowly run walk across the bench as it ran. The motor rotated CW, so I switched the run winding at it gave a CCW rotation. :D.

    The center switch timing needs to be accurate for the motor to pick up speed. Since the center switch mechanism is broke I cannot make it to run. I figured then a timer would actually work but with some draw back in the long run. If the timer can be adjusted accurate enough the motor would survive short term start/stop sequence.

    I measured the voltage across the running cap and it was at 400VAC. (thanks debe for clearing this out)

    Does this mean that caps in the Gilbarco are rated at wrong voltage?
    I believe it so.

    And would a timer can actually be used to time the run cap?

    I tried with a relay to disconnect the cap and it was a bit too soon and the motor would stall. Since the relay energises too soon disconencting the cap before the motor starts.

    Next is to built a timer and see if it works :cool:
  15. tinkerman


    Jul 22, 2012
    Timing relay is not the way to go. Sometimes a relay is used to drop out when the voltage reaches a certain level. Start windings need to be energized until the motor reaches about 75% of full speed. Another method used is a current sense where the relay drops out once the RPMs have picked and current has declined. A stalled motor draws a lot of current. As it picks up speed current drops off. Your frig motor probably uses a current relay.
    R!f@@ likes this.
  16. tinkerman


    Jul 22, 2012
    Typical motor connections
    R!f@@ likes this.
  17. debe

    Well-Known Member

    Sep 21, 2010
    If you are going to try a timer it will need to have some trim ajustment. As the motor will probably take a little longer to reach 75% speed under load in the pump, compared to on the bench. A relay probably wouldnt be acceptable in a Fuel pump aplication. Fridges that are using LPG as a refrigerant dont use mechanical start relays. They have to use a PTC to activate the start windings, so there is no spark. But they do need a cool down period before the next start.
    Last edited: Dec 14, 2012
  18. tinkerman


    Jul 22, 2012
    Yes electronic start relays are also used. In this application all the components need to be inside the motor. My intention was to give some motor basics.
    R!f@@ likes this.
  19. R!f@@

    Thread Starter AAC Fanatic!

    Apr 2, 2009
    I am learning a lot here.

    The diagram in post #18 shows what I thought would the connection would be in Gilbarco.

    I need some more advice based on the current findings.

    Below is for the Chinese motor,

    The winding has 4 wires coming out .
    The resistance measurements shows two separate windings.

    The blue and white wire connection gives me 5.26Ω.
    The Red and black one gives me 1.533Ω.

    This was rated at 220VAC. 1000W. 6.2 Amps. 1420 rpm.

    The RED and Black wires are of lower gauge, Thicker wire connection, while the Blue, White has thinner wires.
    From this assume, the running are Red & black.

    This one has a single running winding.

    This motor now works perfectly if I can time the start come and running current I got was around 2 to 3 amps.

    Mind u tht the Run winding has low resistance

    Now the Gilbarco one

    This motor has five wires.

    All wire connections has equal wire thickness so here no help.

    One winding has 1.34Ω with color coding of Yellow & blue.

    The other has three connections of white ..Red & black

    The Other 3 are White, Black & Red.
    Black being the common.

    White -- 2.628Ω--- black ---- 1.329Ω ---- Red
    ∫----------------3.97Ω -------------------∫

    I presumed Yl & Blue being the start winding, wired it to the fist Gilbarco in my very first attempt.
    Disconnected the black and used Wh & R as the running.
    Fixed the center switched checked it thoroughly by manually rotating the rotor. And it worked perfectly.

    I was pretty sure it was working and tested it thoroughly
    And with a running current of around 6 amps

    After a few days they blew or it blew the start winding which has thinner winding which by the way has the lower resistance.

    My question is why the Start winding ashed. Could it be the 300μf starting cap ?


    I am now going tear out the wires of the other Gilbarco and check the winding separately. This thing is testing my patience.

    I just bought some new bearings . Will update with photos if I can.
  20. R!f@@

    Thread Starter AAC Fanatic!

    Apr 2, 2009
    Hers is my attempt to run the Chinese one



    Which by the way was a success.

    Below is the name plate of Gibarco


    I took the winding connection apart, coded them with heat shrink sleeves as per the original color coding.

    * one change is Instead of white now I am using Green color.


    Here is a Higher resolution if you need to look close

    Now I am going to measure the resistance and will post the details in the next post.