5HP motor capacitor replacement for older motor I cant find info for anywhere

Thread Starter

unclemikey

Joined Feb 11, 2015
10
Hello,
I have this used motor ,I cant find any info on this company or model number and cant find good advice on how to calculate what start and run caps I should get. I can see motors like it ,but do not know the corrcect name for what type of ac motor it would be considered.I have a feeling the caps currently here were put in from what may have been on hand.The start caps are rated at250VAC and my line is giving 243 volts,so I want to replace them with higher rated Voltage ones,but want to get the "right" ones,the start cap without the resistor has a drop of oil that started to leak. I can add this motor will be used to run a hydraulic vane pump coupled by a lovejoy style flexible coupling.The motor will run,but I feel heat after few seconds near bottom if I place my hands on motor above foot flange on both sides.I have changed both bearings and feel they are running smooth.I clamp metered amps for wires while running and added those to my wiring diagram.I read on internet that the correct running cap will reduce heat and make the motor last longer than the wrong mfd rated one.If anyone could lend some knowledge I would greatly appreciate it.
Thanks Mike20211026_135110.jpg20211025_232354.jpg20211026_123926.jpg
 

MaxHeadRoom

Joined Jul 18, 2013
23,898
For a 5HP motor I would expect a high value electrolytic for start and the lower value one for run.
The start capacitors should be motor start rated, likewise the run capacitor should be Motor Run rated.
If there is a centrifugal switch, the larger value electrolytic would be in series with the switch, the run cap is connected permanently, the run winding is the lowest resistance winding and has no capacitors in series with it.
Have you distinguished each winding with a resistance test?
I would expect a minimum 200ufd for start cap and a 15uf to 20uf for run
 

Thread Starter

unclemikey

Joined Feb 11, 2015
10
would I add run capacitance value to get to a 90 degree shift,could that be figured out ,would that be ideal for the motor to run best?
 

MaxHeadRoom

Joined Jul 18, 2013
23,898
The lowest (1.5Ω) would be the run winding.
The ideal is as close to 90° as possible.
You would need the inductive reactance of the winding at the applied frequency! ;)
 

Thread Starter

unclemikey

Joined Feb 11, 2015
10
Thank you Max.Does anyone have any info on Leyland-Faraday XM-005B,or what type of motor is thier type XD,from the name plate? There are 2 starting capacitors used in series in this motor,would that reduce the MFD of the pair? Why do they use a series pair? Info I gather and told to me byMaxHeadRoom ,a mfd of 200 would be recommended,would I get 2 single 400 mfd caps, and in series they would give me the 200 mfd?Why are there 2 start caps,I cant find any information anywhere ,when I search 2 caps ,2 start caps,etc.,I get "one is a run and 1 is a start".This motor does have a centrifugal switch, I tried to draw what I see in the center image ,that cuts the start capacitor pair after start.I got hold of an LCR meter today and seems the run cap is giving a rating same as its name and the start caps are toast,I thought that may be since they were only 250vac rated,which adds to me not trusting what was in there when it came "used" to me.
 

MaxHeadRoom

Joined Jul 18, 2013
23,898
The only reason I can see for two start caps in series is to half the value but double the voltage rating?
They should be motor start rated and generally constructed of solid electrolyte, no polarity markings.
In fact All caps used in motor start circuits should be motor start rated for that purpose..
 

Thread Starter

unclemikey

Joined Feb 11, 2015
10
The 2 start caps are only rated for 250 VAC each,which seemed too low to me,but if the voltage gets split,it makes sense.There is a leak from one and I want to replace them,being there are 2 with matching covers that look as if they came that way, could it be that the maker had many lesser rated VAC caps to "use up" ? Could I replace the 2 ,with 1 of similar MFD of the pair, and higher voltage ?
 

Thread Starter

unclemikey

Joined Feb 11, 2015
10
I think a single is what Ill try,the old set was two 216-259mfd,and in series would be 216-259 x .5 =109-130mfd. i see voltage share of 2 ,250 vac caps,but if either goes,the other has no chance. A single cap has less points of failure. I read somewhere that testing done with,a bad cap ,a weak cap, and new cap,first two had high amp draw at no load even after centrifugal switch cut out and that may be the heat I feel in this motor.I can order one for less anyhow.
Thanks for your help Max
 

Thread Starter

unclemikey

Joined Feb 11, 2015
10
After measuring the capacitance of the start pair and all three of my capacitors,I came to the conclusion that the start caps are wired in parallel,one is leaking but will give a reading if it is not on its side, and the capacitances add ,so I guess I couldn't see what was what from what.Looking at the magic marker drawing I posted I can now see that the pink spaghetti line is connected in parallel,otherwise it would not come back to the center caps other lug ,it would bypass that and land on the run cap I think, oh well,Im learning,more like remembering.
 

Thread Starter

unclemikey

Joined Feb 11, 2015
10
Max,
I ordered a new pair of start capacitors and want to replace them in the same wiring that was there(parallel) and the new ones do not have a bleeder resistor,would adding a resistor on one of these paralleled capacitors be ok to discharge both of them ,or should I add a resistor across each one? The old ones had 1 resistor across one of the 2 start caps,I wanted to ask advice because the cap that leaked and failed is the one that didnt have a resistor across it.
Thank you ,
Mike
 

MaxHeadRoom

Joined Jul 18, 2013
23,898
I do not really see any reason for adding a bleed resistor on start capacitors? It is not common practice.
What value are the resistors? If it was to make it easier on the start switch, I cannot see it acting fast enough, if wishing to add one, place one resistor across both.
it is unusual to see leakage on a motor start electrolytic as they are typically solid electrolyte?
 

Thread Starter

unclemikey

Joined Feb 11, 2015
10
In shopping for start capacitors I noticed many coming with a resistor , the old pair has a resistor on one of the two.I am not certain why they use them.I have a lot of resistors around and thought if it helps it would be easy to add any value one in there.
 
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