I am just an amateur and I have a go at repairing anything and never throw anyting away. I have a small Mn80a lathe that I bought in 1996, with a 0.55KW / 0.74HP 3 Pase Motor.
I purchased a MOTORUN Static Phase Converter to run it which has worked perfectly until recently, I tried to contact the firm without succesess. The problem is that the Motor would not start and the Contactor was switching on and off quite fast banging the side of metal case.
I think the fault is with one or more of the 30 Year old Capacitors, There are five, two are for Starting in High or Low mode. In Low Mode only one the 20µF C5 is in circuit. in High Start Mode an additional 31.5µF Capacitor c4 is switched in parallel to C5.
There are 3 Run Capacitors I have labelled C1 10µF, C2 6µF and C3 6µF. there are two HP output settings LOW (1/8HP – 1/2HP) and HIGH (1HP – 2HP). in LOW setting C2 and another are in parallel in the HIGH setting all three capacitors are in parallel. Unfortunately I made an error tracing out the circuit. and now I am not totally certain which pair of two capacitors are in circuit for the Lower HP it is either C1 & C2 OR C3 & C2. of course it does not matter for the High HP setting as all three are connected in circuit in parallel.
I have purchased a new set of all Five Replacement Capacitors.
Does anyone have one of these, and if so I would be very grateful for some help to resolve my problem. I have attrached pictures, although I am not sure what all the Transformer secondary windings are for, but as I have not moved any of them I don’t think there will be a problem there.
Sorry, I don’t know any thing about your motor run device, you appear to be knowledable on matters electrical, but before removing the exist capacitor do ensure they are fully discharged. This can be done by short circuiting each capacitor terminals with an old screw driver, I hope I’m not telling grandma how to suck eggs. As you have already bought the new capacitors and haven’t disturbed any of the wiring why not fit them and see if the converter then works as before. I think the transformer is wired as an auto transformer, non isolating. Converters are now a thing of the past, inverters have taken over, so might be worth while altering the motor connections to Delta and fitting an inverter.
Ages ago I had a similar MotoRun static converter and should still have a circuit digram somewhere. I found the instructions for another correspondent a while back but unfortunately the circuit had gotten separated. I’ll have another look.
Failing that I should be able to figure out the correct connections for you. I’ve built static and rotary converters in the past so I was familiar with whats going on. Digging back 30 odd years for the right memory isn’t a Sunday evening job tho’. Need to be bright eyed and bushy tailed!
Thank you ever so much replying to my call for help. I used to buy MEW magazines, but the shop in Lancaster only ordered a few and I sometimes missed out, I have heaps of them and also some Hardback bound, I might start getting them again, I love looking through them, that is how I got the idea of joining the Forum.
I have a slight very small confession, I did not make details of the Transformer Secondary wires correctly as I was not going to have anything to do with them and after looking at my circuit I realised I had not drawn the Transformer connections accurately so I have put this right just in case it was of any help to you. This is how the wires really are. The empty Connector block at the bottom is only used as a 240 Volt Live supply to connect it to the Contactor. (RLC 21-22 on my diagram.)
I have already removed the Capacitors still connected together, thank you for reminding me about that Hazard though, I had actually removed them without checking, oops. but I think the Capacitors are discharged automatically anyway through the 1M Resistor R3 across C2. C2 is always connected in circuit. But I shall definitely make a discharging probe for when I get around to rebuilding the circuit.
I have searched the Internet for information about this unit, and I have not found anything at all apart from one thread on this Forum but that one has a 3 position Hourse Power Switch and also has a more complicated circuit with a highly populated Circuit Board, this is the thread I found. -:
I would love to see a proper Circuit Diagram if you find it, I kept everything I recieved from MOTORUN even the reciept.BLIMY ££ but the info supplied is not all that helpful, just instaltion and how to use it, the firm seems to have vanished.