Thread: 2HP Induction Motor Capacitor replacement

Jaycar are unlikely to have them but you never know. EBay but watch quality/Australia compliance.
Some electrical outlets (Ideal for example have some sizes when I needed one for a pool pump) or Machinery Warehouse.
There should be other places.

I think you will find that the cap in inside the plastic housing, you may still be able to read the value, Jaycar carry a couple of run / start cap values, you may get one close the value. Specified as Polypropylene motor Run capacitors - 450Vac or 480Vac from memory.

Mike.

you might find a local motor rewinder who can fix it cheap and likely has the needed parts

I have tried Jaycar in the past for them.... they have nothing, look on ebay, you will find what you need
Rob.

The travails of limited knowledge continue....

I took the capacitor out of the housing and it is marked BMI 400-480uF 125VAC. It looks exactly the same as this one on ebay - apparently the same make and label other than the ebay one is 250V which sort of makes sense for plugging in to 240V mains? Price is a bit steep though.

amazon.com.au have a cheapy simply marked 400uF 250V for less. Any thoughts on whether it would be a suitable replacement, dropping the upper 480uF from the range but upping the voltage to 250V?

<edit> I think the BMI 250V version is rated at 8amp while the 125V version is 4amp which makes sense if Q=CV, double the voltage, double the charge and the current to deliver it. Perhaps I should be looking for a 200-240uF 250V replacement?

The voltage rating on a capacitor is the maximum voltage that it can operate at. It should be at or above the supply voltage. Keep the capacitance value as close as possible to the original. That is the only value that matters to the motor performance. Although quality capacitors perform better and last longer, the Amazon one should work fine. The 400uF rating is for 50Hz and the 480uF is for 60Hz

I eventually found the matching replacement cap on the H&F website but actually got one from a local motor rewinder at the same price. Beat waiting for shipping from China and saving a few $. The guy at the rewinder said it's probably 125V because it might be connected to a centre tap on the motor.

The dusty starts up quickly again. I think the centrifugal switch is OK as I can hear it click back in when I switch the machine off, although I can't really hear it disengage during start up. I don't have a clamp tester to check current draw, but if I did, which line would be the one to check? The incoming power cord or one of the wires connecting the capacitor?

To check the motors current consumption you will need to put a clamp meter on either the active or neutral wires from the power point, but not on both. To check the current of the starter winding the meter goes on one of the wires feeding the capacitor.

Hmm. Dusty seemed to run well this morning, I felt the cap a few times to make sure it wasn't running hot, all seemed fine. First time I turned it on after lunch, I could hear a rattling sound and thought maybe something got sucked into the impeller, just before the new cap blew. Nothing stuck in the blades so must have been the centrifugal switch I guess. Bummer.

I took the motor off the DC and found the motor fan (not the impeller) had been rubbing on the housing and partially melted away. (The impeller, by the way, also had a bit of play on the shaft as the key seems to have worn away a bit of the slot in the shaft over the years.) There also appears to be a separate black nylon sheath used to match the arbor to the white nylon fan on the motor shaft. It appears this bushing might actually continue all the way through the centrifugal switch? There are shreds of black around the shaft inboard and outboard of the metal parts of the switch. I think this bushing must have disintegrated and blocked the switch from disengaging. There are metal dags and obvious arcing around the contacts.

m1.jpg m2.jpg m3.jpg

This is probably now beyond my capacity to fix.I'll have to take the motor to a reconditioner to see if it is worthwhile fixing.

These days electric motors are so cheap and ready avalible. For $200 you will get a new motor. It will cost you $150 just for sombody to have a look at repairing it.

Kirbz's reply raises the question - if I scrap the existing motor is it worth recycling the existing motor? There must be a few kg of copper in the windings, do the recyclers take motors as is or would the copper be need to be stripped off somehow?

Originally Posted by Fuzzie

Kirbz's reply raises the question - if I scrap the existing motor is it worth recycling the existing motor? There must be a few kg of copper in the windings, do the recyclers take motors as is or would the copper be need to be stripped off somehow?

Mixed scrap is priced at the cheapest component which will be the iron and on most motors unwinding the copper is a right PITA.

If you are replacing the motor and you are up for it you could consider a used 3Phase motor and a $100 VFD? This will allow you to run the DC at the 60Hz and push 20% more air though the impeller..

Originally Posted by BobL

Mixed scrap is priced at the cheapest component which will be the iron

That statement is incorrect. Electric motors are a recognised item in the scrap metal stream and attract a premium over the scrap steel price. However, you have one motor and the amount you can look forward to receiving will be minimal. If you want to ensure it will be recycled and not end up in the general waste stream drop it off at a metal recyclers or a motor rewinders.