Hey guys.
I have a really good bench grinder an old one that is robust and well built as they are back in the old days haha.
The capacitor has let go. Now the grinder has no centrifugal switch so I’m assuming it needs a motor "run" capacitor NOT a start up capacitor as it has no centrifugal switch so I guess the capacitor is in circuit all the time. I found this cap in my draws and my question is: is this the type I need? And how do I know?
The photo is the one on the left is the old one and the right is the new one I have.
I just want to make sure as 240v can be lethal plus an exploding cap is definitely not what you need!!!
Cheers
I have a really good bench grinder an old one that is robust and well built as they are back in the old days haha.
The capacitor has let go. Now the grinder has no centrifugal switch so I’m assuming it needs a motor "run" capacitor NOT a start up capacitor as it has no centrifugal switch so I guess the capacitor is in circuit all the time. I found this cap in my draws and my question is: is this the type I need? And how do I know?
The photo is the one on the left is the old one and the right is the new one I have.
I just want to make sure as 240v can be lethal plus an exploding cap is definitely not what you need!!!
Cheers
The extra 1uF doesn't matter and the voltage looks OK.
I would mount the replacement on a cooling surface as they may run warm.
I would mount the replacement on a cooling surface as they may run warm.
thankyou so much 🙂 sweet yeh I think the extra uf will change torque slightly but that shouldn't matter much. So it's suitable for a motor without a centrifugal switch? so it can be in circuit all the time with 240v on it continuously?
The grinder has a PSC motor. It must have the capacitor in circuit for proper operation otherwise it overheats, runs too slow and eventually trips thermal overload or burns out.
New capacitor will help it spin up quicker.
New capacitor will help it spin up quicker.
The new capacitor is almost certainly a metal film capacitor. It will work but is not really designed to handle current. This will cause it to fail quickly. You should get a higher current foil and film motor run capacitor intended for higher horsepower motors. The type you show is often used with very small motors and still fails in use.
400 VDC is only about 125 VAC. (Note both capacitors shown have AC ratings. The newer one is rated for voltage only, not power! The old one should be able to handle more than 1.5 amps.)
Been there done that.
Just for grins, after it fails you can take it apart and unwind it. There will be a nice line the length of the film where the metal layer has burned off. That does not usually happen with metal foil units.
400 VDC is only about 125 VAC. (Note both capacitors shown have AC ratings. The newer one is rated for voltage only, not power! The old one should be able to handle more than 1.5 amps.)
Been there done that.
Just for grins, after it fails you can take it apart and unwind it. There will be a nice line the length of the film where the metal layer has burned off. That does not usually happen with metal foil units.
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I AGREE! Get a motor run capacitor.. Should not be too expensive. <$5.00 us
A 5mfd capacitor will have about .5 to .7 amps across it.
A 5mfd capacitor will have about .5 to .7 amps across it.
Without a motor-run cap or some alternative inductive phase-split, the motor won't start (and will burn trying).
With a motor-start cap in a permanent-split, the start cap burns up later today.
A cheap run cap will burn up next spring (in air-conditioner work).
Mackay Australia is a not-so-small town on the Coral Sea, hot and probably fishy? Unlike my smaller cooler town, it has plenty of cooling technicians and supplies shop. They can supply a known-good 5uFd line-voltage run cap.
With a motor-start cap in a permanent-split, the start cap burns up later today.
A cheap run cap will burn up next spring (in air-conditioner work).
Mackay Australia is a not-so-small town on the Coral Sea, hot and probably fishy? Unlike my smaller cooler town, it has plenty of cooling technicians and supplies shop. They can supply a known-good 5uFd line-voltage run cap.
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Hello,
Like PRR said the shops shown in his search will be able to sell the kind of cap you need. No need to use mouser this time. Greetings, eduard
Like PRR said the shops shown in his search will be able to sell the kind of cap you need. No need to use mouser this time. Greetings, eduard
Thanks guys so much!!
I managed to get down to the local shop and they had a 5uf 400v cap but they kept saying it wouldn’t suite because it’s 400v and I’m like huh???
I managed to get down to the local shop and they had a 5uf 400v cap but they kept saying it wouldn’t suite because it’s 400v and I’m like huh???
Voltage is not important as long as it equal or greater if it fits .
I hope not to have to buy in Australia as I get them less than $2.00 us. (HVAC tech)
I hope not to have to buy in Australia as I get them less than $2.00 us. (HVAC tech)
Thankyou I thought the voltage can be higher. So you reckon I should try it? Is there anything to confirm that it is a run capacitor and not a start-up one? I don’t want it to blow up as the motor does NOT have a centrifugal switch to keep the cap out of circuit after it starts up.
Cheers 🙂
Cheers 🙂
That "B" and "C" are only test conditions under which the voltage is rated. So just go ahead.
I am experiencing deterioration in the value of the capacitor.
This time I replaced it with a metalized Polyprolene film capacitor. Hoping it to last longer.