run motor capacitor

[Piero]

Hi guys

Trying to find a run capacitor for one of my air compressor.
Its a 1.5 hp motor and uses a 30 uf 450v run capacitor.

Had a quick look on flea bay. But they look physically smaller.
Mine is 90 cm long and 50 cm wide.

Any one know were I might get one????
Also I don't know to much about capacitors? ??
If the value is right. Are they all the same????

 

[brightspark]

Hi guys

Trying to find a run capacitor for one of my air compressor.
Its a 1.5 hp motor and uses a 30 uf 450v run capacitor.

Had a quick look on flea bay. But they look physically smaller.
Mine is 90 cm long and 50 cm wide.

Any one know were I might get one????
Also I don't know to much about capacitors? ??
If the value is right. Are they all the same????

as long as the values the same physical size doesnt matter as long as it fits in or on

 

[Piero]

Does the wiring matter
Was told that as long as one wire goes in and an other comes out. Which way round didn't matter.

I took a few photos on my phone first to prevent any mistakes. But some capacitors have spade ends and no colour coded wires

 

[pedrobedro]

I put a much physically smaller one on my pressure washer and held it in with gaffer tape and it works fine. I don't know about the polarity thing and if it does matter I must have fluked it. Checked up and they are not polarised.

 

[piman]

Hello Piero,

the best place is a motor rewind workshop, and to confirm they are not polarity conscious.

Alec

 

[brewdexta]

I swapped my compressor capacitor the other day, they can be wired either way, no polarity hence why many come with two black wires.

Cheers
Andy

 

[mr_splatter]

They are on an AC circuit in this application so they are not polarised. Smoothing caps and the like are polarised as they are used on the DC side of stuff.

 

[brewdexta]

On AC circuits NP type (non-polarised) are used, on DC its usually indicated which is the positive leg.

 

[the repair man]

Hi, as mentioned some capacitors are polarised, generally electrolytics, they will have a band up one side in black or with dashes on it to denote negative side.
The voltage doesnt have to be the same, only the capacitance, although a higher not lower voltage obviously. Size will matter, purely for surface area cooling, a smaller cap will probably overheat and die at some point.
Running caps tend to have set values, ie 30uf 415v, start caps tend to have a range, ie 370-450v
Its should be easy enough to find one, if your stuck, message me, I have plenty of caps, contactors, motors etc

Sorry brewdexter, completely missed your post!

 

[brewdexta]

Sorry brewdexter, completely missed your post!

NP Costa, you sound like you know your tantalum beads from your ceramics better than I do

Cheers
Andy

 

[500e]

370-450v AC

 

[Exuptoy]

Only really used on 1 phase ac motors to mimic the out of phase situation that a 3 phase motor would get purely with the 120 degree phase angle to start.

If you spin a 1 phase motor by hand to start it, even with a failed cap it should run.

 

[Piero]

Thanks for all yr help guys
Ended up buying one.

Even with the old one well and truly melted and ozzing out. The electric motor ran sweet
Runs fine with the new one as well.

What might cause it to melt like that???

 

[shenion]

Caps develop shorts that cause a lot of heat that boils the dielectric. The short may burn out and the cap still works but with less capacity.

I have seen caps where all is left is an empty can and a bunch of confetti.

 

[Exuptoy]

What might cause it to melt like that???

Age, fair use?