is the capacitor superfluous?

[Brigadier]

Hello,

My garden shredder started smoking a couple of days ago.

I've taken it apart, and found that the capacitor has melted completely through (which I presume is the source of the smoke).

However, the thing keeps on going!

My question - can I just chop the capacitor out, and re-wire to the motor, seeing as it doesn't seem to have affected the working of the shredder?

What does the capacitor do anyway?

(It's a B and Q 1800 shredder, with a "single phase capacitor running motor". It's well out of warranty).

 

[Spark123]

Think it is there to cause a phase shift creating a rotating magnetic field which causes the rotor to spin.
If you cut it out the motor may not spin or not start without you giving it a turn.
That is unless it is one across the supply provided for PF correction (do they do this???)

 

[bernardgreen]

It is essential

The motor has two coils and requires that the AC supplies to them are out of phase with each other.

The capacitor creates an AC voltage out of phase with the supply to provide the voltage for the second coil.

It may still run but will almost certainly be less powerful and may run in reverse. If it is overloaded and stalled when working it may reverse direction and throw stuff backwards out of the machine.

single phase capacitor running motor

and not a capacitor start motor.

 

[Brigadier]

Ok,

purchased what I believe to be a suitable replacement for the melted one.

Trouble is, Maplin don't know which terminal is which, and the manufacturer isn't answering my emails

I'm presuming (with the help of my trusty multi-tester) that the two pins on the same side of the raised line are of the same polarity, and the two pins on the other side of the line are of the opposite polarity (first photo).




Also, I interpret the double arrow symbol on the bottom-right of (second photo) to mean that the capacitor is not polarised, and therefore I can wire it up either way.

Are the above presumptions true? Is the capacitor ok for the shredder?

Untitled

• Brigadier
• 1 Mar 2009
• 1

Untitled

• Brigadier
• 1 Mar 2009
• 1

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[Spark123]

It should be easy enough to tell which pair are common to each other using a multimeter - it seems logical that the line separates either side of the capacitor. You just need to use one from either side, I doubt it will be polarised as AC changes direction 50 times a second.

 

[sm1thson]

^agreed (although to be pedantic it changes direction 100 times a second, and completes a full cycle (2 directions) 50 times a second)

 

[OilLecky]

This capacitor is not polarised. Determine which terminals are common with your multi-meter and connect one cable to one side and one to the other.

(There are some capacitors that are "polarised" and they are known as "Electrolytic capacitors". They are marked as Positive and Negative or have a red mark on the positive conenction. )