Electric motor question.

[Bill Douglas]

I bought a cheap 240 volt electric lawn mower from the recycling shop at the dump.

I like it, nice and light, and does a good job. But it dies after about two minutes. I release the lever on the power switch then pull it back on and it goes for thirty seconds, then same again etc.

I thought it may have an overheating sensor that is not working right. But there is not much to the thing. The power goes to negative and positive (phase) terminals on a little box 1" x 1" x 1/2" then two wires come from that into the motor. This part may be a rectifier - I don't know. I suspect it's the part causing trouble. Can I just buy any ole cheap 240 volt rectifier from an electrical store and solder it in?

Thanks. It's only a dump shop mower, but it would be nice if it went well.

[wswartzwel]

It may be a DC motor. Check the brushes to see if they are worn away and not making contact with the commutator. should be a small cover on top of the motor to access the brushes. Testing the DC voltage output from the Rectifier may also tell you if you are losing voltage after 15-30 seconds. Floor buffers use a similar system, I have seen them fail due to the winding in the armature breaking and losing connection. an armature for one of those motors is sometimes more expensive than it is worth.

[Bill Douglas]

The brushes looked OK, but thanks.

[wswartzwel]

Voltage check coming from the rectifier would be next.... You can also get ohms readings across commutator to see if there are any open windings... as well as resistance from each commutator to the armature shaft to see if there is a shorted winding. You should be able to find manufacturer tag and google a parts list online to locate the right rectifier... it will need to handle whatever amp rating the motor requires. sounds like a fun project.

[Bill Douglas]

Thanks. There are some numbers on the rectifier. If this is what the problem is. For some reason I'd like to haha win this battle with the dump mower.

[Zeke]

There is a reason it was at the dump.

Someone had to say it.

[Bill Douglas]

I totally agree. But the Scottish in me... I can't help myself.

[john70t]

Bypass the phase induction to the warp core.

[KFC911]

Once the dilithium crystals croak...dump time!

[Bill Douglas]

Thanks Guys for your help.

I googled images of electric motors and it turns out the electrical thingy is a capacitor.

In it's capacity as a dump shop mower I decided it didn't need one so I removed it and the mower works fine. I mowed the whole lawns without it missing a beat.

[nota]

it will have MORE POWER with a new cap

a cap is a trick to boost starting power by storing and burst release of energy

[wswartzwel]

Cool...