Electrical advice please

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Philip & Sandra Box
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I have a little 185W single phase motor that does a very nice job of running the tumbler through a little 15:1 gear box. The only problem is that it needs a nudge to start.

Motor wiring.jpg

I decided that it needed a capacitor to get it cranked up so last night after the 41°C had backed off a bit I went out and wired in a capacitor. Now it starts instantly and I thought all was fixed but that's not the case. It doesn't have a start capacitor disconnect so it very quickly runs too hot.

Any suggestions?
 
Flash Jack said:
Start capacitor?
Click to expand...

Yes without the capacitor the motor sits stalled until it is cranked either CW or CCW and from there it runs smooth and quietly. As soon as I touch the bowl even when it's fully loaded the motor fires up but from standstill there's no action. The capacitor changes all that so that now as soon as the switch is flicked the motor starts.
 
According to the picture the motor already has a 14 microfarad capacitor and I assume internal to the motor. If it is not turning when switched on, it is likely that the static load is too high. Adding a capacitor can be problematic if not the correct size, including explosion. 185W is roughly 1/4 HP. As a guide, most washing machines range from 180W to 360W or 1/4 to 1/2HP, depending on washer size, some up to 800W, around 1HP. Your answer might be a bigger motor. If memory serves, the switch symbol on the white wire is a centrifugal switch which opens when the motor has started. The only replacements, should be the 14mF capacitor or the switch as they do wear.

The centrifugal switch is generally made from thin phosphor bronze strips with a contact at the end. As the motor increases speed, weights act on a ring cam to open the contact, so this mechanism also needs to be checked.

The idea being that once started the capacitor is not powered as the switch opens, adding one that is constantly powered is the danger.
 
Capacitor also a lot of times the cause for Gen sets no longer charging. Have had two this week with same issue. Easy to check as usually you will see swelling of case or even a hole blown out the side. Best part is they are cheap as chips just make sure you use one as same capacitance as that removed. Also two types, a start capacitor and a start/run capacitor. You can use a start / run capacitor in either application but not vice versa.
 
Last edited:
Moneybox said:
I have a little 185W single phase motor that does a very nice job of running the tumbler through a little 15:1 gear box. The only problem is that it needs a nudge to start.

View attachment 6264

I decided that it needed a capacitor to get it cranked up so last night after the 41°C had backed off a bit I went out and wired in a capacitor. Now it starts instantly and I thought all was fixed but that's not the case. It doesn't have a start capacitor disconnect so it very quickly runs too hot.

Any suggestions?
Click to expand...
I am a technician not an electrician but in my view, if wired like that circuit diagram above, when the motor is not running, the capacitor would charge and give the motor a high current 'bump' to get going.
Once the motor is running, there is little voltage 'charging' the cap, all power is going to the motor.
When the motor stops, more power to the cap, ready for next start?
If things are getting hot, where did you wire in your cap??
 
so it very quickly runs too hot.
Either to large or to small capacitor will cause motor windings to over heat.
 
Simmo said:
I am a technician not an electrician but in my view, if wired like that circuit diagram above, when the motor is not running, the capacitor would charge and give the motor a high current 'bump' to get going.
Once the motor is running, there is little voltage 'charging' the cap, all power is going to the motor.
When the motor stops, more power to the cap, ready for next start?
If things are getting hot, where did you wire in your cap??
Click to expand...
Between the red and blue. The red is connective to active. The white neutral.
 
condor22 said:
According to the picture the motor already has a 14 microfarad capacitor and I assume internal to the motor. If it is not turning when switched on, it is likely that the static load is too high. Adding a capacitor can be problematic if not the correct size, including explosion. 185W is roughly 1/4 HP. As a guide, most washing machines range from 180W to 360W or 1/4 to 1/2HP, depending on washer size, some up to 800W, around 1HP. Your answer might be a bigger motor. If memory serves, the switch symbol on the white wire is a centrifugal switch which opens when the motor has started. The only replacements, should be the 14mF capacitor or the switch as they do wear.

The centrifugal switch is generally made from thin phosphor bronze strips with a contact at the end. As the motor increases speed, weights act on a ring cam to open the contact, so this mechanism also needs to be checked.

The idea being that once started the capacitor is not powered as the switch opens, adding one that is constantly powered is the danger.
Click to expand...

Ok, I didn't see that switch on the white wire. In that case one end of the start capacitor should go to the white wire? Then the capacitor will remain out of the circuit until the next start.

No it's not a load problem. The motor won't start when unloaded but it only needs a flick of the fingers to start it spinning.
 
Diginit said:
so it very quickly runs too hot.
Either to large or to small capacitor will cause motor windings to over heat.
Click to expand...

I think the reason it's running hot is because the capacitor should only be in the circuit on start. That switch in the white wire is the answer. I didn't think it had one but it must be there.
 
Some motors have a start capacitor only, others have a start and a run capacitor. In both cases there is usually a centrifugal switch for the start capacitor, which is depicted in the original post. The 2 usual fails are either the capacitor or the switch or occasionally both. The capacitor sizing is relative to the design of the windings, power and voltage etc. It should be replaced with the same size in mF and voltage. Under or over will cause the capacitor to overheat or not do its job. If the switch is stuck closed the capacitor is energised continuously and may "burn out" if stuck open, the capacitor is not doing its motor start job.

Hand starting will work, but don't leave it too long after power up or the windings will overheat as the energy applied is not being absorbed.
 
That has all been said already ? See above 🤣 🤣 🤣 Very supercilious 🤔
 
Last edited:
I think I have it all fixed. I have my neutral and active wires connected to red and blue (before I had the neutral on white) and I have the start capacitor connected between the neutral and the white. It starts and runs as expected although after 15 minutes it's quite hot but that might have something to do with our 40°C ambient temperature.

Solder1.jpg

Everything (and perhaps everybody) up here in this harsh climate goes hard and brittle after a while. Today my soldering iron went POP while I was using it. The cable was so stiff it snapped and shorted out.

Solder2.jpg

And then to delay things further I had to contend with these silly tamper proof screws. Anyway it's all fixed now with a rubber cable that will most likely last a lot longer.
 
condor22 said:
Well done Phil, yes things go brittle, nothing lasts forever, lol. FYI I bought a driver set that has just about every bit to fit security screws from Bunnings,
Click to expand...

I doubt Cue Bunno's will stock these. Then again with Cue Bunno's you just never know your luck. Stock moves so fast they don't even bother with a website 😅

Hopefully your on top of the problem Phil.
 
Ok, I can confirm this doesn't work. The wiring diagram indicates a switch on the white wire but I'm sure it's not there. The start wiring doesn't disconnect to the motor overheats. I tried to run it with a fan to keep it cool but the motor went up in smoke in the end. It was a nice quiet little thing too but I slipped back to CueBunno and got a bigger one. It has no wiring diagram or plate of any type so I don't know the wattage but it must be near twice the 185W motor it's replacing.

Just to prove a point I connected this motor up the same without the capacitor and ran it for about eight hours fully loaded. It ran cool and quiet but still had to be assisted to start. Then I connected the capacitor in the same way as the previous motor and it starts instantly when switched on. However it also runs hot very quickly because there is no centrifugal switch to disconnect the capacitor once started. These motors must have a remote switch somewhere in the circuit.
 
Simmo said:
Phil check out this LINK
Click to expand...

Yes Simmo that's what would work if these motors had a centrifugal switch. They are out of washing machines and I don't think the switch is in these motors at all. The best way to find out will be to pull the smoked one apart. It's already lying there with the cable snipped off so I'll open it up. The switch works a bit like a centrifugal clutch on a chainsaw, the weights just throw out and break the circuit. You hear them come back as a motor slows to stop there's usually a distinct click. That's not there on these motors.
 
This bloke has exactly the same circuitry in his motors. I need to get back to the multimeter and check it out.


 

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