I like it.

At work today I opened waterpump wiring terminal boxes as I thought, why not test the amperage through each winding. I found the following:

Water pump 1

2.7A through the 20uF Capacitor
3.1A through Live wire

Water pump 2

1.86A through 20uF Capacitor
3.67A through Live wire

Water Pump 3

2.48A through 20uF Capacitor
3.44A through Live Wire


Assuming I've clamped my meter in the correct position which Im almost certain I have, and assuming the motor is basically the same wiring as this diagram than the current though the "Running Winding" would be about 0.4V. Calculated simply by subtracting the current through the cap from the main live wire current. This running winding I thought would actually be drawing more current but perhaps it is not due to having a much larger inductance value.
View attachment 354594


Further info:
- The water pump is rated to run at 4.6A maximum
- The MCB connected is a 10A

That looks interesting. It reminds me of a time when I was very young and my father brought home a really expensive grinder that had stopped working. I checked it out and found the reason it was not working was because it could not start turning. The cap was bad.
I did not have the means to get a new cap back then, so I used a push button. The push button energized one of the windings to get the motor started, then all you had to do is release the button and the motor would wind up to full speed.
Thus we had a pretty nice grinder for almost no cost.

I am not sure though if all motors can run that way. Once the motor starts, the button is released and so the start winding no longer gets any current at all. A cap start motor would normally have some current flowing even after it starts.

 

That looks interesting. It reminds me of a time when I was very young and my father brought home a really expensive grinder that had stopped working. I checked it out and found the reason it was not working was because it could not start turning. The cap was bad.
I did not have the means to get a new cap back then, so I used a push button. The push button energized one of the windings to get the motor started, then all you had to do is release the button and the motor would wind up to full speed.
Thus we had a pretty nice grinder for almost no cost.

I am not sure though if all motors can run that way. Once the motor starts, the button is released and so the start winding no longer gets any current at all. A cap start motor would normally have some current flowing even after it starts.

Nice. That motor may have been the type where the start winding is connected to a certifugal switch so your push buttton was acting as the centrifugal switch. However, if you remove the capacitor on secondary winding there will be no 90 phase shift on the field so it will not be rotating. So i am confused as how you got it to start. What produced the starting torque? Did you spin it by hand?

 

Nice. That motor may have been the type where the start winding is connected to a certifugal switch so your push buttton was acting as the centrifugal switch. However, if you remove the capacitor on secondary winding there will be no 90 phase shift on the field so it will not be rotating. So i am confused as how you got it to start. What produced the starting torque? Did you spin it by hand?

Oh yes maybe it was the special centrifugal switch that would open when the speed got up to a certain level thus opening the start winding. That would explain it better. This was many decades ago
No spin by hand, just the extra winding energized then disconnected later.
It had a pretty big motor for a bench grinder (used to sharpen chisels and drill bits and whatnot).
I used it a couple times to make specially shaped decorative stones from stones found in various areas in New Jersey. Also made a nice-looking stone guitar pick from a really beautiful stone (might still have it around).

 

Yeah, sounds like it was broken cause centrifugal switch was stuck open and when you replaced with push button it pretty much did same thing. Clever

It is very satisfying when your bring electronics back to life