In this video, I will show you how to connect the single-phase induction motor in cap start configuration.

The supply goes directly to the main winding. From one side of the main winding, we go to the auxiliary winding. From the other side of the auxiliary winding, we go to the start capacitor. From the start capacitor, we go to the switch. This switch will replicate how the centrifugal switch or a start relay works, so we’ll have a manual control over it. And this is finishing the circuit.

Right now, the toggle switch is in this side. We haven’t written down on or off deliberately, but this side is on, and this side is off. So you can see that when you turn the power on, you can see nothing happens, so that means that’s off. Let’s turn the centrifugal switch on. Turn it on. We can see how the motor is turning. And if we turn the centrifugal switch off, motor continues to turn. Let’s measure the current in this circuit.

With the centrifugal switch on, I’m going to turn on the motor. You can see we’re drawing almost 530… Let’s say 530 milliamps. And when the centrifugal switch turns off, the current goes down to 178. So the start current is a lot higher in this. Let me try and stall this motor with the centrifugal switch off. You can see it’s quite easy to stop, stall and stop, and it’s drawing about 300 milliamps. But if I turn the centrifugal switch on, you can see the motor picks up. At this stage, if I was to try and stall it, it’s actually a lot harder to stall, and you can see how the capacitor is working against the force that I’m trying to put on it, and it keeps picking back up.

So a motor of this type would work in a way when the centrifugal switch is on when it’s off. When the motor is off, as soon as you turn it on, motor picks up. Once it’s reached enough speed, the centrifugal switch turns off, and it maintains the speed. If the motor was to slow down for any reason, the centrifugal switch comes back on and keeps the motor going, give you the higher torque that you need. And once it’s back on speed, it will turn the centrifugal switch off again.

Let’s measure the voltages while the cap start motor is running and then when the cap start… the centrifugal switch is on so we can see the voltage differences in both situations.

So, right now, with the capacitor off, we have 44 volts on the main winding, 26 volts, 26.5 volts on the auxiliary winding. So 9 volts across the capacitor. But as soon as we turn on the centrifugal switch, we can see there is 61 volts across the capacitor and almost 80 volts across the auxiliary winding, and the main winding is still at 43. So you can see what the capacitor is doing there.

You have to be careful. None of these capacitors have a bleed resistor, so you will have to discharge those capacitors manually or through the motor. So if I turn it off now, you can see how the capacitor is discharging, and it’s almost discharged now.

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