Start up requirements of repulsion induction motor?

Re: Start up requirements of repulsion induction motor?

My grandfathers domestic water pump had such a motor, but it was 1/4 HP, and it sticks in my mind, 4 amps @ 110 volts. AC of course. It had a wound rotor, that looks somewhat similar to a DC motor, complete with brushes, but instead of being connected to a power source, the brushes were actually shorted to each other. Depending on motor design, the brushes may, or may not retract once the motor is up and running. The one on my grandfather's pump did not retract it's brushes, but I understand that there was a centrifugal switch that cut power to them once the motor was up to speed, but I could be wrong on that. Standard induction motors can benefit from a capacitor to help them get started, but the repulsion induction type is a whole different kettle of fish and usually had rather high starting torque anyway if I remember right. Another I saw in action several times, also on a water pump, would start at roughly half speed, and after about 10 seconds, the brushes would somehow reposition their angle and the motor would come up to full speed. But all this was several decades ago, and repulsion induction motors have long been relegated to history. They were old when I saw them, so if you have one of these motors, you have history in your hands.

Re: Start up requirements of repulsion induction motor?

Wayne, get out the grease gun when he isn't looking... at least you can keep it from seizing up.

think he would notice if you sprayed it with LPS3? would stop the rust.

Re: Start up requirements of repulsion induction motor?

Oh yes, I remember them well, too well.
I even applied a few years back.
They were used and even required sometimes by the electric Co. in the early days of REMC.
They could start, drawing no more than their full load current.
When they stopped making them 50 years ago, motor rebuild shops would pick them up, rebuild and resell.
Demand for them continued for years after motor companies stopped making them.

They started as a repulsion motor with brushes on the communtator.
On the bigger motors you could adjust the angle of the brushes which controlled how much current it would draw
and how much torque it would have on start up.
Then as the motor approached full speed it would lift the brushes and short all quadrants of the the communtator together with a cone.
This enabled it to run as an induction motor.

Probably the biggest issue with them was reliability.
The shorting cone , after a while, would not make contact on all sections of the communtator.
And of course they were expensive to manufacture.
We would not apply them now with the electronic options we have today.

Re: Start up requirements of repulsion induction motor?

Photowhit,

That 1800 w inverter isn't going to like a 1 1/2 Hp motor.
You need to put the motor back on Craigs list and get a 2 or 3 Hp three phase motor.
Run it with a VFD type phase inverter.
You can start the motor beginning at 0 amps with the amps ramping up as RPM rises.
Even at full speed and full load the amps will usually be less since the 3 phase motors are significantly higher efficiency
and run near unity power factor.
You can also vary the speed of the motor and even over speed it if you want.

One problem however, the inverter is probably 120 Vac and most any 3p motor will want 220.
VFDs want the same single phase voltage in as they deliver to the motor.
This means a transformer, or a different inverter.
You probably could get by with a 500 VA transformer using it in boost mode.
The transformer needs only be half the power rating when used in a boost configuration.