ABOUT THE U100 ROTOR

This is an old rotor design but there are still plenty of them around. There are a few things that you should know about them though before you decide power one up:

1. I RECOMMEND caution when powering these rotors with a solid 24 volt AC source.

• Yes I know that is what the manual says the voltage is and a few articles have also indicated this is the correct voltage to use - BUT THERE IS MORE TO THIS STORY!

2. The transformer in the production control box does have an open circuit voltage of around 24 VAC.

•  HOWEVER, it has a high source impedance. So what you say! Well that voltage drops down to around 15 VAC as soon as the rotor is drawn up into the motor frame (like a solenoid) and the rotor starts to turn. That is, you start to draw power from the transformer. This solenoid action appears to serve as  a simple rotor brake.

3. If you use a "stiff", or low impedance 24 VAC source to power the rotor:

• The motor current may be too high (3 amps or so) and the motor may eventually fail- as happened to me.

• At 15 volts or so the motor current is about 1.5 amps and the motor wire seems to be sized for this magnitude of current.

• I was concerned that I might have trouble getting the rotor to pull up into the motor frame under some conditions using 15 volts but I have not seen this yet. The U100 may use the high voltage to get the energy to pull the rotor into the frame and let the high impedance of the transformer throttle the voltage to the motor windings once it starts to turn or/and to satisfy safety issues regarding the amount of energy the transformer can deliver - not sure of the original intent here but at any rate a "stiff" 15 VAC source seems to work fine.

4. If you salvage the transformer out of the commercial control box you should have the best of both worlds but I wanted to save the original control box as a reference.

5. I found the schematic on the U100 a little vague. Yes there is a dot there! One side of the pulser contact is connected to the common (terminal 3) of the motor winding return (to the controller box).