I am an avid turntable freak. It seems all my favorite classic tables have the same Papst "Aussenlaufer" Motor. I have searched for definitive info on the working voltages of this motor to no avail. This is a post on electronic 3-phase power controllers.
My Vinyl experience started young, around the house growing up we always had a Thorens TD-124 mk1 with the Papst motor. At some point I wanted my own turntable, and after various low-end free tables found on the street, I learned online about the Fairchild 412, and became obsessed with it. After reading about the tube electronic motor controller 412-4, I knew I wanted to build a 3-phase supply for my 412 and the Thorens. After getting an Empire 208, plus digging out my fathers older Rek-o-Kut N-33H, to my surprise both also had the Papst "aussenlaufer", it became even more of an obsession. So now I have 4 tables with the same Papst motor.
In the past year or two I have read of people (on this forum) using a Siemens micromaster 420 to run an EMT table outside of it's country of origin, plus gaining 3-phase power and adjustable speed control.
Well, being a cheapskate I bought the first 3-phase motor controller I could find on *bay. Looking at the specs written on the back I assumed I could variac the power from 0-220v, but the controller I found seems fixed at 220v output. Not wanting to damage one of my motors I first tried the lightbulb trick, for 3-phase I wired up 3 lightbulb, each in series with a phase, and voltmeters hooked up everywhere to measure voltage. Well, the table spun up fine, but bulbs did not light and voltage shot straight up to 220, so I cut power immediately, afraid to damage anything.
Than I remembered something in Fairchild 412-4 schematic and looked it up, low and behold the voltage changes from 150v-450v!!, 150v at 16rpm to 450v at 78. It states:
Another interesting fact is that as the frequency of the current is increased the reactance of the motor rises and hence the voltage applied to it must be increased to put the same current through the motor. For this reason, the switch also changes the output voltage. When operating at 16 rpm the applied voltage is 150 whereas on 78 rpm it is 450. This is accomplished by selecting an appropriate tap on the output transformer secondary...
There is also a chart with impedance of the taps for different speeds, so the other voltages can be calculated.
Primary impedance: 4500 ohm
16 2/3: 600 ohm
33 1/3: 900 ohm
45 : 1125 ohm
78 : 4500 ohm - 1:1 tap
It is stated in the same article that even if you buy a 412 without electronic speed control, you can add the motor controller in the future, telling me the Papst motor in my Fairchild might not mind taking 220v, and maybe needs even higher voltages for 78rpm operation. (btw, anyone notice the last 412 sold on *bay appeared to NOT have the Papst motor, never saw that before, seemed to be a late model...)
So to get down to my main question,
Do you think possibly all the classic Papst "aussenlaufers" are equal?
They sure look the same....., maybe the only difference between the European and American models is the spindle size? I am fairly certain the motor in my Fairchild will take it, but I really don't want to hurt it. I am of course interested in running the Empire 208, Rek-o-Kut and Thorens with the same controller, or possibly other HV (120vac+) 3-phase motors.
Does anyone have more experience with 3-phase power controllers with the older Papst motors?
Any real world experience with the Siemens micromaster or other 3-phase controllers would be helpful.
ref: Fairchild 412-4 Article http://img196.imageshack.us/gal.php?g=fair412edscand.jpg