Re: [TCML] SRSG with John Freau Phase Control

[Quarkster <quarkster@xxxxxxx>]

Mark -
 
Glad to hear that your phase controller is working well.
 
However, I did have a question about your synch motor. Regarding the motor windings, you mentioned the ratio of 3 resistances "between the three wires....".  In your Wikipedia link to the semi-star winding diagram, it appears that there are only two windings that you can access through the motor leads (W1 to U1, and W1 to V1). Please clarify how you measured the three different resistance values.
 
Quarkster

--- On Thu, 8/2/12, SusaX2 X2 <susax2@xxxxxxxxx> wrote:


From: SusaX2 X2 <susax2@xxxxxxxxx>
Subject: [TCML] SRSG with John Freau Phase Control
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Date: Thursday, August 2, 2012, 3:09 PM


Hi Guys,

today I finished my new SRSG with John Freau's Phase Controller.
Here's a youtube video of the assembly in action
> http://www.youtube.com/watch?v=83ZdeQyoCqQ <

Since I don't have a scope I found an easy way to check if
the motor runs in sync and also the adjustable phase angle.

I took a strobe light used for checking ignition timing and
connected a small and simple mechanical relay (from tv or microwave PCB)
to where the signal clamp used to be.
The relay is connected via single rectifier diode to a small transformer
powered from mains.
This way the strobe flashes 50 times a second, mains frequency ofcourse.
(The tricky part was getting the camera's shutter time right..)

The motor is a 2HP 3000rpm 50Hz 220V single phase induction motor
with 2 flats milled on the rotor for salient pole operation.
The motor has it's original 30uF run capacitor and
it is internally wired semi star, since resistance between the 3 wires has
a 3:2:1 ratio
> http://nl.wikipedia.org/wiki/Bestand:Steinmetzschema-3.svg <

The phase controller has a 5A variac and a 18uF run capacitor
with a 1.5MOhm bleeder resistor. (And a 10A fuse ofcourse
to protect the variac in case the brown stuff hits the fan)

It has almost 90 degrees phase control over 70% of the variac's range
before loosing sync. I didn't measure any voltage rise at all,
voltage starts dropping as soon as the variac is turned.

I reckon almost 90 degrees is a maximum for a 3000rpm motor
and almost 45 degrees max. for a 1800 rpm motor.
This should make sense if you consider the 2 (or 4) field windings
and the position of the milled flats;
If you push the rotor to the point where the 2 flats meet up
with the point where the 2 field windings separate,
it's fighting 2 opposite magnetic fields.

Many kudos to John for inventing the phase controller.
I will though, accept all credits for the method
to check if the thing's working or not ;)

Mark
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