Re: John Freau's phase adjuster- a few questions

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: FutureT-at-aol-dot-com 

In a message dated 11/17/03 7:09:59 PM Eastern Standard Time, 
tesla-at-pupman-dot-com writes:

>Hi all, (esp.John),
>
>I have been putting together a Freau phase adjuster for my big coil
>system, since I have a salient synch 3600 RPM Wysock rotary gap.
>The motor is 1/2 HP and I am using a 140 volt, 10 amp variac that I
>modified so that the variac is simply a series inductance with the mo-
>tor/capacitors inastead of the 120 VAC in, 0-140 VAC out setup. Any-
>who, I am using (2) 100 uFD, 370 VAC run caps plus a single 15 uFD,
>240 VAC run cap for 200 or 215 uFD. I put the voltmeter to the terms
>of the motor input and looked for the resonant rise in the range of the
>variac's knob. At first the voltage does decrease a bit after the variac's
>inductance is added to the circuit (about up to 20 on the 0-140 scale
>of the knob) but then does begin to increase slightly between about
>25 and 60 ( w/ 200 uFD - about 70 w/ 215 uFD) on the knob. I never really
>got a 3 to 5 volt increse in this range, more like a 1.5 to 2.5 volt increase
>(it was kind of hard to get an exact voltage change amount as my
>lines voltage constanly varies by a couple of volts). Anyway, is a 1.5
>to 2.5 volt increase good enough or does it need to be at least 3 volts?



David,

A certain voltage increase is not really needed.  It's just that a 5
volt rise often lets the motor stay in sync-lock to the end of the variac's
range.  If you're willing to tolerate a partial variac knob-range, then
it's probably OK.  The phase will still shift OK and to its full extent.
You can put some sort of "stop" on the variac so the knob can't be
turned too far.

>I can hear the motor changing phase a little by its sound, so I must
>assume that it's at least partially working.


Yes, it's most likely working to it's full and proper extent.

Even increasing the cap

>to 230 uFD (I have about (25) of those 15 uFD, 240 VAC caps) didn't
>seem to change the voltage from resonant rise by more than 2.5 volts
>or so, but the higher capacitance did seem to extend the phase adjust
>range on the variac knob as well as not allow the voltage to drop as low
>from the initial adding of variac inductance in the 0-20 range of the knob.


Yes, increasing the cap value normally has those effects.

>If I turned the variac knob up too high (past 110 on the knob) the motor
>would suddenly start slowing down and bringing the variac knob back
>toward lower inductance would cause the variac to make an awful hum-
>ming sound until the motor finally reached back up to it's full speed. Is
>this the "self braking" that John was referring to?)


It's not the self braking effect, but when what you're seeing happens,
it's best to shut down the circuit, then turn the knob to zero inductance
and then start up again and adjust the phase (avoid the awful humming).


>Also, I placed a 10 amp fuse between the capacitor(s) and the line hot
>from the line voltage supply to the motor and it worked fine when just
>running the voltage from the phase adjuter to the motor via an extention
>cord (100 ft), but blew the 10 amp fuse twice in a row when I ran the voltage
>via the grounded shielded nomex (18 ft) from the cap to the motor. I wonder
>if the "Blumline effect" is possibly causing this?


Did the fuse blow when the motor lost lock and you had to try to
get it back into lock with the awful humming sound?  It's best to
avoid the awful humming by not letting the motor ever lose sync-lock.

I finally placed some foil

>around the fuse since I didn't have any more 10 amp fuses handy. Funny
>thing, though, the 10 amp (or maybe 15 amp?) fuse in the variac itself
>nevre tried to blow, even after defeating the phase adjuster fuse w/ the foil.
>Any help/expertise would be greatly appreciated :^)


The part of the circuit that contains the protective fuse experiences
resonance, which increases the current in that area.  For this reason,
it's best not too use a too-large cap either.

John


>David Rieben
>