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Re: John Freau's Phase Controller

Original poster: westland <westland@xxxxxx>

Thank you for the added information John. I haven't adjusted the start/run cap value at all, but have kept it at 3microF (the cap that came with the motor). I'll try adjusting this to see what effect it has. Yes, the mini-gap motor you show looks to be the same as mine; I am running at 50Hz (1500rpm), and I stepdown voltage from 220vac to 120 vac with a transformer ... I've tried putting your circuit on both sides of the stepdown transformer, but don't see a difference in response. I am getting the 3-5 volt resonant rise with the 3microF value ... so this should be the 'sweet spot'. You haven't mentioned anything about the variac inductance ... is this critical, or simply something that you can adjust the cap around. John, when you implement the circuit, what sort of inductance range are you typically using?


Tesla list wrote:
Original poster: FutureT@xxxxxxx
In a message dated 1/21/07 1:06:08 AM Eastern Standard Time, tesla@xxxxxxxxxx writes:

>I've not been as successful.  I've been trying the circuit on a .35
>A Oriental synchronous (reaction) motor with a variety of capacitor
>sizes, though, and at best can only achieve 15 degrees of
>change.  My variac is a small one, with inductance tuning from 0 to
>400 nH ... I can generally use less than 100 nH before I lose synch
>on the motor.   I've followed John's advice to look for the cap that
>provides around 3-5 volt rise on the motor usage (somewhere around
>3-4 microF) but to no avail. And I've tried cap sizes ranging from 1
>microF to around 50 microF.   Has anyone had a similar experience
>with the circuit ... there don't seem to be too many parameters to
>adjust, and with so many success stories, I wonder if it is not just
>one of the idiosyncrasies of this particular motor.
>Chris Westland


A number of us have used that motor with the phase shifter and
it worked well.  I assume you're still also using the additional
capacitor that comes with the motor in its original circuit
location.  It may be a good idea to increase the value of that
cap also, but this may depend on the weight of the rotor.
The motor comes
with a 2uF cap I think.  So that could be increased to
4uF.  Then the phase shift cap should be added in it's
proper circuit location.  If the rotor is too heavy, it may
interfere with the operation maybe, since this is a small
weak motor in general.  I seem to remember that I used
3 or 4uF for the phase shift cap when I tested this type
of motor with the phase shifter circuit.  I show a rotary on
my website which uses this type of motor.  It's the motor
I used for the phase shifter tests for that motor type.
This motor was for 1800rpm use.  Some of the motors
are marked for both 1500 or 1800rpm (50 or 60Hz).
Actually they should both work fine on either frequency
for our purposes.  Do I understand correctly that you're
not seeing any resonant rise above line voltage at any
time across the motor input terminals as the variac knob
is rotated along it's range, no matter what value cap
you choose for the phase shifter cap?  If so, that is
mysterious to me.

I show the MiniSync Rotary at my website which uses
this type of Oriental motor.  In this case I was able to
get by with a smaller than normal run capacitor to save
space.  I think I used 1uF instead of 2uF.




J. Christopher Westland, PhD CPA
Professor, ISMT, University of Science & Technology, HK Clearwater Bay,Kowloon, Hong Kong
Tel: 852 2358 7643
Fax: 852 2358 2421
Mob: 852 9528 1745
URL: ihome.ust.hk/~westland
Mobile e-mail: chris.westland@xxxxxxxxxxxx