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Re: solid state coil problem
From: RODERICK MAXWELL[SMTP:tank-at-mail.magnolia-dot-net]
Reply To: tank-at-mail.magnolia-dot-net
Sent: Sunday, November 09, 1997 10:04 PM
To: tesla-at-pupman-dot-com
Subject: solid state coil problem
I have finaly gotten my solid state coil driver up and running. But I,m
running into a problem when it comes to the amount of current the
transistors are drawing. When power is first applied with the variac the
current surges up to about 30 amps then drops down to about 12. Thats
okay, but the voltage applied at this point is only 24 volts! I,ve tried
resistors, decreasing the duty cycle, and increasing the freq. but
nothing seems to help. The reistors eat up all the power and generate a
lot of heat. Decreasing the duty cycle only helps a little. And
increasing the freq. in hopes of getting more inductive reactance only
generates more heat in the switching transistors, and increases current
draw.
The output transfomer has been wound in push-pull configuration. The
two switching transistors are IRF450. The freq. range is from 135khz to
222khz. The inductance from each leg to the center tap is 135uH. The
signal generator is a SG3525A pulse width modulator. And the driver is
an SG3626R dual high speed driver.
Does any one know how to limit the current to the output transformer?
I was thinking that maybe you could use another inductor of much higher
value in series with the transformer to limit current?
Frankensteins Helper
Max