I got the Sidactors yesterday, Thanx Terry, and immediately took
action to measure their break over voltage.
Something soon seemed odd, they looked like TVS'es to me, not
sidactors at all.
When I applied voltage across them from my current limiting bench
supply, a HP6255a, the devices did respond to break over voltage, but
failed to break over to a near short, as advertised by Teccor, and as
previously experienced by the KxxxxF1 series that we have been using
up to now.
What I saw was a device that plainly clamped the voltage to the break
over level, and kept it there.
This is the behavior that I`d expect from a Zener and a TVZ, but not
from a Sidac.
Of course, there might be a limitation of my measuring approach that I
had overlooked, holding current came to mind, so I decided to lash up
a birds nest SISG, to test out the new types against a known good one,
the K2500F1, which has shown a consistent break over voltage of 135V
per section.
The K2500F1 single section worked as expected and produced this
oscilloscope trace:
http://www.hammertone.com/temp/sidac.jpg
In this screen,
http://www.hammertone.com/temp/sidac.jpg
Top trace, cyan CH2, is gate voltage, 15.2V
This is a bit low since generated from a 24V TVZ, but the current is
low too, as seen on 3rd trace.
2nd. trace, magenta CH3, is current into gate, measured with Tektronix
P6022 current clamp and passive terminator.
1.36A into gate.
3rd. trace, green CH4, is current in tank circuit, 17.8AP-P measured
with Pearson Current Monitor #101
4th trace, Yellow CH1, is voltage across tank cap., 135V
Screen says 62V but probe is MX9003 differential by Metrix in 200:1
So far so good.
But when I plug any of the following sidactors into this circuit, all
I can record is that the voltage across the cap rises to, and stays
at, break over voltage of device.
What I don`t see is any rapid discharge of tank capacitor, no voltage
rise on, or current into gate, and thus no oscillations.
So as far as I can see, these Sidactors are not what they are
advertised to be, but instead TVS, Zener whatever derivatives unsuited
for SISG duty.
I`m at my wits end with this, because -frankly- I feel out of my depth
claiming this in the face of a major manufacturer like Teccor.
I guess I's time to write them, but I'd just bring it up here first.
Cheers, Finn Hammer
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