I am using two 40 Amp variacs, one to limit the current and one as
voltage control. I have wired them up as follows: The current control
variac is in series with the input of the voltage variac (this variac
has been cut to act as a variable inductor, 0.4 to 27.8mH) and the
other end of the voltage variac is connected to the neutral; the brush
is the output to my transformer. The problem is that when I turn on
the mains, the voltage variac makes a buzzing sound (obviously mains
frequency) and the ammeter is reading 10 Amps.
Which ammeter, where?
How is the 'variable inductor' set?
What load, if any on the 'voltage variac'?
I think that the core is saturating.
Which core? The 'voltage variac'?
However, if I remove the current control variac and
connect the input of the voltage variac to another variac controlled
power supply, so that the input to the variac in question is supplied
via the brush output of the power supply variac
How is the 'power supply' variac set?
there is only a quiet hum from the variac
Which 'the variac'?
and the ammeter is reading about 0.5 Amps.
Which 'the ammeter', where?
What is wrong and how do I fix the problem?
Is anything 'wrong'?
(Yes: thats a lot of questions. It can be hard to
troubleshoot by text, without diagrams.)
Might try using the 40 A 'inductor variac'
A 40A variac has a lowish 'impedance' (since its
designed for high current.). It may not be
limiting as anticipated.
best
dwp
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