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4300C User Manual
b) Using a Shorting Switch
When using a shorting switch instead of the 4300C flyback diode, the
current stored in the inductor discharges through the cables and switch.
The current discharges with a time constant calculated from the formula
below which is dependent on the test current that was used to charge
the inductor:
Test Current Discharge Time
Range Used: (in Seconds):
10 Amps 7 x L ÷ R
1 Amp 5 x L ÷ R
.1 Amp 2 x L ÷ R
< .1 Amp Not required
Where:
L = Inductance in Henries
R =Total resistance of cables, switch and inductor (in ohms)
In a typical application R might be approximately 1 milliohm (.001Ω) and
L might be 1000 Henries. If the 10 amp range of the 4300C was used to
measure the inductor, 7,000,000 seconds are required (11½ weeks) to
discharge it. The 4300C may be disconnected at any time provided the
short circuit is maintained across the winding.
9-4
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