8
B. Discharge Circuit
The discharge circuit, which provides the magnetizing current, consists of an electrically
matched Parallel SCR Assembly (
1SCR
), Parallel SCR Driver Board (
4PCB
), Reverse
Current Blocking Diode Assembly (
1DDP
), and the Magnetizing Fixture. Provided the
Capacitor Bank is charged to the preset voltage level and the Magnetize function has been
initiated, the Control Circuitry sends a logic signal to the Parallel SCR Driver Board. This
circuit board gates both SCRs with a conditioned signal allowing the stored energy in
Capacitor Bank to discharge through the Magnetizing Fixture. The Reverse Current
Blocking Diode provides a circulation path for the collapsing current preventing any
reverse current from flowing through the Magnetizing Fixture.
C. Current Bias Supply
The current bias supply is used when the Magnetizing Fixture is a Current Transformer.
This supply provides current in the primary windings of the Current Transformer. The
direction of current is reverse to that of the magnetizing current. This is to bias the steel
core if the transformer magnetically so that the greatest possible flux change may be
transferred from primary to secondary. This supply consists of transformer (
2T
), rectifier
diode (
11D
), filter capacitor (
10C
), inductor (
3L
), and resistor (
7R
).
D. Safety Drain Circuit
The safety drain circuit will safely discharge the energy storage capacitor bank when the
power to the machine is turned off or the Magnetizing Fixture is disconnected. Once the
discharging of the capacitor bank begins, the machine will not operate until the voltage
has decreased to a safe level. The drain circuit consists of a high voltage vacuum relay
(
CRD
) and associated capacitors (
12C, 13C, and 14C
) and diodes (
12D and 13D
), two
10 K ohm 50 watt resistors (
3R and 4R
), and lockout relay (
1CR
). The contacts of the
vacuum relay are normally closed and will connect the 10K resistors across the capacitor
bank when the relay is not powered. The capacitors on the vacuum relay’s coil provide a
delay of about 4 seconds before the relay will turn off so that momentary interruptions of
power will not effect machine operation. Once the draining of the capacitors begins
lockout relay (
1CR
) engages and its contacts open removing power to the charge push
button.
Содержание 942B
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