Document: MAN00238A
Page 16 of 28
R:\Documents\MAN Manuals\MAN00238A BRC-15-1111R-STD-J37.doc
6.2
Power Card 853189539P
AC power is connected to a three phase bridge rectifier circuit. See Figure 3. The rectifiers power a
raw capacitive filter. The inverter switches, in a full bridge configuration, alternate the high voltage
transformer primary winding between the rail voltages established by the raw supply capacitors,
producing a bipolar square wave signal on the primary winding.
-
RAIL
FILTER
SEC
PRI
+
RAIL
AC
INVERTERS
Figure 3 – Power Inverter Simplified Diagram
The inverter switches are IGBTs that are gated ‘ON’ for an interval established by the pulse width
modulator chip on the Regulator card. At power turn-on, the raw capacitor bank is charged through
rectifier CR12 and current limited by R42 and R43. When the initial charge period is complete,
relay K1 is energized, connecting the rail capacitors to the low impedance three-phase line.
The inverter IGBTs do not operate until the raw capacitors are charged, K1 is energized, and the
‘HV ON’ pushbutton is depressed. The IGBT gate signal originates on the Regulator board as
varying width pulses at a fixed frequency. The frequency is determined by R219 and C133 on the
Regulator board.
