BEHLMAN BL10000 Series, User'S Manual And Technical Reference Manual

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SECTION 5
THEORY OF OPERATION
5.1 GENERAL
5.1.1 The BL series represents low cost, high performance, AC to AC power invertors. These units provide
variable output voltage and frequency from 0 to 135 Vac and 45 to 500 Hz respectively. This series may be
operated from a 120/208 Vac, 220/380 Vac 277/480 Vac, 200 Vac (Delta), or 346/600 Vac 2 phase or 120Vac
or 240Vac single phase input line at 50 or 60 Hertz. Other versions include higher single phase outputs and
external step-up/down output transformer options.
5.2 INPUT POWER
5.2.1 The BL series models consist of two basic sections, and input power chassis (DC power supply) and
an inverter/control chassis. The incoming line voltage is connected to the input chassis where it is applied to
a multi-pulse transformer/rectifier system. The output of the rectifier circuit is applied to a large bank of
electrolytic capacitors to provide the required filtering. The output of the power chassis is a bipolar DC voltage
of +/-250 Vdc centered around the circuit common. Additional circuitry is incorporated to provide in rush current
limiting and overload protection.
5.2.2 In rush surge limiting is provided by placing large power resistors in series with two of the input phase
voltages and the power chassis transformer primary. During power up, these resistors limit the current surge
to the filter capacitor bank. Once full voltage is reached, a relay is used to bypass the limiting resistors allowing
normal operation.
5.2.3 Over current protection of the DC supply is provided by the multi-pole input circuit breaker. Additional
protection is provided by fast acting semiconductor fuses located in the control chassis.
5.2.4 The output of the power chassis is available at a rear panel mounted terminal block. Connection to the
control chassis is afforded by supplied jumper cables. Note that the length of these cables is somewhat critical.
Do not substitute with long cables.