MPE DP SERIES II, Руководство по эксплуатации и обслуживанию

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6.0 PRINCIPLE OF OPERATION
6.1 General
Figure 6.1 illustrates the block diagram of the DP Series power supply. As illustrated, DP Series
power supplies are comprised of master/slave modules. Master/slave modules have a power
ratings of 5 kW, 10 kW, or 15 kW to produce 10 kW, 20 kW, or 30 kW system output,
respectively.
DP Series power supplies have a number of feedback loops to insure balance between modules.
The details of the modules are described below.
6.2 Master Module
Power is fed through ac fuses and is distributed to the driver board, inrush limiter, and main 3ö
contactor. The driver board contains a switching power supply and supplies power to the other
printed circuit boards in the system. The inrush limiter is a step start device which is used to
initially charge capacitors on the input dc bus and limit the inrush of current. The inrush limiter is
initiated when the power supply is switched from a standby to a power state. After the charge
cycle, the main 3ö contactor is energized and power is allowed to flow to the load. The optional
EMI filter filters common mode and differential mode noise emanating from the supply.
Output power is controlled through a polyphase chopper. For the 15 kW master module, three
choppers, phased 120° apart, provide a current source to a current fed inverter. The 10.0 kW
master module uses two choppers, phased 180° apart, and the 5.0 kW master module uses only one
chopper. The choppers are controlled with current mode, pulse width modulation (PWM). This
modulation scheme provides a quick response for transients and filtering harmonics on the dc bus.
As illustrated, chopper output current is monitored for balancing and for sensing overload current
conditions. The polyphase chopper has been engineered to eliminate harmonic components
minimizing currents circulating in the power supply.
The polyphase chopper produces a controlled dc bus which is connected to dc link inductors and
current fed, IGBT medium frequency link inverter. The inverter, which operates at 400 Hz to 600
Hz, excites the main transformer at higher than normal line frequencies. This operation produces
ohmic isolation between the input and output of the power supply using a transformer of
dramatically reduced size.
The inverter operates with a 50% duty cycle and its frequency of operation is transparent to the
performance of the power supply.
The output of the main power transformer is converted to dc via rectifiers. Low voltage versions
of the DP Series power supply use midpoint diode configurations and higher voltage versions use
bridge configurations.
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