Mitsubishi Electric MSC-GE-VB Service Manual page 18

MUZ-FD50, GE60/71
NOISE
POWER
FILTER
SUPPLY
CIRCUIT
Function of main parts
NAME
INTELLIGENT POWER MODULE
SMOOTHING CAPACITOR
CURRENT TRANSFORMER
REACTOR
POWER FACTOR CORRECTION MODULE
RESISTOR
RELAY
2-8-2. Outline of main power supply circuit
MUZ-GC, HC, FD25/35, GE25/35/42/50, EF
1. At the start of operation
Main power supply circuit is formed when RELAY is turned ON at COMPRESSOR startup.
To prevent rush current from running into the circuit when power supply is turned ON, RESISTOR is placed in sub circuit.
2. At normal operation
When AC runs into P.C. board, its external noise is eliminated in the NOISE FILTER CIRCUIT.
After noise is eliminated from AC, it is rectifi ed to DC by DIODE MODULE 1.
DC voltage, to which AC has been rectifi ed by process
TELLIGENT POWER MODULE.
DC voltage, which has been stabilized in process
supplied to COMPRESSOR.
3. Purpose of PAM adoption
PAM: Pulse Amplitude Modulation
PAM has been adopted for the effi ciency improvement and the adaptation to IEC harmonic current emission standard.
Outline of simple partial switching method
In conventional inverter models, DIODE MODULE rectifi es AC voltage to DC voltage, SMOOTHING CAPACITOR makes its DC
waveform smooth, and INTELLIGENT POWER MODULE converts its DC voltage to imitate AC voltage again in order to drive
the compressor motor.
However, it has been diffi cult to meet IEC harmonic current emission standard by above circuit because harmonic gets gener-
ated in the input current waveform and power factor gets down. The simple partial switching method with PAM, which has been
adopted this time, places and utilizes BOOSTER CHOPPER CIRCUIT before rectifying AC voltage in the general passive-meth-
od converter circuit. As harmonic gets suppressed and the peak of waveform gets lower by adding BOOSTER CHOPPER CIR-
CUIT as mentioned above and by synchronizing the timing of switching with the zero-cross point of waveform, the input current
waveform can be improved and the requirement of IEC harmonic current emission standard can be satisfi ed. Since the switching
is synchronized with the zero cross point, this simple partial switching method has the feature of lower energy loss compared to
active fi lter method. In addition, output and effi ciency is enhanced by combining with vector-controlled inverter in order to boost
the voltage of power supplied to INTELLIGENT POWER MODULE.
REACTOR
POWER
RESISTOR
FACTOR
CORRE-
CTION
MODULE
RELAY
It supplies 3-phase AC power to compressor.
It stabilizes the DC voltage and supplies it to INTELLIGENT POWER MOD-
ULE.
It measures the current of the compressor motor.
It rectifi es AC, controls its voltage and improves the power factor of power
supply.
It absorbs the rush current not to run into the main power supply circuit when
the power is turned ON.
It keeps the RESISTOR, which restricts rush current, short-circuit while the
compressor is operating.
P
+
SMOOTHING
CAPACITOR
N
INTELLIGENT
POWER
MODULE
, is stabilized by SMOOTHING CAPACITOR and supplied to IN-
, is converted to 3-phase AC by INTELLIGENT POWER MODULE and
18
CURRENT
TRANSFORMER
U
U
MS
V
3~
V
W
W
COMPRESSOR
FUNCTION