Mitsubishi Electric MSC-GE-VB Service Manual page 25

MXZ-6C120VA
NOISE
POWER
FILTER
SUPPLY
CIRCUIT
Function of main parts
NAME
RESISTOR
RELAY
DIODE BRIDGE
REACTOR
SWITCHING POWER TRANSISTOR
DIODE
SMOOTHING CAPACITOR
POWER TRANSISTOR BRIDGE
CURRENT TRANSFORMER
3-1-2. Outline of main power supply circuit
MXZ-2B30VA MXZ-2B40VA MXZ-2B52VA
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 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.
CURRENT TRANSFORMER which is placed in the power supply circuit to COMPRESSOR, is used to measure the value
of phase current and locates the polar direction of rotor with algorithm. PWM (Pulse width modulation) controls impressed
voltage and frequency with those pieces of information.
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 generated 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-method converter circuit. As har-
monic gets suppressed and the peak of waveform gets lower by adding BOOSTER CHOPPER CIRCUIT as mentioned above and by syn-
chronizing 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 par-
tial 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
RESISTOR
+
RELAY
~ ~
-
DIODE
BRIDGE
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-circuited while
the compressor is operating.
It converts the AC voltage to DC voltage.
It improves power factor.
It controls the bus-bar voltage.
It stabilizes the DC voltage and supply it to INTELLIGENT POWER
MODULE.
It supplies 3-phase AC power to compressor.
It measures the current of the compressor motor.
+
SMOOTHING
CAPACITOR
DIODE
N
SWITCHING POWER
POWER TRANSISTER
TRANSISTOR BRIDGE
, is stabilized by SMOOTHING CAPACITOR and supplied to IN-
, is converted to 3-phase AC by INTELLIGENT POWER MODULE and
25
CURRENT
TRANSFORMER
P U
V
W
W
COMPRESSOR
POWER
MODULE
FUNCTION
U
MS
~
3