Main Power Supply Circuit; Outline Drawing Of Main Power Supply; Power Factor Improvement Of Power Supply; Elimination Of Electrical Noise - Mitsubishi Electric MSZ-G09SV Service Manual

9-22. Main power supply circuit

Outline drawing of main power supply

L61
POWER
SUPPLY
NOISE FILTER P.C. BOARD
1. Outline of main power supply circuit
(1) When the electricity is turned on to the outdoor unit
Rush current generates in the main power supply circuit.
To prevent the rush current from running into the main power supply circuit, R64A and R64B(Current-limiting
resistor) absorb the rush current.
After the rush current is absorbed, X64(Relay) is ON and the circuit to R64A and R64B are short-circuited, then the
electricity to R64A and R64b are bypassed.
Following the indoor unit's operation, X64 is switched to ON or OFF.
(2) At normal operation
Alternating current supplied from power supply is eliminated of any noise by L61(Common mode choke coil) and
L62 (Common mode choke coil). Then DS61(Diode stack) performs full-wave rectification of alternating current and
the alternating current is converted to direct current.
C62(Smoothing capacitor) stabilizes the power supply converted to direct current from alternating current and
supplies it to IPM(Intelligent power module).
Direct current rectified by DS61 is converted to three-phase alternating current by IPM. Microcomputer installed in
the electronic control P.C. board controls frequency and voltage of three-phase alternating current converted by
IPM.
Three-phase alternating current from IPM is supplied to the compressor with frequency and voltage decided by
microcomputer based on various kinds of information. R61 and R62(Current-detecting resistor) are installed for
overload protection of the compressor and for protection of IPM.
CT61(Current transformer) measures the current of main power supply circuit.

2. Power factor improvement of power supply

Unlike inverter-less alternating current circuit, the power factor of this inverter circuit is improved by extending the peri-
od of the current running in the circuit. C62 is used in this circuit to supply stable direct current voltage. However, in
case only C62 is used for stable supply of direct current, the power factor of power supply is lowered because the peri-
od of direct current running in the circuit is short. Therefore, for improvement of power factor, the circuit also uses
C61(Power factor capacitor), L(Reactor) and DS62(Diode stack) to prepare the direct current circuit to extend the peri-
od of the current running in the circuit.

3. Elimination of electrical noise

Noise filter circuit is formed by L61, L62, and the condenser installed on the noise filter P.C. board. It eliminates the
electrical noise (both common mode and normal mode noise) of alternating current power supply supplied to main
power supply circuit. Noise filter circuit also absorbs electrical noise that is generated in the inverter circuit and pre-
vents it from reaching outside of the unit.
4. IPM
Six power transistors that outputs the direct current waveform as three-phase alternating current waveform, the driving
circuit which operates the power transistors, and the overcurrent detecting circuit which protects the power transistors
are built into the IPM. It can simplify and miniaturize the control circuit.
R64AR64B
X64
CT61
L62
MICROPROCESSOR
ELECTRONIC CONTROL P.C. BOARD
DS62
DS61
L (~)
(+)
(–) (~)
(~)
(+)
(–) (~)
+
+
–
–
C62
C61
58
IPM
P
V
U
V
U W
W
R61
N
COMPRESSORE
R62