At Normal Operation; Power Factor Improvement Of Power Supply; Elimination Of Electrical Noise; Ipm - Mitsubishi Electric Mr.Slim MSZ09UN Service Manual

(2) At normal operation

Alternating current supplied from power supply is eliminated of any noise by L62(Common mode choke coil) and
L63 (Common mode choke coil). Then DS61(Diode stack) performs full-wave rectification of alternating current and
the alternating current is converted to direct current.
C63(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(Current-detecting resistor) is 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. C63 is used in this circuit to supply stable direct current voltage. However, in
case only C63 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), L61(Reactor) and DS62(Diode stack) to prepare the direct current circuit to extend the
period of the current running in the circuit.

3. Elimination of electrical noise

Noise filter circuit is formed by L62, L63, 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.
Symbol
Name
C61 POWER FACTOR CAPACITOR
C63 SMOOTHING CAPACITOR
CT61 CURRENT TRANSFORMER
DS61 DIODE STACK
DS62 DIODE STACK
IPM INTELLIGENT POWER MODULE
L61 REACTOR
L62 COMMON MODE CHOKE COIL
L63 COMMON MODE CHOKE COIL
R61 CURRENT-DETECTING RESISTOR
R64 CURRENT-LIMITING RESISTOR
X64 RELAY
It improves the power factor of power supply.
It stabilizes the direct current voltage.
It measures the current of main power supply circuit.
It converts the alternating current voltage to direct current voltage.
It is combined with L61 to improve the power factor of power supply.
It generates three-phase alternating current and operates compressor.
It is combined with DS62 to improve the power factor of power supply.
It eliminates and absorbs the electrical noise.
It eliminates and absorbs the electrical noise.
It detects the current and protects the compressor and IPM.
It absorbs the rush current so not to run into the main power supply
circuit when the electricity is turned on.
It short-circuits the circuit to current-limiting resistor when the
compressor operates.
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Function