Mitsubishi MSZ-FA-VA Service Technical Manual page 64

Rotor
Rotor Position Signal
w In brushless DC motor, permanent magnet is embedded in the rotor. Therefore, it doesn't require energy to excite the rotor
like AC motor does. However, it's necessary to control the frequency of three-phase AC current supplied to the stator
according to the polar direction of magnet embedded in the rotor so as to drive the motor efficiently. Controlling three-phase
AC current frequency also means controlling the timing to switch the polarity of stator. Therefore, the polar direction of rotor
needs to be detected.
4-1-1-4. Control Method of Rotation Times
Sine wave control makes the current transformers conduct real time detection of the value of the current running into the motor,
locates the rotor position from the detected value, and decides if voltage should be impressed and if frequency should be chan-
ged.
Compared to the conventional control and rotor position detection method, sine wave control can provide finer adjustment of the
voltage of supplied power. The value of the current running into the motor is determined by each motor characteristic.
4-1-2. MXZ-3A54VA
MXZ-4A71/80VA
4-1-2-1. Iverter main power supply circuit
NOISE
POWER
N/F
SUPPLY
Function of main parts
SYMBOL
IPM INTELLIGENT POWER MODULE
CB1~3 SMOOTHING CAPACITOR
CT1~2 CURRENT TRANSFORMER
CT61
CURRENT TRANSFORMER
L
REACTOR
PFC
POWER FACTOR CONTROLLER
R64A, R64B
CURRENT-LIMITING RESISTOR
X64
RELAY
4-1-2-2. Outline of main power supply circuit
1. At the start of operation
Main power supply circuit is formed when X64 (Relay) is turned ON at compressor startup.
To prevent rush current from running into the circuit when power supply is turned ON, R64A and R64B
(Current-limiting resistor) are placed in sub circuit.
2. At normal operation
1 When AC runs into noise filter P.C. board, its external noise is eliminated in the noise filter circuit.
2 After noise being eliminated from AC, it is rectified to DC by L (Reactor) and PFC (Power factor controller). If the operating
frequency becomes 25Hz or more, DC voltage rises to 370V.
3 DC voltage, to which has AC been rectified by process 2, is stabilized by CB1~3 (Smoothing capacitor) and supplied to
IPM (Intelligent power module).
4 The DC (Bus voltage), which has been stabilized in process 3, is converted to three-phase AC by IPM and supplied to
compressor.
5 CT1 and CT2 (Current Transformer), which are placed in the power supply circuit to compressor, are used to measure the
value of phase current and locate the polar direction of rotor with algorithm. PWM (Pulse width modulation) controls impre-
ssed voltage and frequency with those information.
Downloaded from AC-Manual.com Manuals
Permanent magnet is embedded.
Necessary
FILTER P. C. BOARD
R64A/R64B
X64
CT61
NAME
DC Motor
POWER BOARD
L
+CB1
PFC
It supplies three-phase AC power to compressor.
It stabilizes the DC voltage.
It measures the current of the compressor motor.
It measures the current of the main power supply circuit.
It rectifies AC, controls its voltage and improves the power factor of
power supply.
It restricts rush current with the resistance.
It short-circuits the resistance which restricts rush current during the
compressor operates.
64
AC Motor
Excited by magnetic field of stator
Unnecessary
V
MC
CT1
U
U
CB2
CB3
IPM
V
CT2
W
FUNCTION
W