Mitsubishi Electric MSC-GE-VB Service Manual page 19

Input current waveform without PAM
Due to the time of no electricity;
• Power factor gets worse.
• Harmonic gets increased.
Input voltage
No electricity runs into
diode module because the
voltage at both sides of smoothing
capacitor is higher than input voltage.
4. Intelligent power module
INTELLIGENT POWER MODULE consists of the following components
• IGBT (x6)
• Drive Circuit
• Protection circuit
Since the above components are all integrated in INTELLIGENT POWER MODULE, INTELLIGENT POWER MODULE has a
merit to make the control circuit simplify and miniaturize.
5. Elimination of electrical noise
NOISE FILTER CIRCUIT, which is formed by *CMC COILS capacitors placed on P.C. board, eliminates electrical noise of AC
power that is supplied to main power supply circuit. And this circuit prevents the electrical noise generated in the inverter cir-
cuit from leaking out.
*CMC COILS: Common mode choke coils
MUZ-FD50,GE60/71
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 are placed in sub circuit.
2. At normal operation
When AC runs into noise fi lter P.C. board, its external noise is eliminated in NOISE FILTER CIRCUIT.
After noise being eliminated from AC, it is rectifi ed to DC by REACTOR and POWER FACTOR CORRECTION MODULE. If
the operating frequency becomes 25 Hz or more, DC voltage rises to 370 V.
DC voltage, to which has AC been rectifi ed by process
TELLIGENT POWER MODULE.
The DC (Bus voltage), which has been stabilized in process
MODULE and 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. Power factor improvement
Booster coil reactor and POWER FACTOR CORRECTION MODULE rectify AC to DC and control its voltage.
In the motor drive system of sine wave control, power factor can be improved by reducing harmonics. POWER FACTOR COR-
RECTION MODULE and reactor stabilize the voltage of DC supplied to inverter circuit and make its waveform smooth.
4. Intelligent power module
INTELLIGENT POWER MODULE consists of the following components.
• Power Transistors (x6) : Converts DC waveform to 3-phase AC waveform and outputs it.
• Drive Circuit
• Protection circuit
Since the above components are all integrated in INTELLIGENT POWER MODULE, INTELLIGENT POWER MODULE has a
merit that can get the control circuit simplifi ed and miniaturized.
5. Elimination of electrical noise
NOISE FILTER CIRCUIT, which is formed by *CMC COILS and capacitors placed on the noise fi lter P.C. board, eliminates
electrical noise of AC power that is supplied to main power supply circuit. In short, common mode noise is absorbed in this circuit.
Moreover, normal mode noise is absorbed in another NOISE FILTER CIRCUIT which is formed by *NMC COILS and capacitors.
Both NOISE FILTER CIRCUITS exist for preventing the electrical noise generated in the inverter circuit from leaking out.
*CMC COILS: Common mode choke coils
*NMC COILS: Normal mode choke coils
Input current
Energized time is short in
case L inductance is small.
: Converts DC waveform to 3-phase AC waveform and outputs it.
: Drives transistors.
: Protects transistors from overcurrent.
: Drives transistors.
: Protects transistors from over current.
Input current waveform with PAM
Owing to the increase of energized time;
• Power factor gets better.
• Harmonic gets suppressed.
Release of energy stored in L.
Compulsory energizing
by switching.
, is stabilized by SMOOTHING CAPACITOR and supplied to IN-
, is converted to 3-phase AC by INTELLIGENT POWER
19
Peak gets down.
Energized time is
extended by
optimization
of L inductance.