Optimal Voltage Control; Elimination Of Electrical Noise; Ipm; Function Of Main Parts - Mitsubishi Electric MSH09TW Service Manual

4. Elimination of electrical noise

Noise filter circuit is formed by L61, 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 prevents it from reaching
outside of the unit.

5. 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.

10-10-3. Function of main parts

SYMBOL
C61 POWER FACTOR CAPACITOR
SMOOTHING CAPACITOR
C62, C63
CT61, CT62 CURRENT TRANSFORMER
DS61 DIODE STACK
DS62 DIODE STACK
IPM INTELLIGENT POWER MODULE
L REACTOR
L61 COMMON MODE CHOKE COIL
R
CURRENT-LIMITING RESISTOR
X64 RELAY

10-11. Optimal voltage control

The purpose of optimal voltage control is to operate the compressor at optimal
voltage that meets the load detected by the power factor of the compressor.
1. Optimal
As shown on the right the efficiency (ratio of output against input) of the
motor in the compressor becomes optimal when the sliding (ratio of differ-
ence between the actual number of rotation and the number of synchronous
rotation of motor) is one fixed value. The value of sliding can be calculated
from the power factor since the sliding and the power factor are mutually
related as shown in the table on the right. To make the value of sliding so
that the efficiency of motor is optimal, the power factor of the compressor is
detected. Then the detected power factor is controlled so that its efficiency
can be high. As a result, it is possible to operate the compressor at optimal
voltage.
2. How to determine the optimal voltage
Compare the detected power factor with the target power factor so that the efficiency of motor is optimal, the voltage
correction value is changed and the optimal output voltage is determined.
Optimal output voltage[V]= Standard voltage at certain frequency [V]x voltage correction value(%)
Target power factor minus detected power factor
(Calculated value is supposed to be "A".)
-2%<A<+2%
NAME
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 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.
A[-2%
A]+2%
FUNCTION
1
Calculation of voltage
correction value (%)
Previous voltage correction value minus 1
Same as previous voltage correction value
Previous voltage correction value plus 1
66
Power factor
slip
efficiency
0