Intelligent power module switches power supply current according to position of the compressor motor
rotor.
The switching order is as shown in Fig. 3-2.
At point E : U
+
is ON, V
–
is ON (circuit in Fig.
––
3-1)
is ON (circuit in Fig.
is ON (circuit in Fig.
At point F : U
+
is chopped (OFF), V
–
is ON (circuit in Fig.
––
3-4)
is ON (circuit in Fig.
is ON (circuit in Fig.
N = 60/2 X 1/T
Fig. 3-3 shows voltage waveform at each point shown in Figs. 3-1 and 3-4. First half of upper arm is
chopper, second half is ON, and first half of lower arm is chopper, second half is ON.
U
–
diode
––
→
Point A (Fig. 3-4)
When power is supplied U
+
→
V
–
, because of that U
+
is chopped, current flows as shown below;
(1) When U
+
transistor is ON: U
+
transistor
→
U coil
→
V coil
→
V
–
transistor
––
→
DC current
detection resistor
→
Point B (Fig. 3-3)
(2) When U
+
transistor is OFF: (by inductance of motor coil) U coil
→
V coil
→
V
–
transistor
––
→
V
Time
W
T
V
U
V
Upper arm
transistor
Lower arm
transistor
W
W
U
E F
E F
+
+
W
W
+
+
-
-
VV
-
Fig. 3-2 Switching order of power module
Fig. 3-3 Voltage waveform at each point
U transistor chopped
Chopping period (208µ sec.)
Chopping period
T
transistor ON
◯
◯
◯
◯
◯
◯
U
280V-300V
Voltage at
VV
Upper arm transistor
Upper arm transistor
Upper arm transistor
Upper arm transistor
Current at
ON
+
-
Upper Upper arm transistor is controlled to ON/OFF by 2.5kHz - 5kHz chopper signal. Rotation speed of
the compressoris proportional to duty ratio (ON time/ ON time + OFF time) of this chopper signal.Time
T in Fig. 3-2 shows the switching period, and relation with rotation speed (N) of the compressor
isshown by formula below;
Table 3-1
Ip (peak current cut)
LD301 Blinks 2
times
Blinks 3
times
Blinks 4
times
LD301
LD301
Self-diagnosis
Self-diagnosis lamp
and mode
Abnormal low speed
rotation
Switching incomplete
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