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@
DC 260-360V is input ot power module and power module switches power supply current according to rotation
position of magnet 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)
\* At point F: U* is chopped (OFF), V' is ON (circuit in Fig. 3-4)
Upper arm
transistor
=
:
Lower arm
Ep
:
transistor
'
Fig.
3— 2
Switching order of power module
.
e
Time T in Fig. 3-2 shows the switching period, and relation with rotation speed (N)of the compressor is
shown by formula below;
N = 60/2 X 1/T
¢
Fig. 3-3 shows voltage waveform at each point shown in Figs. 3-1 and 3-4.
nae
U* transistor chopped
U: transistor ON
@® and
260V-360V — f-
| Chopping period
a
Chopping period (313 yx sec.)
Upper arm transistor
Current at
©:
Fig.
3— 3
Voltage waveform at each point
@
When power is supplied:U* — U', because of that U* is chopped, current flows as shown below;
ey
(1)
When U*- transistor is ON: .U* transistor > U coil + V coil > V- transistor ~ DC current detection.
~
resistor > Point ® (Fig. 3-1)
;
oh
(2)
When Us+ transistor is OFF: (by inductance of motor coil) U coil + V coil + V- transistor + Return diode
~+ Point ® (Fig. 3-4)
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