Hitachi RAS-25QH1 Technische Information Seite 163

Voltage at point ®
600mV
a
Voltage at point ©
'
'
'
'
4
1
'
f
'
,
'
1
Voltage at point O:
Fig. 6-4 Rotor Magnetic Pole Position Detecting Circuit and Waveforms of Voltages at Each Point
@ The motor induced voltage signal (the voltage at point @) is passed through a lowpass filter
consisting of R101, R104 and C101 and its phase is shifted by 90 ° to create a triangular signal. The
signal is then passed through a highpass filter consisting of C104-C106 to remove DC bias components
from this triangular signal, thus producing the voltage at point ©.
@ The motor induced voltage signal is a signal which indicates the rotor's magnetic pole position. When
the motor load, that is the load current, increases, the phase of this signal advances from that of the
rotor's magnetic pole position and the operation with the correct timing cannot be done which decreases
efficiency. Therefore the position detection signal is corrected by the micro computer to prevent the
efficiency from decreasing.
@ PS-HIC compares the voltages at points ® and © to create the voltage at point ©.
@ The voltage at point © is input to the outdoor micro computer and the switching from the C" transistor
to the A~ transistor is timed by its leading edge and the switching from the C' transistor to the A'
transistor is timed by its trailing edge.
@ Other phases are shifted by 120° from each other.
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