Hitachi RAS-25QH1 Technische Information Seite 173

12V p=) Reset circuit er al
Reset signa!
@
Peak current cut off cc Trip signal synthesis a
circuit circuit (acme
Chopper signal 3
a
E
8
DC380V
wenn
E
ee
e
5
module
8 3
5
8
=>
([_
> (Compresso
3
8 /
motor
£
a
DC current level
(AX-8H20)
Voltage amp. circuit
Gina
signal
S)
© SS Detection
resistor
DC current
Fig. 9-2
@ The following describes the operations of each circuit in detail.
9.1. Peak current cut off circuit
Fig. 9-3 shows the peak current cut off circuit and the waveforms at each section.
Reset voltage
24A 4
Voltage at point @):
1.2V0 Ot
To drive circuit
ene ee De
1 1
Micro computer '
' :
:
Voltage at pin@9) !
f
i Detectio
Vottage at point © i resistor
Fig. 9-3 Peak Current Cut off Circuit and Waveforms at Each Section
@ The Ip cut off circuit detects an instantaneous high-level current and stops the inverter to protect
components including the power module.
@ lf acurrent exceeding 24A flows as shown in the diagram, the voltage at point @ detected by the
detection resistor is input to the positive © terminal of COM(A), and when it exceeds the voltage at the
negative © terminal which is the set value, the output pin voltage (at point ®) of COM(A) goes "LO" >
*HI". This turns Q3 on and stops the power module circuit via D4 and D2; also the voltage at point ©
goes "HI" "LO" and the Ip signal is supplied to pin @ of the micro computer which stops the inverter.
@ On the other hand, since the voltage at the positive © terminal is pulled up by R4, it is higher than the
voltage at the negative © terminal even after the DC current becomes OA and the voltage at point @
returns to OV, therefore the output is temporarily kept at "Hi (memory function).
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