Atlas Copco XAS 175 Dd, Instruction Manual

Page: 15 / 34

I
NSTRUCTION
M
ANUAL
15
2.8.2 D
ESCRIPTION
Operation of the electric circuit
1. Closing ON/OFF switch (S1) supplies voltage to:
– charging indicator lamp (H1), which lights up
– fuel level gauge (P1)
– relay (K6), which makes contact (30-87), closing the line
between switch (S2) and starter solenoid (K0)
– alarm lamp (H6), which lights up.
2. Depressing override/start switch (S2) supplies voltage to:
– engine stop solenoid (Y1) and hour meter (P3), which
respectively open the engine fuel supply and start
counting
– starter solenoid (K0) via relay (K6) contact (30-87).
Solenoid (K0) engages the starter motor (M1), which
cranks the engine.
3. When alternator (G1) starts charging, its built-in voltage
regulator de-energises relay (K6) and extinguishes lamp
(H1).
Relay (K6) makes contact (30-87a), opening the line to
solenoid (K0), the contact of which opens and disengages
starter motor (M1).
4. After the engine oil pressure has built up sufficiently,
engine oil pressure switch (S5) closes its contact,
energising relay (K1).
Relay (K1) makes contact (30-87). Lamp (H6) goes out.
5. Releasing override/start switch (S2) interrupts overriding of
the shut-down circuit. Solenoid (Y1), hourmeter (P3) and
relay (K1) remain energised over relay (K1) contact (30-87)
and over relay (K6) contact (30-87a).
Engine safety shut-down
1. If engine oil pressure shut-down switch (S5) or compressor
temperature shut-down switch (S7) opens, relay (K1) will
be de-energised, breaking contact (30-87) and making
contact (30-87a).
The engine stop solenoid (Y1) is released, the engine
stops and alarm lamp (H6) lights up.
2. The same happens in the event engine temperature switch
(S14), V-belt failure switch (S15) or fuel level switch (B6)
closes, but in this case relay (K8) is energised and its
contact (30-87a) breaks the circuit to relay (K1).
3. Circuit breaker (F1) will cut out if an overload occurs in the
engine stop solenoid circuit or in case of short circuit. It
can be reset after a short period of cooling off by pressing
its push button.