Regulating System; Le/Lf/Lt2 Up To -7 With Dol Starter (Fig. 1.10); Le/Lt5 Up To -20, Lf5 Up To -10, Each With Y/D Starter (Fig. 1.11) - Atlas Copco LE2 Instruction Book

Instruction book

1.3 Regulating system

1.3.1 LE/LF/LT2 up to -7 with DOL starter (Fig. 1.10)

The regulating system includes:
- Check valve (CV)
- Air pressure switch (MDR) with pressure release valve (2) and on/off switches (5).
Operation
Air pressure switch (MDR) opens and closes its contacts at pre-set pressures. During loaded operation,
the contacts are closed: the motor is running.
When the pressure in the air receiver reaches the pre-set maximum pressure, the contacts as well as
pressure release valve (2) are opened. The motor stops, the air at the delivery side of the compressor is
vented to atmosphere and check valve (CV) closes to prevent venting of the receiver.
When the pressure in the air receiver decreases to the pre-set minimum pressure, the contacts of the air
pressure switch close and pressure release valve (2) closes. The motor restarts and compressed air is
supplied to the receiver again.

1.3.2 LE/LT5 up to -20, LF5 up to -10, each with Y/D starter (Fig. 1.11)

The regulating system includes:
- Electric cubicle (11)
- Air pressure switch (MDR)
- On/off switch (5)
- Solenoid valve (Y1)
- Unloader (UA) with integrated check valve (CV)
Operation
Air pressure switch (MDR) opens and closes its contacts at pre-set pressures. During loaded operation,
the contacts are closed: the motor is running and solenoid valve (Y1) is energized preventing the
compressed air from flowing to unloader (UA).
When the pressure in the air receiver reaches the pre-set maximum pressure, the contacts of pressure
switch (MDR) open. The motor stops and solenoid valve (Y1) is de-energized. Compressed air from the
receiver will flow via the solenoid valve to plunger (12) which causes unloading valve (UV) to open. The
air at the delivery side of the compressor is blown through silencer (9) to atmosphere and check valve
(CV) closes to prevent venting of the receiver.
When the pressure in the air receiver decreases to the pre-set minimum pressure, the contacts of the
pressure switch close. The motor restarts and, after switching over from star to delta, solenoid valve (Y1)
is energized. Control air from the unloader plunger chamber is vented to atmosphere. Unloading valve
(UV) closes and compressed air is supplied to the receiver again.
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