Linde T20 SP - Page 88

Service Training
Section 6
Page 34
6.3.3 Starting the controller LES
The LES steering is the main safety unit, if it has broken down, the truck is stopped and no more operation
is authorised (lifting included).
Procedure for start-up: (the steps written enable quick diagnostics during breakdown)
- Starting the LES after the key in inputs 3X1: 1 / 18 / 19 =>+24V.
the supply negative is directly in input 3X1: 11 => -Ub
- The LES generates a stabilised voltage on the outputs 3X1: 20/21 => +8.2V for the positiveand for the
outputs 3X1: 2/12 => -Ub for the negative
- The steering controls the proper operation of the 2 set value and wheel potentiometers by the double
signals (redundant potentiometers) in inputs 3X1: 3/4 and 3X1: 13/22 => 4.1V (voltages measured
when the set value and the wheel are in the alignment of the fork arms).
- The LES controls a first safety internal relay (A), this relay provides the supply positive in output 3X1
: 10 =>+24V (for the line contactor 3K1) and a negative via a Mosfet transistor in output
3X1: 9 => -Ub (for the line contactor 3K1)
- The steering contactor 3K1 and the wheel brake system coil (F.V.) 7A5 are then fed.
The power stage is controlled, motor at stop, outputs:M1 and :M2 => 12V
The brake pivot is then controlled in current (between 5 and 750 mA), if the harness breaks, the truck
is brought to a halt by the CAN BUS link.
- The LES gives the two traction operation activation signals:
The steering controls the second safety relay (B) giving the positive for the traction (input positive 1X1:
1 for the internal relay contact to the LAC) in output 3X1:29 => +24V and a negative signal of OK
controlled by a Mosfet in output 3X1: 8 => -Ub
6.3.4 Validation of the traction and the hydraulic
For safety reasons, the validation of the traction and the hydraulic is done with two different signals, one,
positive coming from the safety relay B of the LES that supplies the line contactor of the traction and
hydraulic, the other, negative is controlled by a transistor giving the steering status to the LAC controller.
Then a final traction authorisation is sent by the LES via the CAN BUS, this authorisation only pertains to
the traction.
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