Zapi EPS-AC, Operating And Users Manual, Page: 5 / 52

Page 5
1.2 STEER ANGLE POSITION POTENTIOMETER
To execute an automatic centering operation, a multiturn 5K potentiometer must be
mounted directly on the end of the output shaft of the steering gear reduction box. This
potentiometer measures the angle of the MDU directly. The full range of possible output
is approximately 0÷5Vdc. This potentiometer also provides information for the steer
angle indicator gauge mounted on the operator console.
1.3 OPERATOR CONSOLE
The control unit can support the following devices typically fixed on the operator conso-
le.
1) Key switch
2) Manual/automatic centering selection switch (AUTOSEL).
3) A status device (BUZZER).
4) A steer angle indicator gauge.
1.4 AC STEERING SERVO MOTOR
The steering system includes a three phase AC induction motor with a maximum rated
power of:
1) 40A current rating (Imax=70A) if the battery voltage is 36Vdc or less. (about 1KW
rated power motor at Vbatt=36V).
2) 30A current rating (Imax=70A) if the battery voltage is 48Vdc. (about 1KW rated
power motor).
3) 22A current rating (Imax=50A) if the battery voltage is greater than 48Vdc. (about
1.2KW rated power motor at Vbatt=80V).
The gear box should be chosen so that the complete 180° MDU rotation takes 3 to 6
seconds at the maximum steer speed.
1.5 STEERING HANDLE
This is a multi-turn steering handle or wheel attacched to a command device. There are
two option:
1) tacho-generator. This solution requires just a two wire connection. The
recommended tacho-generator is AIRPAX Part N° 24Vdc - 9904 -120 - 16206.
2) stepper motor. This solution requires either a six wire connection or an optional
three wire connection. The recommended stepper motor model is Minebea type
code AA23KM-K227-T20V.
This last device requires a frictional linkage because there is no gear box.
Mounting the command device to eliminate axial or radial loading on the input shaft is
important for reliable operation.
Note: the logic card for the tacho-generator and for the stepper motor applications are
different. So a different order code must be specified.