Simrad ROBERTSON AP45 manual J45A Electronic Junction Unit, J45A principle

Page 3-6	Robertson AP45 Autopilot
	Design and theory of operation

J45A Electronic Junction Unit

The J45A operates reversible hydraulic power units with variable speed control (RPU80, RPU160, RPU200 and HLD2000) and reversible electro mechanical power units (MRD100). The unit consists of a printed circuit board with terminal block, fuse, motor drive electronics and reversing relay mounted in the same type of aluminium cabinet as the J45S.

Rudder commands from AP45 Control Unit to IC3 A and B makes the relay RL1 change the polarity to the motor. IC2A ensures the motor brake is switched on by T2 when there is no rudder commands from AP45. IC2A also controls a “dead time” (delay) to ensure the RL1 relay contacts have physically changed position before voltage is applied to the motor. This prevents arcing of relay contacts.

Adjusting RV1, preset speed, the output pulse width is decreased/increased, hence the voltage (RMS) to the motor is changed, adjustable 0-12V.

Connecting straps S1 and S2 provides adjustable 0-24V output for 24V drive units.

Connecting an external strap from terminal 2 to 4 will enable a “Soft start” function, which reduces the start current and is recommended for the most powerful drive units like RPU200, RPU300, HLD2000LD and MRD100.

Fig. 3-8

J45A principle

Simrad Robertson AS

Egersund - Norway