EHA-PAM-291-A-20 Vickers

Product Description:

The EHA-PAM-291-A-20 is an electronic power-amplifier module produced by Vickers within the EHA Power Supplies series. Installed between a PLC or analogue controller and a proportional solenoid, the unit translates low-level command voltages into controlled current, allowing hydraulic valves to follow reference signals accurately in industrial automation systems. It occupies minimal panel space thanks to a moulded housing and supports plug-in terminal wiring for quick field replacement.

At power-up the amplifier applies a dither amplitude of 4% to the output current, and this micro-oscillation, combined with the built-in dither frequency of 400 Hz, helps overcome spool friction in proportional valves. Signal gain is preset to 4 mA/V, so a 5 V reference produces 20 mA, while the zero is fixed at an offset of 0 mA to keep the valve closed when no command is present. The high-impedance input of 47 kΩ prevents loading of the upstream controller. The power stage can deliver up to 200 mA, covering most Vickers proportional coils, and the housing made of Polyamid 6.6 withstands oil mist and vibration on mobile equipment. Test terminal E scales 1 V to 500 mA and terminal F scales 1 V to 2.5 % amplitude, allowing technicians to verify current loop and dither level during service.

Both the supply and the drive-enable lines expect a nominal 24 V DC source; within this range the circuitry draws only 7 W, so cabinet heat rise is low. The regulator tolerates a maximum supply ripple of 4 Vpp, maintaining stable coil current even on vehicle batteries or poorly filtered power buses. Protection class IP20 indicates finger-safe terminals but requires installation inside an enclosure; the 0.11 kg mass permits DIN-rail mounting without additional support. Input impedance and gain already discussed are complemented by the internal test scaling, giving maintenance staff direct readout without breaking the loop.