EHA-PAM-291-A-20 by Vickers

The EHA-PAM-291-A-20 is a compact DC supply module produced by Vickers and listed in the EHA Power Supplies series. Installed in machine panels, the EHA-PAM-291-A-20 converts and conditions direct current for proportional or on-off solenoids and other low-power automation loads. By maintaining regulated output current and providing factory-preset dither and gain adjustments, the module supports repeatable actuator response in hydraulic or pneumatic motion systems.

For line power, the module operates from a 24 V DC nominal input, and its factory dither amplitude is set to 4 %, which provides a small periodic modulation that helps minimize spool stiction in proportional valves. The built-in oscillator drives this waveform at 400 Hz, selected to stay outside audible ranges while avoiding resonance in hydraulic circuits. Current gain is preset to 4 mA/V, so a 5 V reference signal yields 20 mA of drive current. The input stage presents 47 k? impedance, allowing direct connection to standard PLC analog outputs without excessive loading. Under command, the power section can deliver up to 200 mA, which is adequate for most cartridge coils, and an offset of 0 mA means a zero command produces no residual current. The drive enable line accepts 24 V DC logic, and permissible supply ripple up to 4 Vpp allows the unit to tolerate noisy power buses.

Continuous power consumption is limited to 7 W, reducing cabinet heat rise, and the housing is molded from polyamide 6.6 for electrical insulation and impact resistance. The unit has an IP20 protection class, so it is intended for dry, clean locations and uses front screw terminals for wiring. A mass of 0.11 kg permits DIN-rail mounting without additional supports. Diagnostic test points are provided: terminal E outputs 1 V per 500 mA of load current, while terminal F produces 1 V per 2.5 % of dither amplitude, allowing calibration checks without breaking the circuit.