The pump-motor-valve assembly that generates and controls the oil flow driving a hydraulic elevator jack to raise and lower the car.
Full Definition
The hydraulic power unit (HPU) comprises an electric motor, hydraulic pump, oil reservoir, control valves, and pressure-limiting devices housed in a single cabinet usually located in a machine room adjacent to the hoistway. During ascent the motor drives the pump, forcing oil into the jack cylinder under pressure. Descent is typically gravity-driven through a controlled down valve. EN 81-20 §12 governs hydraulic elevator requirements including rupture valve response time (≤ 10 s), maximum system pressure, and fluid containment provisions to prevent environmental contamination.
