What is a hydraulic motor and how does it convert hydraulic energy to mechanical power?

• A. A device that converts fluid pressure and flow into rotational torque and shaft power.
• B. A device that stores hydraulic energy.
• C. A valve that modulates flow.
• D. A sensor that measures pressure.

Answer: (A)

A hydraulic motor converts hydraulic energy into mechanical power by using the pressure and flow of fluid to produce rotational motion on a shaft. When high-pressure fluid enters the motor, it acts on internal elements such as pistons, vanes, or gear teeth. This forces those elements to push and turn, generating torque that drives the output shaft. The speed of rotation depends on how much fluid is flowing (the flow rate), while the amount of torque depends on the pressure driving that flow. In simple terms, hydraulic power equals pressure times flow, and the shaft power equals torque times angular speed (minus losses). So the motor is turning hydraulic energy into usable mechanical work.

Other devices mentioned don’t directly convert hydraulic energy into rotation: an accumulator stores energy, a valve modulates flow, and a sensor measures pressure.