Motor Mechanical Power

Formula

Description

Mechanical power output of a motor is the product of torque and angular velocity. This is the rotational analog of linear power P = F × v. To convert from RPM to rad/s, multiply by 2π/60. For example, a motor spinning at 3000 RPM has ω = 314.16 rad/s. If it produces 0.5 N·m of torque, the mechanical output power is 157 W. The electrical input power is higher than this due to losses (copper losses in windings, iron losses in the core, friction, and windage), with typical motor efficiencies ranging from 60-95% depending on the motor type and size.

Variables

• P — Mechanical power output (W)
• τ — Torque (N·m)
• ω — Angular velocity (rad/s)

Practical Notes

1 horsepower ≈ 746W. DC motor power curves show that torque is maximum at stall (zero speed) and zero at no-load speed, while power peaks at approximately half the no-load speed. BLDC and stepper motors have different torque-speed characteristics. Always check that the motor driver can supply the stall current without damage.