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Now, if this motor is fed with current of 2 A and assuming that back-EMF is exactly 2 V, it is rotating at 7200 rpm and the mechanical power is 4 W, and the force on rotor is = N or 0.0053 N. The torque on shaft is 0.0053 N⋅m at 2 A because of the assumed radius of the rotor (exactly 1 m).
If a mechanical system has no losses, then the input power must equal the output power. This provides a simple formula for the mechanical advantage of the system. Let the input power to a device be a force F A acting on a point that moves with velocity v A and the output power be a force F B acts on a point that moves with velocity v B.
For an electric motor, the efficiency, represented by the Greek letter Eta, [49] is defined as the quotient of the mechanical output power and the electric input power, [50] calculated using this formula:
It developed remarkable mechanical output power. His motor set a world record, which Jacobi improved four years later in September 1838. [21] His second motor was powerful enough to drive a boat with 14 people across a wide river. It was also in 1839/40 that other developers managed to build motors with similar and then higher performance.
The ideal mechanical advantage is the ratio of the force out of the machine (load) to the force into the machine (effort), or =. Applying the constant power relationship yields a formula for this ideal mechanical advantage in terms of the speed ratio:
Mechanical power: P = W = J s −1: M L 2 T ... The mechanical work done by an external agent on a system is equal to the change in kinetic energy of the system ...
Nameplates on electrical motors show their power output, not the power input (the power delivered at the shaft, not the power consumed to drive the motor). This power output is ordinarily stated in watts or kilowatts. In the United States, the power output is stated in horsepower which, for this purpose, is defined as exactly 746 W. [21]
In mechanical engineering, mechanical efficiency is a dimensionless ratio that measures the efficiency of a mechanism or machine in transforming the power input to the device to power output. A machine is a mechanical linkage in which force is applied at one point, and the force does work moving a load at another point.