Low Power Factors and Higher Rated Motors

Smaller motors are, by their nature, less efficient and will have lower

power factors and total efficiency ratings.

Thanx

But what sort of nature ?

technical reason?

Regards

Specific magnetic loading for small motor w.r.t rating is higher than large motor, which in turn is responsible for p.f rating.

The Actual power consumed by induction motor consists of
Active (true or real) power (measured in kilowatts, kW) and
Reactive power - the nonworking power caused by the magnetizing current, required to operate the device (measured in kilovars, kVAR)
the KVAR depends on power factor.Now power factor depends on cosine of lagging or leading phase angle which in turn depends on Inductance or capacitance of the circuit. So the power factor of the motor depends on the design factor of the motor big or small.
Actual power of 3 Phase motor = √ 3 E x I CosΦ

Cos Φ ( Power Factor ) = Actual Power / √ 3 E x I

This equation is a numerical method of expressing the phase difference between voltage and current in a motor circuit. The current in an induction motor lags the applied voltage, and only the component that is in phase with the voltage varies with motor power. The relationship expressed in the above equation can be shown as a vector relationship in which the numerical expression is actually the cosine of the angle Ø. So in practical design conditions motors of larger power have better pf compared small motors.