![]() Inductance does not affect the current as at constant source. With a linear DC source (as in the figure below), current is a function of just the winding resistance. Unlike pure resistive loads for DC motors, the resistance, inductance and back EMF on the rotor windings are deciding factors in optimizing PWM frequency and duty cycle. Hence, the output torque, which is linearly proportional to the average winding current, can be correctly controlled in coreless motors. Using PWM allows precise current control in the windings. This lets them be used in applications needing dynamic behavior and fast responses from the motor. However, properly designed PWM minimizes eddy current effects and improve how the motors are driven.Ĭore-less brushed DC motors have low inertia and inductance. One trade-off of using PWM with a motor are the eddy current losses in the rotor windings due to the continuous PWM switching which, in general, are not present in linear power sources. The better efficiency of the PWM drive increases battery life and reduces heating in electronic components. PWM voltage regulation, on the other hand, is efficient and can be used effectively with battery or DC power-driven applications. Moreover, in battery-driven applications, it is impractical to use linear regulation at varying load points. Linear regulation is generally inefficient and a requires a larger housing. This can be done by a continuous linear regulation power supply or pulse width modulation (PWM). Running a motor at usable load points requires a variable, controllable power source. Many applications using miniature brushed DC motors require motors to operate at more than one load point or through specific load cycles. ![]()
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