PPT Slide
For a DC series motor, the following data are given: supply voltage = 440 V., duty cycle = 30%, motor circuit inductance = 0.04 H., maximum allowable change in armature current = 8 A. Determine the chopper frequency.
Section 13.10: Speed Control of DC Motors cont.
The average voltage across the motor is Vave. = aVt = 0.3´440V. = 132 V.
The voltage across the motor circuit inductance is Vt - Vave. = 440V. - 132V. = 308 V. = 0.04H.´8A./ton = LDi/Dt (mimicking Ldi/dt) which yields …
But a = ton/T \ T = ton/a = 1.04 ms/0.3 = 3.46 ms so that the frequency is …
f = 1/T = 1/(3.46ms) = 289 pulses per second