{ "cells": [ { "cell_type": "markdown", "metadata": {}, "source": [ "# CHAPTER 46 : ELECTRONIC CONTROL OF A.C MOTORS" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "## EXAMPLE 46.1 , PAGE NO :- 1827" ] }, { "cell_type": "code", "execution_count": 3, "metadata": { "collapsed": false }, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "Ton = 1.89 ms.\n", "magnitude of the current pulse I0 = 102.31 A.\n" ] } ], "source": [ "'''The wound-rotor induction motor of Fig.43.5 is rated at 30-kW,975 rpm,440-V,50 Hz.The open-circuit line voltage is 400V and the load\n", "resistance is 0.5 ohm.If chopper frequency is 200 Hz,calculate Ton so that the motor develops a gross torque of 200 N-m at 750 rpm.Also,\n", "calculate the magnitude of the current pulses drawn from the capacitor.'''\n", "\n", "import math as m\n", "Ns = 1000.0 #rpm (Synchronus speed)\n", "N1 = 750.0 #rpm (rotating speed)\n", "E2 = 400.0 #V (OC line voltage)\n", "Tg = 200.0 #N-m (gross torque)\n", "R0 = 0.5 #ohm (load resistance)\n", "f = 200.0 #Hz (chopper frequency)\n", "s = (Ns-N1)/Ns # slip\n", "Vrl = s*E2 #V (rotor line voltage)\n", "Vdc = 135.0 #V (DC voltage of 3-phase bridge rectifier)\n", "#Now, Tg = P^2/(2*3.14*Ns).Therefore,\n", "P2 = Tg*2*3.14*Ns/60 #W\n", "#Power dissipated as heat\n", "sP2 = s*P2 #W\n", "#Power is actually dissipated in R and is equal to rectifier output Vdc*Idc.Therefore,\n", "Idc = sP2/Vdc #A\n", "#The apparent resistance at the input of chopper is\n", "Ra = Vdc/Idc #ohm\n", "#Now, Ra = Ro/(f*Ton)^2 .Therefore,\n", "Ton = m.sqrt(R0/(f*f*Ra))*1000 #ms\n", "#Current in R0 can be found from relation,I0^2*R0 = sP2\n", "I0 = m.sqrt(sP2/R0) #A\n", "print \"Ton = \",round(Ton,2),\"ms.\"\n", "print \"magnitude of the current pulse I0 =\",round(I0,2),\"A.\"" ] }, { "cell_type": "code", "execution_count": null, "metadata": { "collapsed": true }, "outputs": [], "source": [] } ], "metadata": { "kernelspec": { "display_name": "Python 2", "language": "python", "name": "python2" }, "language_info": { "codemirror_mode": { "name": "ipython", "version": 2 }, "file_extension": ".py", "mimetype": "text/x-python", "name": "python", "nbconvert_exporter": "python", "pygments_lexer": "ipython2", "version": "2.7.11" } }, "nbformat": 4, "nbformat_minor": 0 }