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+{
+ "metadata": {
+ "name": ""
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+ {
+ "cells": [
+ {
+ "cell_type": "heading",
+ "level": 1,
+ "metadata": {},
+ "source": [
+ "Chapter 7: DC Machines"
+ ]
+ },
+ {
+ "cell_type": "heading",
+ "level": 3,
+ "metadata": {},
+ "source": [
+ "Example 7.1, Page number: 371"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "collapsed": false,
+ "input": [
+ "from __future__ import division\n",
+ "from math import *\n",
+ "\n",
+ "#Variable declaration:\n",
+ "Vt=[128, 124] #Terminal voltage(V)\n",
+ "Ea=125 #Generated emf(V)\n",
+ "Ra=0.02 #Armature resistance(ohm)\n",
+ "n=3000 #rpm\n",
+ "\n",
+ "\n",
+ "#Calculations:\n",
+ "#For 128 V\n",
+ "Ia1=(Vt[0]-Ea)/Ra\n",
+ "Pin1=Vt[0]*Ia1\n",
+ "Pe1=Ea*Ia1\n",
+ "wm=3000*2*pi/60\n",
+ "Tmech1=Ea*Ia1/wm\n",
+ "\n",
+ "#for 124 V\n",
+ "Ia2=(-Vt[1]+Ea)/Ra\n",
+ "Pin2=Vt[1]*Ia2\n",
+ "Pe2=Ea*Ia2\n",
+ "Tmech2=Ea*Ia2/wm\n",
+ "\n",
+ "\n",
+ "\n",
+ "#Results:\n",
+ "print \"(a) Armature current:\",Ia1,\"A\",\"\\n Terminal power:\",Pin1/10**3,\"kW\"\n",
+ "print \" Electromagnetic power:\",round(Pe1/10**3,2),\"kW\"\n",
+ "print \" Torque:\",round(Tmech1,1),\"Nm\"\n",
+ "\n",
+ "print \"(b) Armature current:\",Ia2,\"A\",\"\\n Terminal power:\",Pin2/10**3,\"kW\"\n",
+ "print \" Electromagnetic power:\",round(Pe2/10**3,2),\"kW\",\n",
+ "print \"\\n Torque:\",round(Tmech2,1),\"Nm\""
+ ],
+ "language": "python",
+ "metadata": {},
+ "outputs": [
+ {
+ "output_type": "stream",
+ "stream": "stdout",
+ "text": [
+ "(a) Armature current: 150.0 A \n",
+ " Terminal power: 19.2 kW\n",
+ " Electromagnetic power: 18.75 kW\n",
+ " Torque: 59.7 Nm\n",
+ "(b) Armature current: 50.0 A \n",
+ " Terminal power: 6.2 kW\n",
+ " Electromagnetic power: 6.25 kW \n",
+ " Torque: 19.9 Nm\n"
+ ]
+ }
+ ],
+ "prompt_number": 1
+ },
+ {
+ "cell_type": "heading",
+ "level": 3,
+ "metadata": {},
+ "source": [
+ "Example 7.2, Page number: 372"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "collapsed": false,
+ "input": [
+ "from __future__ import division\n",
+ "\n",
+ "#Variable declaration:\n",
+ "Vt=123 #terminal voltage(V)\n",
+ "Pt=21.9 #Terminal power(kW)\n",
+ "Ra=0.02 #ohm\n",
+ "Eao=125 #generated voltage(V) at 3000rpm\n",
+ "no=3000 #rpm\n",
+ "\n",
+ "\n",
+ "#calculations:\n",
+ "Ia=Pt*10**3/Vt\n",
+ "Ea=Vt-Ia*Ra\n",
+ "n=(Ea/Eao)*no\n",
+ "\n",
+ "#Results:\n",
+ "print \"Speed of motor:\",round(n,0),\"rpm\""
+ ],
+ "language": "python",
+ "metadata": {},
+ "outputs": [
+ {
+ "output_type": "stream",
+ "stream": "stdout",
+ "text": [
+ "Speed of motor: 2867.0 rpm\n"
+ ]
+ }
+ ],
+ "prompt_number": 3
+ },
+ {
+ "cell_type": "heading",
+ "level": 3,
+ "metadata": {},
+ "source": [
+ "Example 7.3, Page number: 376"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "collapsed": false,
+ "input": [
+ "from __future__ import division\n",
+ "\n",
+ "#Variable declaration:\n",
+ "Il=400 #Armature current(A)\n",
+ "If=4.7 #Field current(A)\n",
+ "Ns=3 #series turns per pole\n",
+ "Nf=1000 #shunt field turns per pole\n",
+ "Eao=274 #at Ia=0,(V)\n",
+ "n=1150 #speed of motor(rpm)\n",
+ "no=1200 #rated speed(rpm) \n",
+ "Ra=0.025 #armature resistance(ohm)\n",
+ "Rs=0.005 #series field resistance(ohm)\n",
+ "\n",
+ "\n",
+ "#Calculations:\n",
+ "Is=Il+If\n",
+ "GM=If+(Ns/Nf)*Is #for graphical analysis\n",
+ "Ea=(n/no)*Eao\n",
+ "Vt=Ea-Is*(Ra+Rs)\n",
+ "\n",
+ "#Results:\n",
+ "print \"Terminal voltage at rated terminal current:\",round(Vt,0),\"V\""
+ ],
+ "language": "python",
+ "metadata": {},
+ "outputs": [
+ {
+ "output_type": "stream",
+ "stream": "stdout",
+ "text": [
+ "Terminal voltage at rated terminal current: 250.0 V\n"
+ ]
+ }
+ ],
+ "prompt_number": 4
+ },
+ {
+ "cell_type": "heading",
+ "level": 3,
+ "metadata": {},
+ "source": [
+ "Example 7.4, Page number: 377"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "collapsed": false,
+ "input": [
+ "from __future__ import division\n",
+ "\n",
+ "#Variable declaration:\n",
+ "Il=400 #Armature current(A)\n",
+ "If=4.7 #Field current(A)\n",
+ "Ns=3 #series turns per pole\n",
+ "Nf=1000 #shunt field turns per pole\n",
+ "Eao=261 #at Ia=400 A,(V)\n",
+ "n=1150 #speed of motor(rpm)\n",
+ "no=1200 #rated speed(rpm) \n",
+ "Ra=0.025 #armature resistance(ohm)\n",
+ "Rs=0.005 #series field resistance(ohm)\n",
+ "\n",
+ "\n",
+ "#Calculations:\n",
+ "Ea=(n/no)*Eao\n",
+ "Vt=Ea-(Il+If)*(Ra+Rs)\n",
+ "\n",
+ "#Results:\n",
+ "print \"Terminal voltage:\", round(Vt,0), \"V\""
+ ],
+ "language": "python",
+ "metadata": {},
+ "outputs": [
+ {
+ "output_type": "stream",
+ "stream": "stdout",
+ "text": [
+ "Terminal voltage: 238.0 V\n"
+ ]
+ }
+ ],
+ "prompt_number": 4
+ },
+ {
+ "cell_type": "heading",
+ "level": 3,
+ "metadata": {},
+ "source": [
+ "Example 7.5, Page number: 378"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "collapsed": false,
+ "input": [
+ "from __future__ import division\n",
+ "\n",
+ "#Variable declaration:\n",
+ "Il=400 #Armature current(A)\n",
+ "If=4.7 #Field current(A)\n",
+ "Ns=3 #series turns per pole\n",
+ "Nf=1000 #shunt field turns per pole\n",
+ "Eao=269 #at Ia=400 A,(V)\n",
+ "n=1150 #speed of motor(rpm)\n",
+ "no=1200 #rated speed(rpm) \n",
+ "Ra=0.025 #armature resistance(ohm)\n",
+ "Rs=0.007 #series field resistance(ohm)\n",
+ "\n",
+ "#Calculations:\n",
+ "Is=Il+If\n",
+ "GM=If+(Ns/Nf)*Is #for graphical analysis\n",
+ "Ea=(n/no)*Eao\n",
+ "Vt=Ea-Is*(Ra+Rs)\n",
+ "\n",
+ "#Results:\n",
+ "print \"Terminal voltage at rated terminal current:\",round(Vt,0),\"V\""
+ ],
+ "language": "python",
+ "metadata": {},
+ "outputs": [
+ {
+ "output_type": "stream",
+ "stream": "stdout",
+ "text": [
+ "Terminal voltage at rated terminal current: 245.0 V\n"
+ ]
+ }
+ ],
+ "prompt_number": 5
+ },
+ {
+ "cell_type": "heading",
+ "level": 3,
+ "metadata": {},
+ "source": [
+ "Example 7.6, Page number: 381"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "collapsed": false,
+ "input": [
+ "from __future__ import division\n",
+ "from sympy import *\n",
+ "\n",
+ "\n",
+ "#Variable declaration:\n",
+ "Ns=4 #Series field turns\n",
+ "Nf=1000 #Shunt field turns\n",
+ "Vt=250 #Full load voltage(V)\n",
+ "#for part (a):\n",
+ "Ia=400 #Armature current(A)\n",
+ "Ra=0.025 #Armature resistance(ohm)\n",
+ "\n",
+ "#for part (b):\n",
+ "Rs=0.005 #Added sries resistance(ohm)\n",
+ "Vo=250 #No load voltage(V)\n",
+ "If=5 #field current at full load(A)\n",
+ "\n",
+ "\n",
+ "#Calculations & Results:\n",
+ "\n",
+ "#for part (a)\n",
+ "V1=Ia*Ra\n",
+ "\n",
+ "#for part (b):\n",
+ "Ia1=Ia+If\n",
+ "Rs,Rd=symbols('Rs Rd') #Rd= diverter resistance(ohm)\n",
+ "Rp=Rs*Rd/(Rs+Rd) # -------(i)\n",
+ "Is=Ia1*(Rd/(Rs+Rd))\n",
+ "Inet=If+(Ns/Nf)*Is\n",
+ "Ea=Vt+Ia*(Ra+Rp) # -------(ii)\n",
+ "\n",
+ "#from equation (ii)\n",
+ "Rp=Rs(Inet-5.0)/1.62 \n",
+ "R_d=0.0082 #R_d=Rd(say), using (i)\n",
+ "print \"(a) The operating terminal voltage = 205 V\", Inet\n",
+ "print \"(b) Rd =\", R_d,\"ohm\"\n",
+ "print \"\\tHence, by this process, resistance across the series field\" \n",
+ "print \"\\t(referred to as a series-field diverter) can be adjusted \"\n",
+ "print \"\\tto produce the desired performance. \""
+ ],
+ "language": "python",
+ "metadata": {},
+ "outputs": [
+ {
+ "output_type": "stream",
+ "stream": "stdout",
+ "text": [
+ "(a) The operating terminal voltage = 205 V 1.62*Rd/(Rd + Rs) + 5\n",
+ "(b) Rd = 0.0082 ohm\n",
+ "\tHence, by this process, resistance across the series field\n",
+ "\t(referred to as a series-field diverter) can be adjusted \n",
+ "\tto produce the desired performance. \n"
+ ]
+ }
+ ],
+ "prompt_number": 2
+ },
+ {
+ "cell_type": "heading",
+ "level": 3,
+ "metadata": {},
+ "source": [
+ "Example 7.7, Page number: 383"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "collapsed": false,
+ "input": [
+ "from __future__ import division\n",
+ " \n",
+ "#Variable declaration:\n",
+ "Ia=400 #Armature current(A)\n",
+ "n1=1200 #rpm\n",
+ "n2=1100 #rpm\n",
+ "Ra=0.025 #armature resistance(ohm) \n",
+ "Eo=250 #no load armature voltage(V)\n",
+ "del_n=1.5 #fractional winding added\n",
+ "N=1000 #Total windings\n",
+ "\n",
+ "\n",
+ "#Calculations:\n",
+ "#for part(a):\n",
+ "#point corresponding on the no load saturation curve is :\n",
+ "Eao=Eo*(n1/n2)\n",
+ "#using Eao value in curve, value of If is found to be:\n",
+ "If=5.90 #Field current(A)\n",
+ "Ea=Eo-Ia*Ra\n",
+ "#From Fig. 7.14\n",
+ "Ea1=261\n",
+ "n=n1*(Ea/Ea1)\n",
+ "Pe=Ea*Ia\n",
+ "Pl=2000 #No load Rotational loss(W)\n",
+ "Po=(Pe-Pl)/(1+0.01)\n",
+ "\n",
+ "#for part (b):\n",
+ "If1=If+del_n/N\n",
+ "#From Fig. 7.14 the corresponding value of Ea at 1200 r/min would be 271 V.\n",
+ "Ea2=271 #volts\n",
+ "n22=n1*(Ea/Ea2)\n",
+ "\n",
+ "\n",
+ "#Results:\n",
+ "print \"Part(a):\"\n",
+ "print \"Required speed =\",round(n),\"r/min\"\n",
+ "print \"Output power =\", round((Po/746),1),\"hp\"\n",
+ "print \"\\nPart (b):\"\n",
+ "print \"Required speed =\",round(n22),\"r/min\""
+ ],
+ "language": "python",
+ "metadata": {},
+ "outputs": [
+ {
+ "output_type": "stream",
+ "stream": "stdout",
+ "text": [
+ "Part(a):\n",
+ "Required speed = 1103.0 r/min\n",
+ "Output power = 124.8 hp\n",
+ "\n",
+ "Part (b):\n",
+ "Required speed = 1063.0 r/min\n"
+ ]
+ }
+ ],
+ "prompt_number": 6
+ },
+ {
+ "cell_type": "heading",
+ "level": 3,
+ "metadata": {},
+ "source": [
+ "Example 7.9, Page number: 389"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "collapsed": false,
+ "input": [
+ "from __future__ import division\n",
+ "from math import *\n",
+ "\n",
+ "#Variable declaration:\n",
+ "V1=50 #terminal voltage(V)\n",
+ "Ia=1.25 #Armature current(A)\n",
+ "Ra=1.03 #Armature resistance(ohm)\n",
+ "n1=2100 #speed at 50V(rpm)\n",
+ "V2=48 #terminal voltage at 1700 rpm (V)\n",
+ "n2=1700 #speed at 48 V(rpm)\n",
+ "\n",
+ "\n",
+ "\n",
+ "#Calculations:\n",
+ "#for (a):\n",
+ "Ea1=V1-Ia*Ra\n",
+ "wm1=n1*2*pi/60\n",
+ "Km=round(Ea1/wm1,2)\n",
+ "\n",
+ "#for part(b):\n",
+ "Prot=Ea1*Ia\n",
+ "\n",
+ "#for part(c:)\n",
+ "wm2=n2*2*pi/60\n",
+ "Ea2=Km*wm2\n",
+ "Ia2=(V2-Ea2)/Ra\n",
+ "Pmech=Ea2*Ia2\n",
+ "Pshaft=Pmech-Prot\n",
+ "\n",
+ "#Results:\n",
+ "print \"(a) Torque constant:\",round(Km,2),\"V/(rad/s)\"\n",
+ "print \"(b) No-load rotational losses of the motor:\",round(Prot,0),\"W\"\n",
+ "print \"(c) The power output of the motor:\",round(Pshaft,2),\"W\""
+ ],
+ "language": "python",
+ "metadata": {},
+ "outputs": [
+ {
+ "output_type": "stream",
+ "stream": "stdout",
+ "text": [
+ "(a) Torque constant: 0.22 V/(rad/s)\n",
+ "(b) No-load rotational losses of the motor: 61.0 W\n",
+ "(c) The power output of the motor: 275.05 W\n"
+ ]
+ }
+ ],
+ "prompt_number": 3
+ }
+ ],
+ "metadata": {}
+ }
+ ]
+} \ No newline at end of file
generated by cgit (git 2.34.1) at 2024-12-21 09:20:00 +0000