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+{
+ "cells": [
+ {
+ "cell_type": "markdown",
+ "metadata": {},
+ "source": [
+ "# CHAPTER10 : PRINCIPLES OF DIRECT CURRENT MACHINES"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "metadata": {},
+ "source": [
+ "## Example E01 : Pg 394"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": 1,
+ "metadata": {
+ "collapsed": false
+ },
+ "outputs": [
+ {
+ "name": "stdout",
+ "output_type": "stream",
+ "text": [
+ "Induced emf = 205.2 V\n",
+ "Frequency of the rectangular voltage wave = 44.25 Hz\n"
+ ]
+ }
+ ],
+ "source": [
+ "# Example 10.1\n",
+ "# Computation of (a) Induced emf (b) Frequency of the rectangular voltage \n",
+ "# wave in the armature winding\n",
+ "# Page No. 394\n",
+ "# Given data\n",
+ "E1=136.8; # Generated emf\n",
+ "P=6.; # Number of poles\n",
+ "n=1180.; # Operating speed of machine\n",
+ "\n",
+ "# (a) Induced emf \n",
+ "\n",
+ "E2=E1*0.75*2.;\n",
+ "\n",
+ "# (b) Frequency of the rectangular voltage wave in the armature winding\n",
+ "\n",
+ "f=P*n*0.75/120.;\n",
+ "\n",
+ "# Display result on command window\n",
+ "print\"Induced emf =\",E2,\"V\"\n",
+ "print\"Frequency of the rectangular voltage wave =\",f,\"Hz\""
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "metadata": {},
+ "source": [
+ "## Example E02 : Pg 399"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": 2,
+ "metadata": {
+ "collapsed": false
+ },
+ "outputs": [
+ {
+ "name": "stdout",
+ "output_type": "stream",
+ "text": [
+ "Rheostat setting to obtain an induced emf of 290 V = 16.5662921348\n"
+ ]
+ }
+ ],
+ "source": [
+ "# Example 10.2\n",
+ "# Computation of rheostat setting required to obtain an induced emf of 290 V\n",
+ "# Page No. 399\n",
+ "# Given data\n",
+ "Ebat=240.; # Induced emf\n",
+ "If=8.9; # Field current\n",
+ "Rf=10.4; # Field resistance\n",
+ "\n",
+ "# Rheostat setting required to obtain an induced emf of 290 V\n",
+ "\n",
+ "Rrheo=(Ebat/If)-Rf;\n",
+ "\n",
+ "# Display result on command window\n",
+ "print\"Rheostat setting to obtain an induced emf of 290 V =\",Rrheo"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "metadata": {},
+ "source": [
+ "## Example E03 : Pg 401"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": 3,
+ "metadata": {
+ "collapsed": false
+ },
+ "outputs": [
+ {
+ "name": "stdout",
+ "output_type": "stream",
+ "text": [
+ "No-load voltage if the voltage regulation is 2.3 percent = 245.52 V\n"
+ ]
+ }
+ ],
+ "source": [
+ "# Example 10.3\n",
+ "# Computation of no-load voltage if the voltage regulation is 2.3 percent\n",
+ "# Page No. 401\n",
+ "# Given data\n",
+ "Vrated=240.; # Rated voltage\n",
+ "VR=0.023; # Voltage regulation\n",
+ "\n",
+ "\n",
+ "# No-load voltage if the voltage regulation is 2.3 percent\n",
+ "\n",
+ "Vnl=Vrated*(1.+VR);\n",
+ "\n",
+ "# Display result on command window\n",
+ "print\"No-load voltage if the voltage regulation is 2.3 percent =\",Vnl,\"V\""
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "metadata": {},
+ "source": [
+ "## Example E04 : Pg 405"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": 4,
+ "metadata": {
+ "collapsed": false
+ },
+ "outputs": [
+ {
+ "name": "stdout",
+ "output_type": "stream",
+ "text": [
+ "Percentage reduction in field flux = -47.4191394394 Percent\n"
+ ]
+ }
+ ],
+ "source": [
+ "# Example 10.4\n",
+ "# Computation of percentage reduction in field flux required to obtain a \n",
+ "# speed of 1650 r/min while drawing an armature current of 50.4 A.\n",
+ "# Page No. 405\n",
+ "# Given data\n",
+ "VT=240.; # Induced emf\n",
+ "R=95.2; # Shunt field resistance\n",
+ "IT=72.; # Total current\n",
+ "Ra=0.242; # Armature resistance\n",
+ "Ia2=50.4; # Armature current\n",
+ "n1=850.; # Rated speed of shunt motor\n",
+ "n2=1650.; # Speed of armature winding\n",
+ "\n",
+ "\n",
+ "# Percentage reduction in field flux\n",
+ "\n",
+ "If1=VT/R; # Field current\n",
+ "Ia1=IT-If1; # Armature current\n",
+ "Ea1=VT-Ia1*Ra; # Armature emf\n",
+ "Ea2=VT-Ia2*Ra;\n",
+ "phip2=(n1/n2)*(Ea2/Ea1);\n",
+ "PerRed=(phip2-1.)*100.;\n",
+ "\n",
+ "\n",
+ "\n",
+ "# Display result on command window\n",
+ "print\"Percentage reduction in field flux =\",PerRed,\"Percent\""
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "metadata": {},
+ "source": [
+ "## Example E05 : Pg 408"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": 5,
+ "metadata": {
+ "collapsed": false
+ },
+ "outputs": [
+ {
+ "name": "stdout",
+ "output_type": "stream",
+ "text": [
+ "No-load speed = 1820.0 r/min\n"
+ ]
+ }
+ ],
+ "source": [
+ "# Example 10.5\n",
+ "# Computation of no-load speed\n",
+ "# Page No. 408\n",
+ "# Given data\n",
+ "nrated=1750.; # Rated speed\n",
+ "SR=4.; # Speed regulation\n",
+ "# No-load speed\n",
+ "Snl=nrated*(1+SR/100);\n",
+ "# Display result on command window\n",
+ "print\"No-load speed =\",Snl,\"r/min\""
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "metadata": {},
+ "source": [
+ "## Example E06 : Pg 418"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": 6,
+ "metadata": {
+ "collapsed": false
+ },
+ "outputs": [
+ {
+ "name": "stdout",
+ "output_type": "stream",
+ "text": [
+ "Induced emf = 265.0 V\n"
+ ]
+ }
+ ],
+ "source": [
+ "# Example 10.6\n",
+ "# Computation of Induced emf\n",
+ "# Page No. 418\n",
+ "# Given data\n",
+ "P=25000.; # Power of the generator\n",
+ "VT=250.; # Rated voltade of the machine\n",
+ "Ra=0.1053; # Armature resistance\n",
+ "Rip=0.0306; # Resistance of interpolar winding\n",
+ "Rcw=0.0141; # Resistance of compensating windings\n",
+ "# Induced emf\n",
+ "Ia=P/VT; # Armature current\n",
+ "Racir=Ra+Rip+Rcw; # Resistance of armature circuit\n",
+ "Ea=VT+Ia*Racir; # Induced emf\n",
+ "# Display result on command window\n",
+ "print\"Induced emf =\",Ea,\"V\""
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "metadata": {},
+ "source": [
+ "## Example E07 : Pg 418"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": 7,
+ "metadata": {
+ "collapsed": false
+ },
+ "outputs": [
+ {
+ "name": "stdout",
+ "output_type": "stream",
+ "text": [
+ "Induced emf = 460.029864137 V\n"
+ ]
+ }
+ ],
+ "source": [
+ "# Example 10.7\n",
+ "# Computation of cemf\n",
+ "# Page No. 418\n",
+ "# Given data\n",
+ "Rf=408.5; # Field resistance \n",
+ "VT=500.; # Rated voltade of the machine\n",
+ "IT=51.0; # Total current\n",
+ "Ra=0.602; # Armature resistance\n",
+ "Ripcw=0.201; # Resistance of interpolar winding and compensating windings\n",
+ "\n",
+ "# Induced emf\n",
+ "If=VT/Rf; # Current\n",
+ "Ia=IT-If; # Armature current\n",
+ "Racir=Ra+Ripcw; # Resistance of armature circuit\n",
+ "Ea=VT-Ia*Racir; \n",
+ "\n",
+ "\n",
+ "# Display result on command window\n",
+ "print\"Induced emf =\",Ea,\"V\""
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "metadata": {},
+ "source": [
+ "## Example E08 : Pg 420"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": 8,
+ "metadata": {
+ "collapsed": false
+ },
+ "outputs": [
+ {
+ "name": "stdout",
+ "output_type": "stream",
+ "text": [
+ "New armature current = 32.0453177866 A\n"
+ ]
+ }
+ ],
+ "source": [
+ "# Example 10.8\n",
+ "# Computation of new armature current\n",
+ "# Page No. 420\n",
+ "# Given data\n",
+ "Rf=120.; # Resistance of inserted resistor\n",
+ "VT=240.; # Rated voltade of the machine\n",
+ "IT=91.; # Total current\n",
+ "Racir=0.221; # Armature sircuit resistance\n",
+ "n2=634.; # New speed after resistor was inserted\n",
+ "n1=850.; # Rated speed OF THE MACHINE\n",
+ "Rx=2.14; # Resistance inserted in series witH armature\n",
+ "\n",
+ "# New armature current\n",
+ "\n",
+ "If=VT/Rf; # Resistor current\n",
+ "Ia1=IT-If; # Armature current\n",
+ "Ia2=(VT-(n2/n1)*(VT-Ia1*Racir))/(Racir+Rx);\n",
+ "\n",
+ "\n",
+ "# Display result on command window\n",
+ "print\"New armature current =\",Ia2,\"A\""
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "metadata": {},
+ "source": [
+ "## Example E09 : Pg 421"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": 9,
+ "metadata": {
+ "collapsed": false
+ },
+ "outputs": [
+ {
+ "name": "stdout",
+ "output_type": "stream",
+ "text": [
+ "Steady state armature current = 24.0 A\n",
+ "Steady state speed = 3045.70319393 r/min\n"
+ ]
+ }
+ ],
+ "source": [
+ "# Example 10.9\n",
+ "# Computation of (a) Steady state armature current if a rheostat in the \n",
+ "# shunt field circuit reduces flux in air gap to 75% of its rated value \n",
+ "# (b) Steady state speed for the conditions in (a)\n",
+ "# Page No. 421\n",
+ "# Given data\n",
+ "Rf=160.; # Field resistance\n",
+ "VT=240.; # Rated voltade of the machine\n",
+ "IT=37.5; # Total current\n",
+ "Ra=0.213; # Armature resistance\n",
+ "Rip=0.092; # Resistance of interpolar winding\n",
+ "Rcw=0.065; # Resistance of compensating windings\n",
+ "n1=2500.; # Rated speed of the machine\n",
+ "\n",
+ "\n",
+ "# (a) At rated conditions\n",
+ "\n",
+ "If=VT/Rf; # Field current\n",
+ "Ia1=IT-If; # Armature current\n",
+ "Ia2=Ia1*0.50*1./0.75;\n",
+ "\n",
+ "# (b) steady state speed for the above mentioned conditions\n",
+ "\n",
+ "Racir=Ra+Rip+Rcw;\n",
+ "\n",
+ "n2=n1*(VT-(Ia2*(1.+Racir)))/0.75*(1./(VT-(Ia1*Racir)));\n",
+ "\n",
+ "\n",
+ "# Display result on command window\n",
+ "\n",
+ "print\"Steady state armature current =\",Ia2,\"A\"\n",
+ "print\"Steady state speed =\",n2,\"r/min\""
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "metadata": {},
+ "source": [
+ "## Example E10 : Pg 427"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": 10,
+ "metadata": {
+ "collapsed": false
+ },
+ "outputs": [
+ {
+ "name": "stdout",
+ "output_type": "stream",
+ "text": [
+ "Mechanical power developed= 31345.5180615 %0.0f W 31345.5180615\n",
+ "Mechanical power developed= 42.0181207258 hp 42.0181207258\n",
+ "Torque developed = 88.2689788611 lb-ft \n",
+ "Shaft torque = 84.032 lb-ft \n"
+ ]
+ }
+ ],
+ "source": [
+ "# Example 10.10\n",
+ "# Computation of (a) Mechanical power developed (b) Torque developed \n",
+ "# (c) Shaft torque\n",
+ "# Page No.427\n",
+ "# Given data\n",
+ "T=40.; # Hp rating of motor\n",
+ "Rf=95.3; # Field resistance\n",
+ "VT=240.; # Rated voltade of the machine\n",
+ "IT=140.; # Total current\n",
+ "Racir=0.0873; # Armature circuit resistance\n",
+ "n=2500.; # Rated speed of the machine\n",
+ "\n",
+ "\n",
+ "# (a) The mechanical power developed\n",
+ "\n",
+ "If=VT/Rf; # Field winding current\n",
+ "Ia1=IT-If; # Armature current\n",
+ "Ea=VT-Ia1*Racir; # Armature emf\n",
+ "Pmech=Ea*Ia1; # Mechanical power\n",
+ "Pmechhp=Ea*Ia1/746.;\n",
+ "\n",
+ "# (b) Torque developed\n",
+ "\n",
+ "TD=7.04*Ea*Ia1/n;\n",
+ "\n",
+ "# (c) Shaft torque\n",
+ "\n",
+ "Tshaft=T*5252./n;\n",
+ "\n",
+ "# Display result on command window\n",
+ "print\"Mechanical power developed=\",Pmech,\"%0.0f W \",Pmech\n",
+ "print\"Mechanical power developed=\",Pmechhp,\"hp \",Pmechhp\n",
+ "print\"Torque developed =\",TD,\"lb-ft \"\n",
+ "print\"Shaft torque =\",Tshaft,\"lb-ft \""
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "metadata": {},
+ "source": [
+ "## Example E11 : Pg 430"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": 11,
+ "metadata": {
+ "collapsed": false
+ },
+ "outputs": [
+ {
+ "name": "stdout",
+ "output_type": "stream",
+ "text": [
+ "Electrical losses = 4755.35625 W\n",
+ "Rotational losses = 3540.64375 W\n",
+ "Efficiency = 91.7698412698 Percent\n"
+ ]
+ }
+ ],
+ "source": [
+ "# Example 10.11\n",
+ "# Determine (a) Electrical losses (b) Rotational losses (c) Efficiency\n",
+ "# Page No. 430\n",
+ "# Given data\n",
+ "T=124.; # Hp rating of motor\n",
+ "Rf=32.0; # Field resistance\n",
+ "VT=240.; # Rated voltade of the machine\n",
+ "IT=420.; # Total current\n",
+ "Ra=0.00872; # Armature resistance\n",
+ "RipRcw=0.0038; # Resistance of interpolar winding and compensating windings\n",
+ "Pout=92504.;\n",
+ "Vb=2.0; # Rated speed of the machine\n",
+ "Racir=Ra+RipRcw;\n",
+ "\n",
+ "# (a) Electrical losses \n",
+ "\n",
+ "If=VT/Rf; # Field current\n",
+ "Ia=IT-If; # Armature current\n",
+ "Pf=If**2.*Rf; # Field power\n",
+ "Paipcw=Ia**2.*(Ra+RipRcw);\n",
+ "Pb=Vb*Ia; # Brush loss power\n",
+ "Plosses=Pf+Paipcw+Pb; # Total power loss\n",
+ "\n",
+ "# (b) Rotational losses\n",
+ "\n",
+ "Ea=VT-(Ia*Racir)-Vb; # Armature emf \n",
+ "Pmech=Ea*Ia; # Mechanical power\n",
+ "Pshaft=T*746.; # Shaft power \n",
+ "Protational=Pmech-Pshaft;\n",
+ "\n",
+ "# (c) Ffficiency\n",
+ "\n",
+ "eeta=Pout/(VT*IT)*100.;\n",
+ "\n",
+ "# Display result on command window\n",
+ "\n",
+ "print\"Electrical losses =\",Plosses,\"W\"\n",
+ "print\"Rotational losses =\",Protational,\"W\"\n",
+ "print\"Efficiency =\",eeta,\"Percent\""
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "metadata": {},
+ "source": [
+ "## Example E12 : Pg 433"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": 12,
+ "metadata": {
+ "collapsed": false
+ },
+ "outputs": [
+ {
+ "name": "stdout",
+ "output_type": "stream",
+ "text": [
+ "Rated torque = 45.0171428571 lb-ft \n",
+ "Armature current = 821.428571429 A\n",
+ "Armature current for 200 percent rated torque = 109.042335766 %0.1f A \n",
+ "External resistance required = 1.82927249846 %0.2f Ohm \n",
+ "Locked rotor torque = 78.6736267891 lb-ft \n"
+ ]
+ }
+ ],
+ "source": [
+ "# Example 10.12\n",
+ "# Determine (a) Rated torque (b) Armature current at locked rotor if no\n",
+ "# starting resistance is used (c) External resistance required in the armature\n",
+ "# circuit that would limit the current and develop 200 percent rated torque\n",
+ "# when starting (d) Assuming the system voltage drops to 215V, determine the \n",
+ "# locked rotor torque using the external resistor in (c)\n",
+ "# Page No. 433\n",
+ "# Given data\n",
+ "n=1750.; # Rotor speed\n",
+ "P=15.; # Hp rating of motor\n",
+ "VT=230.; # Rated voltade of the machine\n",
+ "Ea=0;\n",
+ "Racir=0.280; # Armature circuit loss\n",
+ "Rf=137.; # Field resistance\n",
+ "ItRated=56.2; # Total current drawn\n",
+ "VT1=215.; # Rated voltage after drop\n",
+ "\n",
+ "# (a) Rated torque\n",
+ "Trated=P*5252./n;\n",
+ "\n",
+ "# (b) Armature current\n",
+ "Ia=(VT-Ea)/Racir; \n",
+ "\n",
+ "# (c) External resistance required\n",
+ "If=VT/Rf; # Field current\n",
+ "IaRated=ItRated-If; # Rated armature current\n",
+ "\n",
+ "Ia2=IaRated*2.; # Armature current for 200% rated torque\n",
+ "\n",
+ "Rx=((VT-Ea)/Ia2)-Racir; # External resistance required\n",
+ "\n",
+ "# (d) Locked rotor torque \n",
+ "If215=VT1/Rf; # Field current at 215V\n",
+ "Ia215=(VT1-Ea)/(Racir+Rx); # Armature current at 215V\n",
+ "TD2=Trated*( (If215*Ia215) / (If*IaRated) );\n",
+ "\n",
+ "# Display result on command window\n",
+ "\n",
+ "print\"Rated torque =\",Trated,\"lb-ft \"\n",
+ "print\"Armature current =\",Ia,\"A\"\n",
+ "print\"Armature current for 200 percent rated torque =\",Ia2,\" %0.1f A \"\n",
+ "print\"External resistance required =\",Rx,\" %0.2f Ohm \"\n",
+ "print\"Locked rotor torque =\",TD2,\"lb-ft \""
+ ]
+ }
+ ],
+ "metadata": {
+ "anaconda-cloud": {},
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+ "display_name": "Python [Root]",
+ "language": "python",
+ "name": "Python [Root]"
+ },
+ "language_info": {
+ "codemirror_mode": {
+ "name": "ipython",
+ "version": 2
+ },
+ "file_extension": ".py",
+ "mimetype": "text/x-python",
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+ "pygments_lexer": "ipython2",
+ "version": "2.7.12"
+ }
+ },
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generated by cgit (git 2.34.1) at 2025-01-24 08:52:23 +0000