{
"metadata": {
"name": "",
"signature": "sha256:6b51ae63262d051d8c33b477f21b4f8b38c9632d3bf6e663f7b45ca75bc3f387"
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"worksheets": [
{
"cells": [
{
"cell_type": "heading",
"level": 1,
"metadata": {},
"source": [
"Chapter 8: DC Motors"
]
},
{
"cell_type": "heading",
"level": 3,
"metadata": {},
"source": [
"Example 8.1: page 137:"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"from __future__ import division\n",
"import math\n",
"\n",
"#given data :\n",
"s=22;# shaft of the motor in hp\n",
"Tsh=210;# torue in hp\n",
"\n",
"#calculations:\n",
"N=(s*60*746)/(2*math.pi*Tsh);\n",
"\n",
"#Results\n",
"print \"speed,N(rpm) = \",N "
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"speed,N(rpm) = 746.300264578\n"
]
}
],
"prompt_number": 1
},
{
"cell_type": "heading",
"level": 3,
"metadata": {},
"source": [
"Example 8.2: Page 143:"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"\n",
"from __future__ import division\n",
"import math\n",
"\n",
"#given data :\n",
"N=955;# in r.p.m\n",
"V=230;# voltage in volts\n",
"I=72;# current in A\n",
"s=968;# stray losses\n",
"Rsh=115;# shunt field resistance in ohm\n",
"Ra=0.5# armature resistance in ohm\n",
"\n",
"#calculations:\n",
"W=V*I;\n",
"Ish=V/Rsh# shunt field resistance\n",
"Ia=I-Ish;\n",
"Eb=V-(Ia*Ra)# back emf in volts\n",
"Dpd=Eb*Ia# driving power developed\n",
"Mpo=Dpd-s;\n",
"bhp=Mpo/746;\n",
"c_losses=W-Dpd;\n",
"Ta=(9.55*Eb*Ia)/N;\n",
"Tsh=(bhp*60*746)/(2*math.pi*N);\n",
"Tl=Ta-Tsh;\n",
"eta=(Mpo/W)*100;\n",
"\n",
"#Results\n",
"print \"(a)bhp = \",bhp\n",
"print \"(b)copper losses(W) = \",c_losses\n",
"print \"(c)torque armature,Ta(N-m) = \",Ta\n",
"print \"(d)shaft torque,Tsh(N-m) = \",round(Tsh,2)\n",
"print \"(e)lost torque,Tl(N-m) = \",round(Tl,2)\n",
"print \"(f)commercial efficioency,eta(%) = \",round(eta,2)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"(a)bhp = 17.0\n",
"(b)copper losses(W) = 2910.0\n",
"(c)torque armature,Ta(N-m) = 136.5\n",
"(d)shaft torque,Tsh(N-m) = 126.81\n",
"(e)lost torque,Tl(N-m) = 9.69\n",
"(f)commercial efficioency,eta(%) = 76.58\n"
]
}
],
"prompt_number": 2
},
{
"cell_type": "heading",
"level": 3,
"metadata": {},
"source": [
"Example 8.3: page 144:"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"\n",
"from __future__ import division\n",
"import math\n",
"\n",
"#given data:\n",
"V=230# in volts\n",
"I=5 # in amperes\n",
"rpm=914#turns\n",
"ra=0.5#resistance of armature in ihms\n",
"rsh=115#shunt field in ohms\n",
"Il=30# in amperes\n",
"ar=10# in percent\n",
"\n",
"#calculations:\n",
"Ish=V/rsh# in amperes\n",
"anl=I-Ish#armature current in amperes at no load\n",
"al=Il-Ish#armature currentin amperes at load\n",
"Eb1=(V-anl*ra)#back emf at no load\n",
"Eb2=(V-al*ra)#back emf at load\n",
"ph1=100#\n",
"ph2=90#\n",
"Ns=(rpm*Eb2*ph1)/(Eb1*ph2)#speed when loaded in rpm\n",
"\n",
"#Results\n",
"print \"speed when loaded in rpm is \",Ns"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"speed when loaded in rpm is 960.0\n"
]
}
],
"prompt_number": 3
},
{
"cell_type": "heading",
"level": 3,
"metadata": {},
"source": [
"Example 8.4: page 144:"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"\n",
"from __future__ import division\n",
"import math\n",
"\n",
"#given data:\n",
"Il=83# WHEN LOADED IN AMPERES\n",
"V=110# in volts\n",
"I=5 # in amperes without load\n",
"ra=0.5#armature resistance in ohms\n",
"rsh=110#shunt field in ohms\n",
"\n",
"#calculations:\n",
"Ish=V/rsh# in ampere\n",
"anl=I-Ish#armature current in amperes at no load\n",
"al=Il-Ish#armature currentin amperes at load\n",
"Eb1=(V-anl*ra)#back emf at no load\n",
"Eb2=(V-al*ra)#back emf at load\n",
"Dp=Eb1*anl#driving power at no load in watt\n",
"Dpl=Eb2*al#driving power at load in watt\n",
"mo=Dpl-Dp#out of motor in watt\n",
"bhp=mo/746#horse power\n",
"mi=V*Il#input power in watt\n",
"n=(mo/mi)*100#efficiency in percentage\n",
"\n",
"#Results\n",
"print \"(a)stray losses in watt is\",Dp\n",
"print \"(b)horse power in ampere is\",round(bhp,1)\n",
"print \"(c)efficiency of motor when it is work on full ,load in percentage is\",round(n,2)\n",
"#answer(c) is wrong in the textbook"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"(a)stray losses in watt is 432.0\n",
"(b)horse power in ampere is 7.0\n",
"(c)efficiency of motor when it is work on full ,load in percentage is 57.24\n"
]
}
],
"prompt_number": 4
},
{
"cell_type": "heading",
"level": 3,
"metadata": {},
"source": [
"Example 8.5: page 146"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"\n",
"from __future__ import division\n",
"import math\n",
"\n",
"#given data:\n",
"V=230# in volts\n",
"I=60# in amperes\n",
"rpm=955#turns\n",
"ra=0.2#resistance of armature in ihms\n",
"rsh=0.15#shunt field in ohms\n",
"sl=604#stray losses in watts\n",
"\n",
"#calculations:\n",
"Rm=ra+rsh# in ohms\n",
"Eb=(V-I*Rm)# back emf in volts\n",
"Dp=Eb*I#driving power in watts\n",
"mi=V*I#input power in watts\n",
"Cl=mi-Dp# copper losses in watts\n",
"mo=Dp-sl#output of motor\n",
"bhp=mo/746# horse power in bhp\n",
"Ta=(9.55*Eb*I)/rpm#total torque in N-m\n",
"Ts=(bhp*60*746)/(2*math.pi*rpm)#shaft torque in N-m\n",
"Tl=Ta-Ts#lost torque in N-m\n",
"nc=(mo/mi)*100#commercial efficiency in percentge\n",
"\n",
"#Results\n",
"print \"(a)back emf in volts is\",Eb\n",
"print \"(b)copper losses in watts is \",Cl\n",
"print \"(c)horse power is\", bhp\n",
"print \"(d)total torque in N-m is\",Ta\n",
"print \"(e)shaft torque in N-m is\",round(Ts,1)\n",
"print \"(f)lost torque in N-m is\",round(Tl,1)\n",
"print \"(g)commercial efficiency in percentge is\",round(nc,2)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"(a)back emf in volts is 209.0\n",
"(b)copper losses in watts is 1260.0\n",
"(c)horse power is 16.0\n",
"(d)total torque in N-m is 125.4\n",
"(e)shaft torque in N-m is 119.4\n",
"(f)lost torque in N-m is 6.0\n",
"(g)commercial efficiency in percentge is 86.49\n"
]
}
],
"prompt_number": 5
},
{
"cell_type": "heading",
"level": 3,
"metadata": {},
"source": [
"Example 8.6: page 146:"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"\n",
"from __future__ import division\n",
"import math\n",
"\n",
"#given data:\n",
"V=220# in volts\n",
"I=60# in amperes\n",
"rpm=728#turns\n",
"Ts=150#shaft torque in N-m\n",
"nc=80#commercial efficiency in percentge\n",
"\n",
"#calculations:\n",
"I=((Ts*2*math.pi*rpm*746)/(60*746*(nc/100)*V))# CURRENT TAKEN IN AMPERES\n",
"\n",
"#Results\n",
"print \"current taken in amperes is\",round(I,1) "
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"current taken in amperes is 65.0\n"
]
}
],
"prompt_number": 6
},
{
"cell_type": "heading",
"level": 3,
"metadata": {},
"source": [
"Example 8.7: page 147:"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"\n",
"from __future__ import division\n",
"import math\n",
"\n",
"#given data:\n",
"V=220# in volts\n",
"rpm=2100#turns\n",
"ra=0.5#resistance of armature in ihms\n",
"rsh=220#shunt field in ohms\n",
"Il=21# in amperes\n",
"R1=220# in ohms\n",
"ph1=50#\n",
"ph2=100#\n",
"\n",
"#calculations:\n",
"Ish=V/rsh# in amperes\n",
"Ifs=V/(rsh+R1)#shunt field current in second case in ampere\n",
"n2=(rpm*ph2)/ph1#speed in rpm\n",
"\n",
"#Results\n",
"print \"speed in rpm is\",n2"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"speed in rpm is 4200.0\n"
]
}
],
"prompt_number": 7
}
],
"metadata": {}
}
]
}