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{
"metadata": {
"name": ""
},
"nbformat": 3,
"nbformat_minor": 0,
"worksheets": [
{
"cells": [
{
"cell_type": "heading",
"level": 1,
"metadata": {},
"source": [
"CHAPTER 6: CONTROL AND STARTING OF A DC MOTOR"
]
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 6.1, Page number 212"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"#Variable declaration\n",
"V_t = 220.0 #Supply voltage(V)\n",
"I_a1 = 10.0 #Armature current(A)\n",
"N_1 = 900.0 #Speed(rpm)\n",
"R_a = 1.0 #Armature resistance(ohm)\n",
"N_2 = 500.0 #Reduced speed(rpm)\n",
"\n",
"#Calculation\n",
"E_b1 = V_t-I_a1*R_a #Initial back emf(V)\n",
"R = E_b1/I_a1*(1-(N_2/N_1)) #Value of additional resistance(ohm)\n",
"\n",
"#Result\n",
"print('Value of additional resistance , R = %.1f ohm' %R)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Value of additional resistance , R = 9.3 ohm\n"
]
}
],
"prompt_number": 1
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 6.2, Page number 212-213"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"#Variable declaration\n",
"V_t = 230.0 #Supply voltage(V)\n",
"I_a1 = 15.0 #Armature current(A)\n",
"N_1 = 650.0 #Speed(rpm)\n",
"R_a = 0.4 #Armature resistance(ohm)\n",
"R = 1.0 #Variable resistance in series with the armature(ohm)\n",
"\n",
"#Calculation \n",
"E_b1 = V_t-I_a1*R_a #Initial back emf(V)\n",
"#At full load torque\n",
"E_b2 = V_t-I_a1*(R+R_a) #Final back emf(V)\n",
"N_2 = N_1*(E_b2/E_b1) #Speed at full load torque(rpm)\n",
"\n",
"#At half load torque\n",
"I_a2hl = I_a1/2 #Armature current(A)\n",
"E_b2hl = V_t-I_a2hl*(R+R_a) #Back emf(V)\n",
"N_2hl = N_1*(E_b2hl/E_b1) #Speed at half load torque(rpm)\n",
"\n",
"#Result\n",
"print('Speed at full load torque , N_2 = %.1f rpm' %N_2)\n",
"print('Speed at half load torque , N_2 = %.1f rpm' %N_2hl)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Speed at full load torque , N_2 = 606.5 rpm\n",
"Speed at half load torque , N_2 = 636.9 rpm\n"
]
}
],
"prompt_number": 1
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 6.3, Page number 215-216"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"#Variable declaration\n",
"V_t = 230.0 #Supply voltage(V)\n",
"R_af = 0.2 #Total resistance of armature & field(ohm)\n",
"I_a1 = 10.0 #Armature current for certain load(A)\n",
"N = 1000.0 #Motor speed for certain load(rpm)\n",
"R_1 = 0 #Variable resistance for certain load(ohm)\n",
"I_a2 = 8.0 #Armature current for other load(A)\n",
"R_2 = 2.0 #Variable resistance for other load(ohm)\n",
"phi_1 = 1.0 #Assuming flux in certain load(Wb)\n",
"phi_2 = 0.8*phi_1 #Flux in other load(Wb)\n",
"\n",
"#Calculation\n",
"#For certain load\n",
"R_a1 = R_af+R_1 #New armature resistance(ohm)\n",
"E_b1 = V_t-I_a1*R_a1 #Back emf(V)\n",
"#For other load\n",
"R_a2 = R_af+R_2 #New armature resistance(ohm)\n",
"E_b2 = V_t-I_a2*R_a2 #Back emf(V)\n",
"N_2 = (E_b2/E_b1)*(phi_1/phi_2)*N #New speed(rpm) \n",
"\n",
"#Result\n",
"print('New speed , N_2 = %.1f rpm' %N_2)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"New speed , N_2 = 1164.5 rpm\n"
]
}
],
"prompt_number": 1
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 6.4, Page number 216-218"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"#Variable declaration\n",
"N = 1100.0 #Speed of dc series motor(rpm)\n",
"P = 4.0 #Number of poles\n",
"path = 4.0 #Number of parallel paths\n",
"I_a1 = 15.0 #Supply current to dc series motor(A)\n",
"V_t = 220.0 #Supply voltage(V)\n",
"R_a = 0.9 #Series armature resistance(ohm)\n",
"R_se = 0.6 #Series field resistance(ohm)\n",
"I_a2 = 25 #Supply current to dc series motor(A)\n",
"phi_1 = 1.0 #Assuming flux for 15 A case(Wb)\n",
"phi_2 = 0.8*phi_1 #Flux in 25 A case(Wb)\n",
"\n",
"#Calculation\n",
"#First case\n",
"R_se1 = R_se #Total series field resistance(ohm)\n",
"E_b1 = V_t-I_a1*(R_a+R_se1) #Back emf(V)\n",
"#Second case\n",
"R_se2 = R_se1/path #Total series field resistance(ohm)\n",
"E_b2 = V_t-I_a2*(R_a+R_se2) #Back emf(V)\n",
"N_2 = (E_b2/E_b1)*(phi_1/phi_2)*N #New speed(rpm) \n",
"\n",
"#Result\n",
"print('Speed for second case , N_2 = %.1f rpm = %.f rpm' %(N_2,N_2))"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Speed for second case , N_2 = 1348.9 rpm = 1349 rpm\n"
]
}
],
"prompt_number": 1
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 6.5, Page number 233-234"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"#Variable declaration\n",
"V_t = 230.0 #Shunt motor supply voltage(V)\n",
"R_a = 0.4 #Armature resistance(ohm)\n",
"I_a = 30.0 #Armature current(A)\n",
"n = 3.0 #Number of steps\n",
"\n",
"#Calculation\n",
"R_1 = V_t/I_a #Maximum resistance(ohm)\n",
"k = (R_1/R_a)**(1.0/3) #Constant\n",
"R_2 = R_1/k #Resistance(ohm)\n",
"R_3 = R_2/k #Resistance(ohm)\n",
"R_4 = R_3/k #Resistance(ohm)\n",
"R_1step = R_1-R_2 #Resistance of the first step(ohm)\n",
"R_2step = R_2-R_3 #Resistance of the second step(ohm)\n",
"R_3step = R_3-R_4 #Resistance of the third step(ohm)\n",
"\n",
"#Result\n",
"print('Resistance of the first step , R_1step = %.1f ohm' %R_1step)\n",
"print('Resistance of the second step , R_2step = %.1f ohm' %R_2step)\n",
"print('Resistance of the third step , R_3step = %.2f ohm' %R_3step)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Resistance of the first step , R_1step = 4.8 ohm\n",
"Resistance of the second step , R_2step = 1.8 ohm\n",
"Resistance of the third step , R_3step = 0.67 ohm\n"
]
}
],
"prompt_number": 1
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 6.6, Page number 234-236"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"#Variable declaration\n",
"V_t = 220.0 #Shunt motor supply voltage(V)\n",
"P_0 = 3550.0 #Output power(W) \n",
"n = 0.85 #Efficiency\n",
"\n",
"#Calculation\n",
"P_in = P_0/n #Input power(W)\n",
"P_tloss = P_in-P_0 #Total loss(W)\n",
"I_a = P_in/V_t #Armature current(A)\n",
"P_cu = P_tloss/2 #Copper loss(W)\n",
"R_a = P_cu/I_a**2 #Armature resistance(ohm)\n",
"I_1 = 2*I_a #Maximum starting current(A)\n",
"R_1 = V_t/I_1 #Maximum resistance(ohm)\n",
"k = (R_1/R_a)**(1.0/4) #Constant\n",
"R_2 = R_1/k #Resistance(ohm)\n",
"R_3 = R_2/k #Resistance(ohm)\n",
"R_4 = R_3/k #Resistance(ohm)\n",
"R_5 = R_4/k #Resistance(ohm)\n",
"R_1step = R_1-R_2 #Resistance of the first step(ohm)\n",
"R_2step = R_2-R_3 #Resistance of the second step(ohm)\n",
"R_3step = R_3-R_4 #Resistance of the third step(ohm)\n",
"R_4step = R_4-R_5 #Resistance of the fourth step(ohm)\n",
"\n",
"#Result\n",
"print('Resistance of the first step , R_1step = %.1f ohm' %R_1step)\n",
"print('Resistance of the second step , R_2step = %.2f ohm' %R_2step)\n",
"print('Resistance of the third step , R_3step = %.2f ohm' %R_3step)\n",
"print('Resistance of the fourth step , R_4step = %.2f ohm' %R_4step)"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Resistance of the first step , R_1step = 2.2 ohm\n",
"Resistance of the second step , R_2step = 1.36 ohm\n",
"Resistance of the third step , R_3step = 0.85 ohm\n",
"Resistance of the fourth step , R_4step = 0.53 ohm\n"
]
}
],
"prompt_number": 1
}
],
"metadata": {}
}
]
}
|
