Q1. A 120V, dc motor has shunt field windings of 500 turns and field ...
Q1. A 120V, dc motor has shunt field windings of 500 turns and field ...
Q1. A 120V, dc motor has shunt field windings of 500 turns and field ...
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<strong>Q1.</strong> A <strong>120V</strong>, <strong>dc</strong> <strong>motor</strong> <strong>has</strong> <strong>shunt</strong> <strong>field</strong> <strong>windings</strong> <strong>of</strong> <strong>500</strong> <strong>turns</strong> <strong>and</strong> <strong>field</strong> resistance <strong>of</strong> R F = 100 Ω <strong>and</strong><br />
armature resistance <strong>of</strong> R A = 0.10 Ω. The full load current is 40 A, <strong>and</strong> it produces an armature<br />
reaction <strong>of</strong> 100 A-Turns.<br />
140<br />
120<br />
Magnetization Curve at 2400 rpm<br />
2400 rpm<br />
Armature Voltage (V)<br />
100<br />
80<br />
60<br />
40<br />
20<br />
0<br />
0 0.5 1 1.5 2<br />
Field Current (A)<br />
a) Equivalent circuit goes in this box.<br />
(a)(1) Sketch the DC <strong>motor</strong> equivalent circuit in the box above.<br />
Show all components <strong>and</strong> label currents <strong>and</strong> voltages.<br />
(b)(3) What is the full load speed (N FL ) <strong>of</strong> this <strong>motor</strong> in rpm?<br />
(c)(3) What is the full load torque (T) available at the shaft?<br />
(d)(3) What is the <strong>motor</strong> efficiency?<br />
b) N FL = ___________<br />
c) T = ___________<br />
d) % η = ___________
Q2. A permanent magnet DC generator <strong>has</strong> an armature resistance <strong>of</strong> 4.0 ohms <strong>and</strong> operates at<br />
1200 rpm with constant rotational losses <strong>of</strong> 100 W. At no load, a voltage <strong>of</strong> 140V is produced.<br />
(a)(1) Sketch the generator armature circuit. Show all components <strong>and</strong> label currents <strong>and</strong> voltages.<br />
(b)(3) When the machine is operating at an efficiency is 75%, what is the output power produced?<br />
b) P out = _________________<br />
a) Equivalent circuit goes in this box.
Q3. A DC generator is rated at 180 kW, 430 V, 400A <strong>and</strong> 1800 rpm. The armature resistance is<br />
0.04 Ω. The separately excited <strong>field</strong> circuit <strong>has</strong> 1000 <strong>turns</strong> per pole, a resistance <strong>of</strong> 90 Ω <strong>and</strong> is<br />
supplied 450 V. The prime mover <strong>turns</strong> the generator at a constant 1600 rpm. The magnetization<br />
curve (for N = 1800 rpm) is shown below.<br />
(a)(2) Find the no-load terminal voltage .<br />
(b)(3) Find the % voltage regulation assuming a 400A load, <strong>and</strong> no armature reaction?<br />
For parts c <strong>and</strong> d) assume an armature reaction <strong>of</strong> <strong>500</strong> A <strong>turns</strong><br />
(c)(2) Find the terminal voltage for a 400 A load?<br />
(d)(3) At this load, find the <strong>field</strong> current required to boost the terminal voltage to 380 V?<br />
a) V = _____________<br />
b) %VR =__________<br />
c) V = ____________<br />
d) I F = ____________
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