Question

QUESTIONS Question-3: Draw "speed vs. torque" curve using data in Table-1. The completed graph represents the speed vs. torque characteristics of a typical DC shunt-wound motor. Terax Question-4: Calculate the speed regulation (full load - 12 lbf.in) using the equation: 2-143) 143 (no load Regulation (full load speed) Speed regulation- % Part-II - Motor Efficiency Calculation: Set the dynamometer control knob at its full CW position (to provide the maximum starting load for the shunt-wound motor). Turn on the power supply and gradually increase the DC voltage until the motor is drawing 3 A of line current. The motor should turn very slowly or not at all. Measure and record the DC voltage and the torque developed. 1. 2. 3. E> 2.2 Torque =-N. V ; Return the voltage to zero and turn off the power supply. POST-LAB: Question-5: Calculate the mechanical output power by the shunt-wound DC motor when the 4. torque is 9 Ibf.in (1.02 Nm). Use the equation: 1.59.N.T Pout (hp)100000 where: Pout-Mechanical Output Power in horse power (hp) N Speed in revolutions per minute (r/min) T -Torque in pound-force-inches (Ibf.in) Pout =- hp Question-6: Calculate the output and input power in watts (1 hp-746 W) for the motor load of 9 lbf.in (in Question-3)? Question-7: Knowing the input and output power in watts, calculate the efficiency of the motor in Question 3. Efficiency = (power out/power in) x 100% Efficiency % Question-8: Calculate the losses (in watts of the motor in Question 3)? Question-9: List all sources heat losses in a DC machine. Question-10: Would the motor load increase if a cooling fan is mounted on the motor shaft (Yes or No)? Explain. Question-11: Give two reasons why losses are undesirable. Question-12: We are often asked "How much torque does this motor have"? Strictly speaking. this question is not complete. Knowing the theory of electrical motors, how do you "reframe" this question to make it more complete or strictly correct? Recommendation for improvement: Provide at least one recommendation to improve experiment. Note that anything which was unusual to you might be an opportunity for improvement. (3 points out of 30 points)

Answer 1

Question 9: Sources of Heat:

Heat generate due to ohmic energy losses in the winding. Winding is made up of wire and have resistance to it. so when current is passed, I²R power is being dissipated as heat.

In DC motor there is shunt field winding, Amrature Windings, Iron losses ( that are being classified as Hysteresis Loss and Eddy current losses) and fiction in ball bearing are the sources of Heat.

Question 10: YES, When a cooling fan is mounted on the shaft it increases the load of the motor because the fan drag the air to the motor, this air resistance and the weight of fan adds to the load of the motor.

Question 11:  Losses are undesirable because:

1) They waste power, can cause excessive heating in the motor, can accelerate wear-out and cause premature failure of the motor, etc.

2) the problems above increase the need for maintenance, thus increasing lifetime cost.

Question 12: How much torque does this motor have?

Torque is not only the main characteristic for the motor to know. a person should also know the Efficiency and power consumption. so the question should be reframed as: What is the efficiency and power consumption of this motor. This would give major idea of power calculation. Please post Full previous questions to able to answer the questions and Recommendation exactly.