focus on DC motors. You will need to submit all MATLAB work with your exam,

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ECEP352-Motor Control Principles-Exam 3-Due March 15, 2018

In this exam, you will focus on DC motors. You will need to submit all MATLAB work with your exam, as we will run software to detect any cheating. This is an exam, so you are not to give or receive help from any source other than your textbook.

I have neither given nor received aid on this examination, and understand any violation of Drexel University’s academic honesty policy will be handled

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Base Motor Information

Motor 1

This motor is a shunt DC motor (with compensation windings) with the following informa- tion:

Parameter Variable Value Units Terminal Voltage VT 400 V

Armature Resistance RA 0.1 A Field Resistance RF 50 A Reference Speed n0 1800 RPM

Load Current IL 10-300 A

Motor 2

This motor is a shunt DC motor (without compensation windings) with the following infor- mation:

Parameter Variable Value Units Terminal Voltage VT 400 V

Armature Resistance RA 0.1 A Field Resistance RF 50 A Reference Speed n0 1800 RPM

Load Current IL 10-300 A Number of Turns on Field Winding NF 2200 turns

Reference Armature MMF FAR0 1200 A· turns Load Current at FAR0 IL0 100 A

The magnetization curve for this motor is supplied in the MATLAB file magcurve1. The two variables in this file are called if values and ea values, representing the field current and open-circuit terminal voltage.

Motor 3

This motor is a series DC motor with the following information:

Parameter Variable Value Units Terminal Voltage VT 400 V

Armature+Field Resistance RAF 0.1 A Number of Turns on Field Winding NF 30 A

Reference Speed n0 1800 RPM Load Current IL 200-300 A

The magnetization curve for this motor is supplied in the MATLAB file magcurve2. The two variables in this file are called mmf values and ea values, representing the magnetomotive force and internal generated voltage.

Motor 4

This motor is a compounded DC motor with the following information:

Parameter Variable Value Units Terminal Voltage VT 400 V

Armature+Field Resistance RAF 0.02 A Number of Turns on Shunt Winding Nshunt 1100 turns Number of Turns on Series Winging Nseries 3 turns

Reference Speed n0 1800 RPM Armature Current IA 10-300 A

Problem 1-30 Points

For this problem, you are to provide the torque-speed curve of each motor on the same plot. The armature current values for each motor are stated in the motor information section. These currents should be incremented by 1 A to created the torque-speed curves. Addition- ally, the compounded DC motor should have two curves, one cumulative compounded and one differential compounded.

For the shunt DC motor without compensation case, assume the magnetomotive force (MMF) scales linearly with the field current.

The plot should have the following annotations:

� Proper labeling of axes

� Title

� Legend

� Grid

Problem 2-25 Points

Plot the efficiency vs motor speed for each motor, in percent, on one plot. Provide proper labeling and legend. Explain the reasoning for each motor’s efficiency behavior.

Problem 3-30 Points

In this problem, you will be working with the shunt DC motor with compensating windings (motor 1), specifically with speed control.

Problem 3a-Changing Field Resistance

Motor 1 was taken apart for maintenance. During the examination, the following facts were found:

� Plex of windings: 2 (lap wound)

� Number of poles: 6

� Number of coils on armature: 72

� Number of turns per coil: 12

For this problem, you are to change the field resistance to 55 Ω. Plot the torque-speed curve for the original motor and the modified motor on the same plot.

Problem 3b-Changing Armature Resistance

The original motor now has its armature resistance changed to 0.5 Ω. Plot the torque-speed curve for the original motor and the modified motor on the same plot.

For all plots in Problem 3, place the original torque-speed curve for motor 1 and the modified motor torque-speed curve on the same plots. Provide a detailed explanation to the behavior of the plots.

Problem 4-15 Points

In part of Problem 3, you analyzed the torque-speed curves of the original motor 1 and motor 1 with a new field resistor. The plots should intersect at a point. Consider the case where a designer wants to have that intersection be at a certain point on the torque-speed curve. Show (aka derive) the intersection point of the lines created by the two lines is

τind = ( VTK

RA )( RF1 RF2

)φ1 (1)

nm = 30

π ( VT Kφ1

)( R2

R1 + R2 ) (2)

where VT =input voltage (V) K=motor constant RA=armature resistance (Ω) RF1=original field resistance (Ω) RF2=new field resistance (Ω) φ1=original motor flux (Wb)