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Me593 Sheet 4

The document outlines problems related to electromechanical systems and microprocessors, specifically focusing on DC motor operations under various conditions such as regenerative braking, dynamic braking, and plugging. It includes calculations for internal voltage, braking current, resistance, braking torque, and conditions for maintaining speed against overhauling loads. The problems are designed for students in the Mechanical Engineering Department to apply theoretical knowledge to practical scenarios.

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Omar Mostafa
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51 views2 pages

Me593 Sheet 4

The document outlines problems related to electromechanical systems and microprocessors, specifically focusing on DC motor operations under various conditions such as regenerative braking, dynamic braking, and plugging. It includes calculations for internal voltage, braking current, resistance, braking torque, and conditions for maintaining speed against overhauling loads. The problems are designed for students in the Mechanical Engineering Department to apply theoretical knowledge to practical scenarios.

Uploaded by

Omar Mostafa
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as PDF, TXT or read online on Scribd
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COLLEGE OF ENGINEERING & TECHNOLOGY

Department: Mechanical Engineering Department, Smart-Village Campus

Course: Electromechanical systems & microprocessors

Course Code: ME 593


Lecturer: Dr. Mohamed Abdelaziem

Sheet 4
1. A 220 V, 200 A, 800 rpm DC separately excited motor has an armature resistance of
0.05 Ohm. The motor armature is fed from a variable voltage source with an internal
resistance of 0.04 Ohm. Calculate internal voltage of the variable voltage source when
the motor is operating in regenerative braking at 80% at the rated motor torque and
speed of 600 rpm.

2. A 220 V DC series motor runs at 1000 rpm and consumes an armature current of
100 A when driving a load. Resistances of the armature and field windings are 0.05
ohm each. It is operated under dynamic braking at twice the rated torque and 800 rpm
speed. Calculate the value of braking current and resistance.

3. A 220 V, 970 rpm, 100 A DC separately excited motor has an armature resistance of
0.05 ohm. It is braked by plugging from an initial speed of 1000 rpm. Calculate:
• The Resistance to be placed in armature circuit to limit braking current to twice the
full load value.
• The braking torque.
• The torque when the speed has fallen to zero.

4. A magnetization characteristics of a DC series motor when running at 500 rpm is


given by:

The total resistance of the armature and field windings is 0.5 ohm. When connected
for dynamic braking against an overhauling load of 500 N.m, the motor speed is to be
maintained at 600 rpm. What resistance must be connected across the motor
terminals?

1
5. A DC shunt motor has an armature resistance of 0.04 ohm and the field winding
resistance of 10 ohm. The motor is coupled to an overhauling load with a torque of
400 N.m. The following magnetization curve was measured at 600 rpm:

a) The motor is braked by self-excited dynamic braking with a braking resistance of 1


ohm. At what speed the motor will hold the load?
b) Calculate the value of the braking resistance when the motor is required to hold an
overhauling load at 1200 rpm.

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