Determination of Efficiency and Performance Characteristics of D.C. Shunt Motor
Trade: Electrician | Semester: II
Question: Determine the efficiency of a D.C. shunt motor and plot its performance characteristics.
Introduction
A D.C. shunt motor is widely used due to its constant speed characteristics. Determining its efficiency and performance characteristics is essential to evaluate its performance under different load conditions.
Objective
To determine the efficiency of a D.C. shunt motor and plot its performance characteristics such as speed, torque, and current.
Apparatus Required
- D.C. Shunt Motor
- Voltmeter
- Ammeter
- Wattmeter
- Rheostat
- Load (Brake drum / Dynamometer)
- Tachometer
Theory
In a D.C. shunt motor, the field winding is connected in parallel with the armature. The speed remains nearly constant with load variation. Efficiency is defined as the ratio of output power to input power.
Formula
Efficiency (η) = Output Power / Input Power × 100
Input Power = V × I
Output Power = Torque × Speed
Procedure
- Make proper connections as per circuit diagram.
- Start the motor using a starter.
- Note no-load readings.
- Apply load gradually.
- Record voltage, current, speed, and load.
- Repeat for different load conditions.
Observation Table
| Load | Voltage (V) | Current (A) | Speed (RPM) | Efficiency (%) |
|---|---|---|---|---|
| 1 |
Performance Characteristics
- Speed vs Load
- Current vs Load
- Efficiency vs Load
Graphs
Plot graphs between load and speed, load and current, and load and efficiency.
Precautions
- Check connections properly
- Do not overload motor
- Start motor with starter
Result
The efficiency of the D.C. shunt motor was determined and performance characteristics were plotted.
Conclusion
The D.C. shunt motor shows nearly constant speed with varying load and good efficiency.