× Home MCQ Engineering Calculators Videos Basic Electrical Circuit Theories Electrical Laws Materials Batteries Illumination Generation Transmission Distribution Switchgear Protection Measurement Control System Utilities Safety Transformer Motor Generator Electrical Drives Electronics Devices Power Electronics Digital Electronics Biomedical Instrumentation

Swinburne Test of DC Machine

on 24/2/2012 & Updated on 2/8/2018
This method is an indirect method of testing a DC machine. It is named after Sir James Swinburne. Swinburne's test is the most commonly used and simplest method of testing of shunt and compound wound DC machines which have constant flux. In this test the efficiency of the machine at any load is pre-determined. We can run the machine as a motor or as a generator. In this method of testing no load losses are measured separately and eventually we can determine the efficiency.
The circuit connection for Swinburne's test is shown in figure below. The speed of the machine is adjusted to the rated speed with the help of the shunt regulator R as shown in figure. Connection Diagram of Swinburne's Test

Calculation of Efficiency

Let, I0 is the no load current (it can be measured by ammeter A1) Ish is the shunt field current (it can be measured by ammeter A2)

Related pages
Swinburne Test of DC Machine

Then, no load armature current = Also let, V is the supply voltage. Therefore, No load power input = VI0 watts. In Swinburne's test no load power input is only required to supply the losses. The losses occur in the machine mainly are:

Since the no load mechanical output of the machine is zero in Swinburne's test, the no load input power is only used to supply the losses. The value of armature copper loss = Here, Ra is the armature resistance. Now, no to get the constant losses we have to subtract the armature copper loss from the no load power input.

Then, After calculating the no load constant losses now we can determine the efficiency at any load. Let, I is the load current at which we have to calculate the efficiency of the machine. Then, armature current (Ia) will be (I - Ish), when the machine is motoring. And , when the machine is generating.

Calculation of Efficiency When the Machine is Motoring on Load

Power input = VI Armature copper loss, Constant losses, ∴ Efficiency of the motor:

Calculation of Efficiency When the Machine is Generating on Load

Power input = VI Armature copper loss, Constant losses, ∴ Efficiency of the generator:

Advantages of Swinburne's Test

The main advantages of this test are:
  1. This test is very convenient and economical as it is required very less power from supply to perform the test.
  2. Since constant losses are known, efficiency of Swinburne's test can be pre-determined at any load.
  3. Disadvantages of Swinburne's Test

    The main disadvantages of this test are :
    1. Iron loss is neglected though there is change in iron loss from no load to full load due to armature reaction.
    2. We cannot be sure about the satisfactory commutation on loaded condition because the test is done on no-load.
    3. We can’t measure the temperature rise when the machine is loaded. Power losses can vary with the temperature.
    4. In DC series motors, the Swinburne’s test cannot be done to find its efficiency as it is a no load test.

Please Rate this Article
5
⚑ 1 total
5
4
3
2
1


New Articles
Articles on Testing of DC Motor
Testing of DC MachineSwinburne Test of DC Machine
More Articles on Electric Motor
Basic MotorDC Motor BasicSpeed Control of DC MotorCommutation of DC MotorDC Motor TypesBasic Induction MotorThree Phase Induction MotorStarting of DC MotorSynchronous Motor
Articles Categories
Home
Basic Electrical
Electric Transformer
Electric Generator
Electric Motor
Electrical MCQ
Engineering Calculators
Video Lectures
Electrical Generation
Electric Transmission
Switchgear
Electric Protection
Electrical Measurement
Electronics Devices
Power Electronics
Digital Electronics