- Trending Categories
- Data Structure
- Networking
- RDBMS
- Operating System
- Java
- iOS
- HTML
- CSS
- Android
- Python
- C Programming
- C++
- C#
- MongoDB
- MySQL
- Javascript
- PHP

- Selected Reading
- UPSC IAS Exams Notes
- Developer's Best Practices
- Questions and Answers
- Effective Resume Writing
- HR Interview Questions
- Computer Glossary
- Who is Who

*Swinburne’s test* is an indirect method of testing DC machines, named after *Sir James Swinburne*. In this method, the losses are determined separately and the efficiency at desired load is predetermined. The Swinburne’s test is the simplest method of testing of shunt and compound DC machines which have constant field flux.

The connection diagram is shown in the figure and the machine is run as a motor at rated voltage and speed.

Let,

$$\mathrm{π = Supply\:voltage}$$

$$\mathrm{πΌ_{0} = No \:load \:line\: current}$$

$$\mathrm{πΌ_{sh} = Shunt\: field \:current}$$

$$\mathrm{\therefore \:No \:load\: armature \:current,\:I_{π0} = I_{0} − I_{sh}}$$

And

$$\mathrm{No load input power = ππΌ_{0}}$$

This no-load input power of the machine supplies the following −

- Core loss
- No-load armature cu loss
- Friction and windage losses

At no-load the useful mechanical output of the machine is zero, thus the no-load input power is only used to supply the losses in the machine. Hence,

$$\mathrm{Armature\:cu − loss\:at\:no − load = (πΌ_{π0})^2π _{π}}$$

Where, R_{a} is the resistance of armature winding.

Therefore, the constant power losses in the machine will be,

$$\mathrm{π_{πΆ} = No\:load \:input\: power − No \:load \:armature \:cu\: loss}$$

$$\mathrm{⇒ π_{πΆ} = ππΌ_{0} − (πΌ_{π0})^2π _{π}}$$

Now, after knowing the constant losses of the machine, its efficiency at any other load can be determined as follows −

Consider "I" is the load current at which the efficiency of the machine is to be calculated.

Here,

$$\mathrm{Armature\:current,\:I_{a} = I − I_{sh}}$$

$$\mathrm{Motor\:input\:power = VI}$$

$$\mathrm{Armature\:Cu\:loss = I_{a}^{2}R_{π} = (I − I_{sh})^2π _{π}}$$

$$\mathrm{\therefore\: Total \:losses\: in\: the\: machine = (I − πΌ_{sh})^2π _{π} + π_{πΆ}}$$

Where, P_{C} is the constant losses which is determined above.

Therefore,

$$\mathrm{Efficiency\:of\:Motor,\: \eta_{π} =\frac{Output}{Input} =\frac{Input − Losses}{Input}}$$

$$\mathrm{⇒ \eta_{π} =\frac{ππΌ − (I − πΌ_{sh})^2π _{π} − π_{πΆ}}{ππΌ}}$$

Here,

$$\mathrm{Armature\:current,\:I_{a} = I + I_{sh}}$$

$$\mathrm{Generator\:output \:power = VI}$$

$$\mathrm{Armature\:Cu\:loss = I_{a}^{2}R_{π} = (I + I_{sh})^2π _{π}}$$

$$\mathrm{\therefore\: Total \:losses\: in\: the\: machine = (I + πΌ_{sh})^2π _{π} + π_{πΆ}}$$

$$\mathrm{Efficiency\: of \:Generator,\: \eta_{π} =\frac{Output}{Output + Losses} =\frac{ππΌ}{ππΌ + (I + πΌ_{sh})^2π _{π} + π_{πΆ}}}$$

Following are the advantages of Swinburne’s test −

- The power required for the testing of large machines is very small, therefore it is an economical and convenient method of testing DC machines.
- As the constant losses are known, thus the efficiency can be pre-determined at any load.

The main disadvantages of the Swinburne’s test are −

- The change in iron losses is not considered from no-load to full load. At full load, due to the armature reaction, the flux is distorted which increases the iron losses.
- Since the Swinburne’s test is performed on no-load, thus it does not indicate whether the commutation on full load is satisfactory and whether the temperature rise would be within specified limits.

The Swinburne’s test has the following limitation −

- The Swinburne’s test is only applicable only to those DC machines in which the flux is practically constant, which are shunt machines and level compound generators.
- The series DC machines cannot be test by Swinburne’s test since they cannot be run on no-load and their flux and speed very greatly.

- Related Questions & Answers
- How to test the efficiency of DC machines? (Hopkinson’s Test)
- Commutation in DC Machines – Resistance Commutation, Voltage Commutation, Compensating Windings
- Types of DC Generator – Separately Excited and Self-Excited DC Generators
- Applications of DC Generators
- Theory of DC Servomotors
- Electric Breaking of DC Motors – Types of Electric Breaking
- Losses in DC Machine – Iron Loss, Copper Loss and Mechanical Losses
- Characteristics of DC Generators – Series, Shunt and Compound
- EMF Equation of DC generator – Derivation and Examples
- Types of Armature Winding of a DC Machine - Lap Winding and Wave Winding
- Characteristics of DC Motors – Shunt, Series and Compound Motors
- Efficiency of a DC Motor – Condition for Maximum Efficiency
- Action of Commutator in DC Generator
- Four Quadrant Operation of DC Motor – Motoring and Breaking Operation
- DC Generator – Demagnetising and Cross Magnetising Conductors

Advertisements