Swinburne’s Test

SWINBURNE’S TEST

AIM:

• To conduct Swinburne’s test on DC machine to determine efficiency when working as generator and motor without actually loading the machine. Also plot efficiency curves.

APPARATOUS REQUIRED:

MACHINES DETAILS:

THEORY : 

The power that a dc machine receives is called input power & power it gives out is called output power.

• ie ,The efficiency of a dc machine,
• Efficiency= output/input
• Output=Input-Losses   & Input=Output+ Losses

Swinburne’s test is a no load test conducted on a DC Machine which run as motor at noload& losses of the machine are determined. Once the losses of machine are known,its efficiency at any desired load can be determined in advance. This test only applicable in machines that flux is constant at all loads. In this test, the dc shunt machine is run as a motor on no load with supply voltage adjusted to rated voltage. The speed of the motor is adjusted to rated speed with the help of field rheostat.

PRECAUTIONS:

• The field rheostat of the motor should be in the minimum position at the time of starting and stopping the machine.
• SPST switch should be kept open at the time of starting and stopping the machine.

PROCEDURE:

• Connections are made as per the circuit diagram.
• After checking the minimum position of field rheostat, DPST switch is closed and starting resistance is gradually removed.
• By adjusting the field rheostat, the machine is brought to its rated speed.
• The armature current, field current and voltage readings are noted.
• The field rheostat is then brought to minimum position DPST switch is opened.

PROCEDURE FOR DETERMINING THE RESISTANCE:

• Connections are made as per the circuit diagram.
• Supply is given by closing the DPST switch.
• Readings of Ammeter and Voltmeter are noted.
• Armature resistance in Ohms is calculated as Ra = (Vx1.5) /I

CIRCUIT DIAGRAM

DETERMINATION OF ARMATURE RESISTANCE

TABULAR COLUMN:

SAMPLE GRAPH :

RESULT: