To conduct Swinburne’s test on a given dc shunt machine and to determine efficiency when acting as generator and motor

Sep 24 2023

Aim

To conduct Swinburne’s test on a given dc shunt machine and to determine

It’s efficiency when acting as a generator
It’s efficiency when acting as a motor.

Apparatus Required:

S.no	Name	Range	Type	Quantity
1	Voltmete	(0-300)V	MC	1nos
2	Ammeter	(0-2)A	MC	1 no
3	Ammeter	(0-20)A	MC	1nos
4	Rheostat	400Ω,1.2A	Wire wound	1nos
5	Tachometer	(0-10,000)rpm	Digital	1no
6	Connecting wires	(0-20)A	-	Required

Name plate details:-

Voltage : 220V

Current :19A

RPM : 1500

H.P : 5.0

Circuit diagram:- (a) No-Load Test:

(b) To find Ra:-

Procedure:-

Make the connections as per the circuit diagram.
Initially keep the motor field rheostat in minimum resistance position and SPST switch in closed position.
Give the supply by closing DPST switch and start the motor with the help of 3-point starter
Get the rated speed by varying shunt field rheostat.
Open the SPST switch across the ammeter and note down the voltmeter and ammeter readings.
Switch off the by opening the DPST switch.

To determine armature resistance:

Make the connections as per the circuit diagram.
Switch on dc supply
By increasing the load in steps and note down the voltage and current.
Switch off the by opening the DPST switch.

Tabular columns:

Table 1: No-Load Test

V(volts)	I_a0(amp)	I_f0(amp)
220	1.5	0.65

Table2: Armature Resistance

V(volts)	I(amp)	R_a=(V/I)(ohms)

Table3: Efficiency of dc machine when running as a Motor

I _L	I/P power	Ia (amp)	Ia ²Ra (watts)	Total losses = wc + Ia²Ra	O/P= I/P– Total losses	% η=(O/P)/(I/P)*100
4.75	1045	4.15	32.72	393.62	651.8	62.3
9.5	2090	8.9	150.5	511.41	1518.6	75.5
14.25	3135	13.65	354.01	714.9	2420.6	77.2
19	4180	18.4	643.26	1004.16	3175.8	75.9

Table 4: Efficiency of dc machine when running as a Generator

I _L	O/P power	Ia	Ia ²Ra	Total losses = we + Ia²Ra	I/P= O/P + Total losses	% η=(O/P)/(I/P)*100
4.75	1045	5.35	54.38	415.28	7460.2	71.5
9.5	2090	8.9	150.5	511.41	1518.6	75.5
14.25	3135	13.65	354.01	714.9	2420.6	77.2
19	4180	18.4	643.26	1004.16	3175.8	75.9

Model graph: Draw the graph between output power on x-axis and efficiency on y-axis as shown below.

Calculation:

Constant losses = wc = V*I ₀–Ia0²*R _a

Constant losses = wc= V*(Ia ₀+ I _f0) – I_a0²*R _a

Efficiency when running as a Motor:

I_a= I _L – I _f0

Input = V*I _L

Total losses = Ia ²*Ra + wc

Output = input - losses

%ή = ((o/p)/(i/p))*100

Efficiency when running as a Generator:

I_a=I_L – I _f0

Armature cu loss = I _a²* R _a

Constant losses =. wc

Total losses = I _a ²* R _a+ wc

Input = Output + losses

%ή = ((o/p)/(i/p))*100

Result: The efficiency of a given dc machine is calculated when it is operating as generator as well as motor action by conducting the no-load test.