The Swinburne Test is a method for determining the performance characteristics of direct current (DC) devices like generators and motors. This test, named for its author, Thomas Swinburne, a renowned electrical engineer from the early twentieth century, gives useful information on the efficiency and overall health of DC equipment. If you are interested in electrical engineering, particularly DC machines, this test is very important. In this essay, we will go over the Swinburne Test, including its aim, methodology, and significance in the evaluation of direct current machines.

What is Swinburne’s Test?

Swinburne’s test (named after James Swinburne) is an indirect method for evaluating a DC shunt or DC compound motor. During this test, the motor is unloaded. As a result, this kind of testing is also known as No-load Testing. The Swinburne’s test is extremely useful for very huge machines that cannot be tested under actual load. As a result, this technique contributes to the understanding of the performance characteristics of big DC machines.

Swinburne’s Test Circuit Diagram

Swinburne’s test is used to calculate the motor’s losses and efficiency at any specified load. In this test, the DC machine functions as a motor with no load. The stimulation is delivered to the motor so that it can function at rated voltage and speed. The connection diagram for Swinburne’s test is illustrated in the image below.

This is an indirect approach for testing a DC machine. It’s named after Sir James Swinburne. Swinburne’s test is the most widely used and easy way of checking shunt and compound wound DC devices with constant flux. In this test, the machine’s efficiency at any load is predetermined. We may use the machine as a motor or generator. In this type of testing, no load losses are assessed independently, allowing us to calculate efficiency.

The circuit connection for Swinburne’s test is illustrated in the diagram below. The speed of the machine is regulated to the rated speed using the shunt regulator R, as illustrated in the figure.

Swinburne Test for DC Machine

The Swinburne’s test may be used to determine the losses in DC machines when there is no load. DC machines are just motors or generators. This test is only relevant to big shunt DC devices with constant flux. It is relatively simple to determine the machine’s efficiency in advance. This test is cost-effective since it needs little input power with no load.

Swinburne Test for DC Shunt Motor

Swinburne’s test on a DC shunt motor may be used to determine machine losses when there is no load power. The motors’ losses include armature copper losses, iron losses in the core, friction losses, and winding losses. These losses are computed independently, and efficiency may be predetermined. The shunt motor’s output is zero with no-load power input, hence this input no-load is utilized to provide the losses. Because the change in iron losses cannot be calculated from no-load to full-load, and the change in temperature increase cannot be detected at full load.

Calculation of Efficiency

Let I₀ be the no-load current (which may be measured by an ammeter A₁).

I_sh is the shunt field current (it may be measured with ammeter A₂).

The no-load armature current = ( I₀ – I_sh)

The supply voltage (V). As a result, the power input with no load equals V I₀ watts.

Swinburne’s test requires no load power input, merely to provide losses. The losses that occur in the machine mostly include:

• Iron loss in the core
• Friction and winding losses.
• Armature copper loss.

Swinburne’s test determines that the machine’s no load mechanical output is zero, hence the no load input power is simply utilized to provide losses.

The armature copper loss is = ( I₀ – Ish)² R_a

the armature resistance (Ra).

Now, to calculate the constant losses, we must remove the armature copper loss from the no-load power input.

Constant losses W_c = V I₀ – ( I₀ – I_sh )² R_a

After computing the no-load constant losses, we may compute the efficiency at any load.

Let I be the load current used to calculate the machine’s efficiency.

When the machine is running, the armature current (Ia) will equal (I – Ish). When the machine motoring

And I_a = ( I + I_sh ) when the machine is generating.

Efficiency of Motor

Efficiency of a DC Machine When running as a motor, 

load current = I_L in Ampere.

Load voltage = V in Volt.

Total input power = V I_L in Watts.

The total constant losses are the same as calculated above.

Total constant losses: P_C = V I_O – (I_O – I_sh)² R_a 

Armature copper loss = (I₀ – I_Sh)² R_a

Total losses: P_T = P_C + (I₀ – I_Sh)² R_a = V I₀ – (I0-I_Sh)² R_a + (I₀-I_Sh)² R_a

Output = Input-P_T = V I_L-P_T

Efficiency of a Motor

η_g = Output / Input x 100

η_g = ( V IL ) / ( V IL + PT ) x 100%

Efficiency of Generator 

Efficiency of DC machines. When running as a generator, the load current (Amp) is supplied at the load voltage (volts).

Generator output = V I_L – Watts.

Armature copper loss = I_a² R_a.

For generator: I_a = I_L + I_Sh.

Therefore, armature copper loss = (I_L + I_Sh)² R_a.

Constant loss: P_C = V I₀ – (I₀ – I_Sh)² R_a.

Therefore, total losses in the generator = P_T = P_C + (I_L + I_Sh)² R_a.

P_T = V I₀ – (I₀ – I_Sh)² Ra + (I_L + I_Sh)² R_a.

Input = output + all losses.

Input = V I_L + P_T, indicating generator efficiency.

Generator Efficiency

η_g = Output / Input x 100

η_g = ( V I_L ) / ( V I_L + P_T ) x 100%

Differences Between Swinburne’s Test and Hopkinson’s Test