Load test on DC shunt motor

Experiment No.: – 04

Aim of the Experiment: –

               Load test on DC Shunt Motor.

Apparatus Required: –


Sl. No.		NameSpecificationQuantity
1DC shunt motor with spring balance load2 BHP, 1440 rpm, 110V, 18.1A1 no.
2Voltmeter(0-150) V, PMMC1 no.
3Ammeter(0-20) A, PMMC1 no.
4Rheostat(0-80) Ω2 nos.
5TachometerDigital Type1 no.
6Connecting wiresPVC Insulated copperas per required
Table No. 4.1

Circuit Diagram: –

Theory: –

The load test on a DC shunt motor is performed to assess its performance characteristics under different load conditions. The test helps determine parameters such as speed, torque, power, and efficiency of the motor.

Torque Calculation: Torque is the rotational force generated by the motor. It is proportional to the current flowing through the armature windings. The torque can be calculated using the formula:

\[\color\red{Torque \;(T)\; = {K}{t}{I_a}}\] \[\color\red{T\;=\; (W_2-W_1)\times{r}\times{9.81}}\] \[\color\green{Where:}\] \[\color\magenta{ T\;=\; Torque \;in\;(Nm)}\] \[\color\magenta{ Kt\;=\; Torque \;constant\; of\; the\; motor}\] \[\color\magenta{ Ia\;=\; Armature\; current\; (A)}\] \[\color\magenta{W_1\; and\;W_2 \;are\; loads\; in\; kg}\] \[\color\magenta{ r\; is\; the\; effective\; radius\; of\; the\; pulley.}\]

Power Calculation: Power is the rate at which work is done. In the case of a motor, it represents the output power generated by the motor. The power output of the motor can be calculated using the formula:

\[\color\red{Power\; (P)\; = \;\dfrac{2π N T}{60}}\] \[\color\green{Where:}\] \[\color\orange{ P=\; Power\; output\; in\;Watt}\] \[\color\orange{N=\; Speed\; of\; the\; motor\;in\;RPM}\] \[\color\orange{ T=\; Torque\;in\; Nm}\]

Efficiency Calculation: Efficiency is an important parameter that indicates how effectively the motor converts electrical energy into mechanical energy. It is calculated using the formula:

\[\color\red{Efficiency\; (\%)\; = \dfrac{Power\; output}{Power\; input}\times{100}}\] \[\color\green{Where:}\] \[\color\gray{ Power \;output\;=}\] \[\color\gray{\; Power\; delivered \;to\; the \;load}\] \[\color\gray{ Power\; input\;=}\] \[\color\gray{\; Electrical\; power\; input\; to\; the\; motor}\]

By varying the load and calculating the power and efficiency at different load settings, we can observe how the motor performs under different operating conditions.

Procedure: –

  1. Connect all the apparatus as per circuit diagram.
  2. Start motor with the help of starter and take the readings from measuring instruments in no load condition at rated speed.
  3. Gradually increase the load on the pully and take the corresponding readings as per observation table.
  4. During the experiment pour water in the groove of the pulley to keep it cool.

Observation Table: –

 Radius of the pully(r) in meter =…………

Sl. No.Input Voltage (V) in Volts.Armature Current (I) in Amps.Speed (N) in RPMW1 in KgW2 in KgW=(W2-W1) in KgTorque (T) in N-mOutput Power (Po) in wattsInput Power (Pi) in watts% Efficiency
1          
2          
3          
4          
5          
6          
Table No. 4.2

Calculation:

\[\color\red{W\;=\;(W_2-W_1)\; }\color\green{Kg}\] \[\color\red{T\;= \;(W_2-W_1)\times{r}\times{9.81}\;}\color\green{ Nm}\] \[\color\red{P_i\; = \dfrac{2π N T }{ 60} \;}\color\green{watt}\] \[\color\red{P_0\; =\; V\times{I} \color\green{watt.}}\] \[\color\red{\% \;Efficiency\;= \;\dfrac{P_0}{P_i} \times 100}\] \[\color\red{BHP\;= \;\dfrac{P_i}{746}}\]

Draw curve between

  1. BHP vs Torque
  2. Speed vs Torque
  3. BHP vs Speed
  4. BHP vs Efficiency

Conclusion: –

                    To be written by student.

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