EEL 3136

Electrical Drives

MD1

DC MOTOR SPEED CONTROLER

Note: On-the-spot evaluation is carried out during or at the end of the experiment. Students are advised to read through this lab sheet before doing experiment. Your performance, teamwork effort, and learning attitude will count towards the marks.

Caution

  1. This experiment deals with voltage supply of 400V,50Hz
  2. Students will be provided with a technical manual of the system.

OBJECTIVE

To analyze armature voltage control of a direct-current separately excited motor, under various loading conditions.

PROCEDURES:

A: Armature Voltage Approach

  1. Arrange the instruments as shown in Fig. 1.

Fig. 1: Arrangement of instruments

  1. Connect as per the circuit diagram shown in Fig. 2.

Fig. 2: Circuit diagram

  1. Before starting the motor, adjust the operating elements of the control unit in the following manner:

Type of power / 300 W
Operating switch on position: / off
Switch “nconst, Mconst “ position: / Mconst.
Switch “Torque range” position: / 10 Nm
Switch “speed range” position: / 3000
  • Switch on the control unit with the master switch.
  • Press the reset button. Now the red LED should not be lit anymore, otherwise check the following:

-the coupling hoop guard

-the hoop guard for the shaft end cover

-the jack plug for the motor temperature control (probably has not been plugged in)

-the motor ( perhaps the motor is too hot).

NOTE : Always monitor both the armature and field current drawn by the motor, the values MUST NOT exceed the rated stated on the name plate. Write down the rated armature and field current values of the motor.

Rated Armature current : ………………A

Rated Field Current :……………….A

  1. Adjust the Imax (67 10 402) at 2 A
  2. Adjust the armature voltage, VA to 100V
  3. Adjust the given load at the control unit of the pendulum machine by pressing the push button “down”. When exceeding the selected value, press push button ”up”.
  4. Read the corresponding values measured. Enter the measured values on the Table 1.
  5. Repeat steps 3 and 4 above, but this time, control the armature voltage to maintain the speed for all the loading conditions.
  1. Read the corresponding values measured. Enter the measured values on the Table 2.
  1. Calculate both the mechanical and electrical power values for each condition in Table 1 and 2.

Table 1

M in Nm / >0 / 0.4 / 0.8 / 1.2 / 1.6 / 2.0
n (rpm)
IA (A)
IE (A)
VA (V) / 100 / 100 / 100 / 100 / 100 / 100
VE (V)
Pmech (W, Calculate)
Pelec. (W, Calculate)

Table 2

M in Nm / >0 / 0.4 / 0.8 / 1.2 / 1.6 / 2.0
n (rpm)
IA (A)
IE (A)
VA (V)
VE (V)
Pmech (W, Calculate)
Pelec. (W, Calculate)

B: Field Weakening Approach

  1. Set the armature voltage to rated value of the motor. Set load to 0 Nm. Record the speed value.

Speed, n : ………………….rpm

Armature voltage, VA : …………………V

  1. Now adjust the load to 1.2 Nm and record the speed

Speed, n : ………………….rpm

  1. Now, reduce the voltage VE until speed of the motor is equivalent to value recorded in step 1.

Speed, n : ………………….rpm

Armature voltage, VA : …………………V

Armature voltage, VE : …………………V

QUESTIONs

  1. Analyze results obtained in Table 1 and 2. Special focus must be given on the performance of motor with speed controller. You MUST support your analysis using appropriate graphs.
  1. Analyze results obtained in part B, for field weakening approach.

Updated 31 March 2014…gr