This master's thesis describes the development of a PLC-based motor test bed for measuring torque and temperature. The test bed hardware includes an induction motor, electrical brake, frequency inverter, torque and tachogenerator sensors. The PLC controls the test bed and monitors alarms. Methods for measuring torque include a torque sensor and torque comparison. Temperature of the electrical brake coil is measured to monitor load. The test bed outputs signals are analyzed to test the sensors and modules.

1. PLC Based Control of a Motor
Test Bed and Torque
Measurement
1
Master Thesis Presented by:
Hizbullah Khan (23559)
Supervisors:
Dr.-Ing., Professor Bernd Altmann
Dr.-Ing., Professor Franz Brümmer

2. Presentation Outline
• Task
• Hardware
• Motor Test Bed Overview
• Block Diagram
• Alarm System and Handling Alarms
• Electrical Brake
• Load/Brake Coil Temperature Measurement
• Torque Measurement
• Test Bed Output Signals
Motor Test Bed
2

3. Task
• Temperature measurement of the load coil
• Torque measurement via different methods
• Torque comparison
• Different alarm conditions
• Study sensors and modules output
Motor Test Bed
3

4. Motor Test Bed Hardware
• Eaton XC-CPU 101 Modular PLC (Easy Soft CoDeSys v2.3.5)
• 3 Phase Induction Motor (2 pole pairs)
• Electrical Brake (Eddy current principle)
• Frequency Inverter
• Torque Sensor (2.5± 2)V measures Toque upto 7.1 N.m.
• Tachogenerator (±2.85V)
• Voltage Transducers
• Current Transducers
• Current Monitor
• Analogue Indicators
Motor Test Bed
4

5. Motor Test
Bed Overview
5

6. Block Diagram
Motor Test Bed
6

7. Motor Test Bed Alarms
Motor Test Bed
7
• Three predefined alarm conditions
1. Inverter Power Off Alarm
2. Cover Lock Failure Alarm
3. Load Temperature Exceed Alarm

8. Handling Alarms
Motor Test Bed
8
• Acknowledging the alarm before the failure is
sorted out (timing diagram)

9. Handling Alarms
Motor Test Bed
9
• Acknowledging the alarm after the failure is
sorted out (timing diagram)

10. Handling Alarms
Motor Test Bed
10
• Acknowledging the load temperature exceed
alarm (timing diagram)

11. Electrical Brake
• Electrical brake works on eddy current
principle
• A non ferromagnetic metal disc is placed in between the
coils of the brake. Once the current starts flowing through
the coil and the metal disc is rotating in between the coils,
this movement of the disc changes the magnetic flux of
the coils and creates eddy currents in the disk.
• These eddy current creates an opposing magnetic field
to that of the coils magnetic field and provides the
braking force by resisting the rotation. (Lenz’s Law)
Motor Test Bed
11

12. Electrical Brake Coil Temperature Measurement
• Current flow of up to 3.6 A through the brake coil
• The resistance of the coil is directly proportional to heat produced in the coil
• Measuring the temperature of the copper coil
Rearranging:
Motor Test Bed
12
[1 ( )]
R R T T
coil amb coil amb

  
24.31 236.73
T R
coil coil
 
 
,
. . 0. ,
( . . 0.00 0 / ),
R Current resistance of the coil of the brake
coil
R Resistance of the coil at ambient temperature i e 1 6 Ohms
amb
Temperature coefficient of copper i e 4 41 C
T Current temperature of
coil






,
(21 )
the coil of the brake
T Ambient temperature C
amb 


13. Electrical
Brake
Interface
13
24.31 236.73
T R
coil coil
 
can be found using
Ohm’s law
Rcoil

14. Current Transducer i/p Scaling
Motor Test Bed
14
0 2 4 6 8 10 12
0
500
1000
1500
2000
2500
3000
3500
4000
4500
(0, 0)
(5, 2047)
(10, 4095)
U_CT
D_in
0 500 1000 1500 2000 2500 3000 3500 4000 4500
0
1
2
3
4
5
6
(0, 0)
(4095, 5)
D_in
Current flowing
via brake (A)
0.00122
brake in
I D


15. Signal Adopter i/p Scaling
Motor Test Bed
15
0 2 4 6 8 10 12
0
500
1000
1500
2000
2500
3000
3500
4000
4500
(0, 0)
(5, 2047)
(10, 4095)
U_SA
D_in
0.01075
brake in
U D

0 500 1000 1500 2000 2500 3000 3500 4000 4500
0
5
10
15
20
25
30
35
40
45
(0, 0)
(40, 4095)
D
Voltage provided
to the brake (V)

16. Current Transducer Block Diagram
Motor Test Bed
16
• Configurable Module via DIP switches
• Output Voltage: 0…10V, 2…10V, -10…10V, 0…5V, 1…5V, -5…5V,
• Output Current: 0…20mA, 4…20mA

17. Current Transducer Output
17

18. Programming Flow
Diagram
• CT problem
Compensated in
programming
18

19. Torque Measurement
• Torque sensor
• Predesigned mechanical setup
• Optical sensors and counters (Hooke’s Law
principal)
Motor Test Bed
19

20. Torque Comparison
Motor Test Bed
20
0 10 20 30 40 50 60 70 80 90 100 110 120
0
0,1
0,2
0,3
0,4
0,5
0,6
0,7
0,8
0,9
1
Torque Sensor
Torque (Mechanical Display)
Field Frequency (Hz)
Torque (N.m.)

21. Test Bed Output Signals
Motor Test Bed
21
• Tachogenerator Signal without low pass filter (CW rotation)

22. Test Bed Output Signals
Motor Test Bed
22
• Tachogenerator Signal with low pass filter (CW rotation)

23. Test Bed Output Signals
Motor Test Bed
23
• Tachogenerator Signal with low pass filter (CCW rotation)

24. Test Bed Output Signals
Motor Test Bed
24
• Torque Sensor Signal with low pass filter (Motor Stopped)

25. Test Bed Output Signals
Motor Test Bed
25
• Torque Sensor Signal with low pass filter (Torque present, CW rotation)
Measuring a torque of 0.8549, (0.28073 ) 2.5
TS
U T
  

26. .
Thank you
Questions, Comments ?
26
Motor Test Bed