eem 2 dc machines

Course"EEM 2 DC Machines"

Photo: Siemens AG

SH5002-1B Version 2.1

Author: M.Germeroth

Lucas-Nülle GmbH · Siemensstraße 2 · D-50170 Kerpen (Sindorf) Tel.: +49 2273 567-0

www.lucas-nuelle.de

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Copyright © 2005 LUCAS-NÜLLE GmbH. All rights reserved.

LUCAS-NÜLLE Lehr- und Messgeräte GmbH

Siemensstraße 2 D-50170 Kerpen

EEM2 DC machines

Training objectives 1Equipment for 300 W Classic Series 2Information page "Alternative Equipment" 3Safety 5DC shunt-wound motors 7

Connection and starting 9Rotation reversal 17Speed control 23Load characteristic 31

DC shunt-wound generators, separately excited 37Voltage control (field-control range) 39Voltage polarity 45Load characteristic 49

DC shunt-wound generators, self-excited 55Rotation direction and polarity 57Load characteristic 61

DC series-wound motors 67Connection and starting 69Rotation reversal 75Load characteristic 81

DC compound-wound motors 87Load characteristics for various compound ratios 89

Copyright 99

EEM2 DC machines

EEM2 DC machines Training objectives

In this course you will acquire practical knowledge regarding the topic of DC machines. Experiment-based investigations of series-wound, shunt-wound and compound-wound machines are at the focal point of this course and explore such aspects as how the machines function, respond and operate.

Training contents

Motors, generators Series-wound, shunt-wound and compound-wound windings Measurement of armature current, exciter current and voltage Nominal data, rating plate Speed adjustment Rotation reversal Magnetic field weakening Armature and field resistors Power measurement with and without load

Prerequisites

Fundamentals of electrical machines Fundamentals of electrical engineering How to handle measuring instruments

Welcome to the DC machines course. The team from LUCAS-NÜLLE wishes you lots of fun and success in completing the course topics and conducting the experiments. The following pages provide you with an overview of the course contents and the materials and equipment required.

1

EEM2 DC machines Equipment for 300 W Classic Series

*Alternative equipment to the universal load SO3212-6W

SO3636-6V Servo drive/servo brake 0.3 kW 1 SE2662-2A Coupling sleeve 300 W 1 SE2662-2B Coupling guard 300 W 1 SE2672-3D DC multifunction machine 300 W 1 SO3212-6W Universal load for 300 W machines 1 SO3212-6B Starter for DC motor* 1 SO3212-5F Field regulator for DC motor* 1 SO3212-6M Load resistor for generator experiments* 1 SO3212-5H Field regulator for generator experiments* 1 SO3212-5U Power supply for electrical machines 1

SO5127-1ZAnalog/digital multimeter, wattmeter and power factor meter

2

SO5148-1F Set of 47 safety connecting leads 4 mm 1 SO5126-9X Safety connection plugs, 19/4 mm 15SO5126-9Z Safety connection plugs, 19/4 mm, with tap 5

2

EEM2 DC machines Information page "Alternative Equipment"

Universal load (SO3212-6W) for DC motors (connection example: "DC shunt-wound motor")

Starter (SO3212-6B) and field regulator (SO3212-5F) for DC motors (connection example: "DC shunt-wound motor")

3

EEM2 DC machines Information page "Alternative Equipment"

Load resistor (SO3212-6M) and field regulator (SO3212-5H) for DC generators (Connection example: "DC shunt-wound generator")

4

EEM2 DC machines Safety

Basic safety instructions

In all experiments using mains voltages high, life-threatening voltages arise. For that reason use only safety measurement leads and make sure that there are no short-circuits.

It is imperative that all of the devices, which are provided with an earth or where earthing is possible, must be earthed. This is particularly the case for the frequency converter being used.

Always be very careful to check the wiring of the application modules and only switch on the mains voltage after a check has been completed. Whenever possible use a robust current monitoring instrument in the circuit.

Always use shaft-end guards and coupling guards as protection against contact with rotating motor parts

All locally applicable stipulations and standards governing how electrical equipment is handled must be complied with.

5

EEM2 DC machines Safety

General instructions on handling the equipment

Check that the knurled screws at the base of the motor and the coupling sleeves (power grip) on the motor shaft are all securely fastened.

Use shaft and coupling guards. Any prolonged running of the machines when operating under high loads

can subject the machines to excessive heating. The extreme case of the machine being prevented from rotating entirely

may only arise briefly. All of the machines are equipped with a thermal circuit-breaker, which

triggers when the maximum permissible operating temperature is exceeded. These switching contacts are accessible on the terminal board and must always be connected to the corresponding connection sockets of the mains supply and control unit.

All measurements have been recorded using conventional measuring instruments (primarily class 1.5) at the standard mains voltage (230/400V +5% -10% 50Hz) using standard production machines. Experience suggests that measurements will lie within the tolerance range of +/-15% with respect to the specified measurement. For more information on this please refer to VDE0530.

6

EEM2 DC machines DC shunt-wound motors

DC shunt-wound motors

Over the next few pages you will perform the following exercises pertaining to "DC shunt-wound motors":

Connection and starting Reversing rotation direction Speed control Load characteristics

7


8


Enter the nominal data for the DC machine

Match the winding designations to the windings

Training content: "Connection and starting"

Identify the terminal connections of the motor and operate the motor as a shunt-wound motor

Read the nominal data of the motor based on the rating plate Connect the motor to the starter Be familiar with how the starter works Operate the motor with the brake Subject the motor to a load Measure armature voltage and current

UA= ____V

IA= ____A

UE= ____V

IE= ____mA

n= ____rpm

A1/A2 __

B1/B2 __

C1/C2 __

E1/E2 __

D1/D2 __

F1/F2 __

9


Assembly instructions: "Connection and starting"

Note: setting of the DC power supply can only be performed when the motor is connected.

More detailed information on the brake can be found in the corresponding online documentation

Assemble the circuits as specified in the following circuit diagram and set-up instructions

Include an ammeter and voltmeter in the armature circuit Switch on the brake too. This does not yet subject the motor to any

load

10


Circuit diagram for DC shunt-wound motor

"Connection and starting"

11


Set-up for DC shunt-wound motor

"Connection and starting"

Put the shunt-wound motor into operation

Required settings:

Starter: minimum value (0 Ω) DC power supply unit: 220V Multimeter measuring method: arithmetic mean

Experiment procedure:

Put the motor into operation and observe its operating response

12


The motor demonstrates the following response:

Measure the armature current

Required settings:

Brake mode: "Torque Control"


Apply the brake to slow the motor down to nominal speed In the process of braking measure the armature current

Make sure that the brake is not applied so hard that the motor comes to a halt

What is the magnitude of the armature current?

The motor rotates at a higher speed than the nominal speed

The rotation direction is clockwise

The rotation direction is anti-clockwise

The switch-on current is higher than the nominal current

The motor rotates at nominal speed

The current increases with increasing speed

More than one answer may be correct

The armature current corresponds approximately to the nominal current

The armature current is considerably higher than the nominal current

The armature current is considerably smaller than the nominal current

13


Record a load characteristic

Required settings:

Starter: maximum value ( Note: 0.3 kW class ~ 47 Ω; 1 kW class ~ 16 Ω) After starting the motor the starter is set back to 0 Ω.


Gradually increase the motor's load step-by-step until 1.5 times (0.3 kW) or 1x (1 kW) the nominal current and then complete the table

M/Nm n/(1/min) I/A U/V

0.2

0.4

0.6

0.8

1.0

1.2

1.4

0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5M/Nm

0

500

1000

1500

2000

2500

3000

n/m

in¯¹

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

I/A

0

50

100

150

200

250

300

U/V

14


Which of the following statements apply to the load characteristic?

What is the function of the starter?

The armature voltage is considerably reduced when the torque is increased

The armature current increases linearly with the torque

The speed severely drops off once the nominal torque is reached

The armature voltage remains practically constant

The speed remains practically constant (± 3%) in the range of the nominal torque

The speed increases at higher torques


The starter is primarily used for speed control

The starter restricts the switch-on current

The starter protects the motor from overload during standard operation

15


16


Definition of rotation direction If you look at the drive shaft end of the DC shunt-wound machine from the perspective of the working machine (in our case the brake), the rotating direction is positive when it is clockwise. If the motor has two workable shaft ends, then it is the shaft end opposite the cooling vents, collector or slip-rings that is the shaft end which defines the rotation direction.

Training content: "Rotation reversal"

Identify the difference between clockwise and anti-clockwise rotation

Put the motor into operation in both rotation directions

17


Assembly instructions: "Rotation Reversal"


"Rotation Reversal"

Assemble the circuit as specified in the following circuit diagram and set-

up instructions. Include an ammeter and voltmeter in the the armature circuit. Switch on the brake. This does not yet subject the motor to any load.

18



"Rotation Reversal"

Rotation reversal

Required settings:

Starter: minimum value (0 Ω) DC power supply: 220V


Switch on the motor and observe how it responds

Note: setting of the DC power supply can only be performed when the motor is connected.

19


What is the motor's direction of rotation?

The motor rotates clockwise

The motor rotates anti-clockwise

20


Switch the motor off and modify the circuit as shown by changing the polarity of the exciter coil

Turn the motor back on and observe its response


"Rotation reversal" (reversed rotation direction)

What is the motor's direction of rotation now?



21


22


Assembly instructions: "Speed Control"

Note: setting of the DC power supply unit can only be performed when the motor is connected.


Training content: "Speed Control"

Put the DC motor into operation using the field regulator Investigate speed control by modifying the armature current power Investigate operation in the field weakening range

Assemble the circuits as specified in the circuit diagram and set-up

instructions below. Include an ammeter and voltmeter in the armature circuit . Include an ammeter in the exciter circuit. Switch on the brake. This does not yet subject the motor to any load.

23



"Speed control"

24


Set-up for DC shunt-wound motor "Speed control"

Record characteristics "Ia and "n" as a function of "Ua

Required settings:

Adjustable DC power supply (armature circuit voltage): 220V DC power supply unit (exciter circuit voltage): 210V Field regulator: minimum value (0 Ω) Brake mode: "Torque Control"


Reduce the armature voltage in 3 stages via the adjustable DC power supply (220/190/160V)

At the same time measure the variables Iaand n and enter the measured values into the table

25


Record the characteristic of n" as a function of "M" using the "ActiveDrive/ActiveServo" software

Required setting:

Brake: Industrial series: "PC Mode" Classic series: "PC Mode"

Field regulator: minimum value (0 Ω) Adjustable DC power supply unit (armature voltage): 220/190/160V DC power supply unit (exciter circuit voltage): 210V

Ua/V n/(1/min) Ia/A220 2188.0190

160

150 160 170 180 190 200 210 220 230 240Ua/V

0

300

600

900

1200

1500

1800

2100

2400

2700

3000

n/(

1/m

in)

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0.50

Ia/A

26



Start the "ActiveDrive/ActiveServo" software In the menu select Setting -> Operating mode -> Torque control The motor should be subjected to a load equivalent to its nominal torque Label the diagram as given in the placeholder Record a total of three load characteristics for the three specified armature

circuit voltages After completing the measurement export the completed diagram with all three

characteristics and copy it into the appropriate space below Compute the nominal torque of the motor as given by the following equation:

Placeholder for characteristics n(M), Ua=220/190/160V

Record the characteristics of "If" and "n" as a function of Rf

Required settings:

Brake mode: "Torque Control" Field regulator: minimum value (0 Ω) DC power supply unit: (armature & exciter circuit) 220/210V

27



Switch on the DC power supply Vary the value Rf of the field regulator in 3 steps to reach the speed specified

in the table ( Note: 0.3 KW class ~ 2,2 kΩ; 1 KW class ~ 680 Ω) For each setting measure If and transfer the measured values into the table

Record the characteristic "n" as a function of "M" using the "ActiveDrive/ÁctiveServo" software

Required setting:


Field regulator: minimum value (0 Ω) DC power supply unit: (armature & exciter circuit) 220/210V

n(1/min) If/mA2300.02600.03000.0

2300 2400 2500 2600 2700 2800 2900 3000n/(1/min)

0

30

60

90

120

150

180

210

240

270

300

If/m

A

28



Start the "ActiveDrive/ActiveServo" software The motor should be subjected to a load up to its nominal torque Label the diagram as appropriate in the placeholder below One after another 3 characteristic curves are recorded for 3 field regulator

settings (Rf), each one at the respective speeds 2.300 min-1, 2.600 min-1 and 3000 min-1 (rpm) ( Note: 0.3 KW class ~ 2.2 kΩ; 1 KW class ~ 680 Ω)

After completing the measurement export the graph with all 3 characteristics and copy it into the placeholder below

Placeholder for the graph n(M), 2300 min-1/2600 min-1/3000 min-1

Which statements are true of the speed variation?

A reduction of the armature voltage leads to a drop in speed

A reduction of the exciter current leads to a drop in speed

An increase of the armature voltage leads to a drop in speed

A decrease of exciter current leads to an increase in speed


29


30


Setup diagram: "Load Characteristic"

Note: setting of the DC power supply can only be carried out when the motor is connected More detailed information on the brake and the software used can be found in the appropriate online documentation

Training content: "Load characteristic"

Record the motor's load characteristic Calculate the nominal torque Determine the highest degree of efficiency Recognise how the motor responds to loads

Assemble the circuit as specified in the following circuit diagram and set-

up instructions Include an ammeter and voltmeter in the armature/exciter circuit Switch the brake on too. This does not yet subject the motor to any load

31



"Load characteristic"

32



"Load characteristic"

33


Record the motor's load characteristics with the aid of the "ActiveDrive/ActiveServo" software

Required setting:


DC power supply unit: (armature & exciter circuit) 220V


Start the "ActiveDrive/ActiveServo" software The motor is to be loaded up to its nominal torque Label the diagram as given in the placeholder The following parameters should be recorded: The degree of efficiency η(M) (η

=> "Eta"), of the armature current IA, the power output P2 and the speed n(M) Before starting the measurement you must have answered the question

concerning the nominal torque, which you should have determined in the "speed control" experiment

After completing the measurement export the generated graph and copy it into the corresponding placeholder below

Determine from the diagram the highest degree of efficiency obtainable

34


What is the nominal torque?

Placeholder for graph η(M) (η => „Eta“), IA(M), P2(M), n(M)

What is the maximum efficiency "η" for the shunt-wound motor?

MN= ____Nm

η= ____% approx.

35


36

EEM2 DC machines DC shunt-wound generators, separately excited

Separately excited DC shunt-wound generator

Voltage control (field regulating range) Voltage polarity Load characteristics

Over the next few pages you will be conducting the following exercises on a "separately excited DC shunt-wound generator":

37


38


Assembly instructions: "Voltage Control"

Note: setting of the DC power supply can only be carried out when the exciter circuit is connected


Training contents: "Voltage Control"

Connect up the machine as a separately excited DC shunt-wound generator

Recognise which variables affect the output voltage of the generator

Determine the output voltage as a function of the speed Understand the purpose of the field regulator and how it works

Assemble the circuit as specified in the following circuit diagram and set-up instructions

Include an ammeter and voltmeter in the exciter circuit Set the field regulator to the value 0 Ω Set the DC power supply to a voltage of 220 V In this experiment the brake is used as a drive motor

39


Circuit diagram for DC shunt-wound generator, separately excited

"Voltage Control"

40


Set-up for DC shunt-wound generator, separately excited

"Voltage control"

41


Record the characteristic of "UG" as a function of "n" for different exciter currents

Required settings:

Brake mode: "Speed Control" Field regulator: maximum value ( Note: 0.3 kW class ~ 2.2 kΩ; 1 kW

class ~ 680 Ω) DC power supply unit: (exciter circuit) 220 V Multimeter measurement method: arithmetic mean


Put the generator into operation First run the drive motor up to a speed of 2000 rpm Use the field regulator to set the exciter currents specified in the table Begin at Ierr.= 0 mA Measure the generator voltage UG produced at each speed as you lower the

speed step by step (see table)

Ierr.=0mA Ierr.=50mA Ierr.=70mA Ierr.=90mAn/(1/min) Ug/V Ug/V Ug/V Ug/V

20001800160014001200

1200 1300 1400 1500 1600 1700 1800 1900 2000n/(1/min)

0

25

50

75

100

125

150

175

200

225

Ug

(Ier

r=0)

/V

0

25

50

75

100

125

150

175

200

225

Ug

(Ier

r.=

50m

A)/

V

0

25

50

75

100

125

150

175

200

225

Ug

(Ier

r.=

70m

A)/

V

0

25

50

75

100

125

150

175

200

225

Ug

(Ier

r.=

90m

A)/

V

42


Why does the generator produce a low voltage at an exciter current of I = 0 mA?

Which of the following variables have an immediate impact on the generator voltage?

The voltage results from the inaccuracy of the measuring instruments being used

The generator charges up statically due to the rotating motion of the rotor. This surge in charge is measurable as a low voltage

This voltage is caused by the residual magnetisation (remanence) of the exciter field

The exciter winding's coercive field strength is not sufficient to generate a low voltage when it is off

Exciter field voltage

Speed

No-load torque

Exciter current

Polarity of the armature winding


43


44


Assembly instructions: "Voltage Polarity"

Note: setting of the DC power supply unit can only be performed when the exciter circuit is connected


Training contents: "Voltage Polarity"

Recognise the relationship between the polarity of the connection of the exciter winding, the rotation direction of the generator and how they relate to the resulting generator voltage


instructions below Include an ammeter and voltmeter in the exciter circuit. Set the field regulator to the value 0 Ω Set a voltage of 220 V on the DC power supply In this experiment the brake is used as a drive motor

45


Circuit diagram for DC shunt-wound generator, separately excited

"Voltage polarity"

46



"Voltage polarity"

47


Properties of a generator when the polarity of the exciter winding is reversed and when the rotation direction is reversed

Required settings:

Brake mode: "Speed Control" Field regulator: minimum value (0 Ω) DC power supply unit: (exciter circuit) 220 V


Put the generator into operation First run the drive motor up to a speed of 2000 rpm Measure the generator voltage UG Now change the polarity of the exciter winding and then the rotation direction

of the drive motor Measure the generator voltage UG after each modification

Which of the following statements is true?

The polarity of the generator voltage is independent of the generator's rotation direction

The polarity of the exciter winding and the rotation direction of the generator are determined by the polarity of the generator voltage

The polarity of the generator voltage cannot be changed as it is fixed to the same polarity by the manufacturer

48


Training contents: "Load Characteristics"

Record and interpret the load characteristics of a DC shunt-wound generator

Understand the relationship between the generator voltage, armature current, exciter current and speed

49


Assembly instructions: "Load Characteristics"

Note: setting of the DC power supply unit can only be performed when the exciter circuit is connected


Assemble the circuit as specified in the circuit diagram and set-up

instructions Include an ammeter and voltmeter in the exciter/armature circuit The armature circuit is to be ted to the load resistor In this experiment the brake is used as a drive motor

50


Circuit diagram for shunt-wound generator, separately excited

"Load Characteristics"

51



"Load characteristics"

52


Record the load characteristics of the generator with various exciter currents

Required settings:

Brake mode: "Speed Control" DC power supply unit: (exciter circuit) 220V Field regulator: minimum setting (0 Ω) Load resistor: maximum ( Note: 0.3 kW class ~ approx. 1 kΩ; 1 kW class ~

approx. 440 Ω)


The drive motor is to be run up to a speed of 2000 rpm with the generator operating without a load (load resistor set to maximum)

Record the load characteristics based on the armature currents specified in the table with 2 different nominal exciter currents (50% and 100% of the nominal exciter current)

Measure the variables UG (generator voltage) and P2 (power output) when the armature current IG is increased step by step

Increase the armature current by reducing the load resistance Calculate the power output and enter all the measured values into the tables

The electrical power output is computed as follows:

P2=UG*IG; UG[V], IG[A], P2[W]

53


100% of nominal exciter current

50% of nominal exciter current

Ig/A 0.30 0.60 0.80 1.00 1.20 1.40Ug/VP2/W

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5Ig/A

0

50

100

150

200

250

300

350

Ug

/V

0

50

100

150

200

250

300

350

P2

/W

Ig/A 0.30 0.60 0.80 1.00 1.20 1.40Ug/VP2/W

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5Ig/A

0

50

100

150

200

250

300

350

Ug

/V

0

50

100

150

200

250

300

350

P2

/W

54

EEM2 DC machines DC shunt-wound generators, self-excited

DC shunt-wound generator, self-excited

Rotation direction and polarity Load characteristics

Over the next few pages you will be conducting exercises on a "self-excited DC shunt-wound generator":

55


56


Assembly instructions: "Rotation Direction and Polarity"

More detailed information regarding the brake can be found in the corresponding online documentation

Training content: "Rotation Direction and Polarity"

Recognise how the generator voltage results from the polarity of the exciter winding and the generator's rotation direction


instructions below Include an ammeter and voltmeter in the armature circuit Include an ammeter in the exciter circuit Connect the armature circuit to the load resistor In this experiment the brake is used as a drive motor

57


Circuit diagram for DC shunt-wound generator, self-excited

"Rotation direction and polarity"

58


Set-up for DC shunt-wound generator, self-excited

"Rotation direction and polarity"

Properties of the generator when rotation direction is reversed

Required settings:

Brake mode: "Speed Control" Field regulator: minimum setting (0 Ω) Load resistor: maximum ( Note: 0.3 kW class ~ 1 k Ω; 1 kW class ~ 440 Ω) Multimeter measurement method: arithmetic mean

59



Put the generator into operation by running the drive motor up to a speed of approx. 2000 rpm

Measure the generator voltage UG and enter this into the box corresponding to the rotation direction

Now reverse the rotation direction of the drive motor Finally measure the generator voltage UG again and enter this value again into

the corresponding box

The generator voltage for anti-clockwise rotation of the generator is:

The generator voltage for clockwise rotation of the generator is:

Which of the following statements is true of the generator voltage?

UG= ____V

UG= ____V

The amplitude of the generator voltage is the same for both rotation directions

When rotating clockwise the ampltiude of the generator voltage is the highest

For both rotation directions the generator voltage is zero

During clockwise rotation the amplitude of the generator voltage is somewhat lower than for anti-clockwise rotation

60



More detailed information on the brake can be found in the corresponding online

documentation

Training content: "Load Characteristics"

Record and interpret the load characteristics for a self-excited DC shunt-wound generator

Understand the relationship between the generator voltage, exciter current and speed


instructions below Include an ammeter and voltmeter in the armature circuit Include an ammeter in the exciter circuit Connect the armature circuit to the load resistor In this experiment the brake is used as a drive motor

61


Circuit diagram for DC shunt-wound generator, self-excited

"Load characteristics"

62


Set-up for DC shunt-wound generator, self-excited

"Load Characteristic"

63


Record the load characteristic of the generator

Required settings:

Brake mode: "Speed Control" Field regulator: minimum setting (0 Ω) Load resistor: maximum ( Note: 0.3 kW class ~ approx. 1 kΩ; 1 kW class ~

approx. 440 Ω)


Put the generator into operation First run the drive motor up to a speed of 2000 rpm Make sure that you have the correct rotation direction of the motor, as

determined in the experiment "rotation direction and polarity" Now the nominal exciter current must be set using the field regulator Reduce the resistance in consistent intervals In the process measure the generator voltage UG, the armature current IG and

use these measurements to compute the power output P2 Transfer all of these values into the table

64


Select those statements that are true about the load characteristic

Ug/V Ig/A P2/W

0 20 40 60 80 100 120 140 160 180 200U/V

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

Ig/A

0

10

20

30

40

50

60

70

80

90

100

P2

/W

P2 is dependent on the load resistor

As R(A) rises P2 also increases continuously

The characteristics for P2 & IG have the same pattern in terms of their curve

The generator voltage UG drops with increasing load

The armature current is constant


65


66

EEM2 DC machines DC series-wound motors

DC series-wound motors

Connection and starting Reversing rotation direction Load characteristics for various voltages

Over the next few pages you will be conducting the following exercises on "DC series-wound motors":

67


68


Assembly instructions: "Connection and Starting"

Note: setting of the DC power supply unit can only be carried out when the motor

is connected


Training content: "Connection and Starting"

Identify the terminal connections of the motor and operate the motor as a shunt-wound motor

Put the motor into operation with the brake Connect the motor to the starter Be familiar with how the starter works Measure the motor voltage and the motor current Determine the degree of efficiency

Assemble the circuit as specified in the following circuit diagram and

set-up instructions Include an ammeter and voltmeter in the motor circuit Switch on the brake too. This does not yet subject the motor to any load

69


Circuit diagram for DC series-wound motor

"Connection and Starting"

70


Set-up for of the DC series-wound motor

"Connection and Starting"

71


Determine the nominal efficiency

Required settings:

Brake mode: "Torque Control" ( Note: The brake should definitely be active) Starter: minimum value (0 Ω) DC power supply unit: 220 V Multimeter measurement method: arithmetic mean


Brake the motor down to its nominal torque In the process measure the motor current Use the provided equation to compute the efficiency of the motor based on the

rated data and the measured variables

Make sure that the motor is not operated without any load, as otherwise the motor could start to "race"

The efficiency is defined as:

P2=Mn*ω, P1=UM*IM, ω=2*π*n

What is the efficiency "η" of the series-wound motor with a nominal load?

η=P2/P1

η= ____% approx.

72


Record a load characteristic (with starter)

Required settings:

Brake mode: "Torque Control" (the brake should definitely be active) Starter: minimum value (0 Ω) DC power supply unit: 220 V


Brake the motor down to 0.5 times its nominal torque Now adjust the starter in 5 steps from 0 up to 100% of its maximum value (

Note: 0.3 kW class ~ 47 Ω; 1 kW class ~ 16 Ω) At the same time measure the motor current and voltage Transfer the measurement values into the table

U/V n/(1/min) I/A

150 160 170 180 190 200 210 220 230 240 250U/V

1500

1600

1700

1800

1900

2000

2100

2200

2300

2400

2500

n /(

1/m

in)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

I/A

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Definition of rotation direction If you look at the drive shaft end of the DC shunt-wound machine from the perspective of the working machine (in our case the brake), the rotating direction is positive when it is clockwise. If the motor has two workable shaft ends, then it is the shaft end opposite the cooling vents, collector or slip-rings that is the shaft end which defines the rotation direction.

Training content: "Rotation Reversal"

Recognise the difference between clockwise and anti-clockwise rotation

Put the motor into operation in both directions

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Assembly instructions: "Rotation Reversal"

Note: setting of the DC power supply unit can only be performed with the motor connected

More detailed information can be found in the corresponding online documentation


instructions below Include an ammeter and voltmeter in the motor circuit Switch on the brake too. This does not yet subject the motor to any

load Set the starter to a setting of 0 Ω Set a voltage of 220 V on the DC power supply unit

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"Rotation Reversal"

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Set-up for DC series-wound motor

"Rotation Reversal"

Determining the respective rotation direction

Required settings:

Brake mode: "Torque Control" (the brake should definitely be active) Starter: maximum setting ( Note: 0.3 kW class ~ 47 Ω; 1 kW class ~ 16 Ω) DC power supply unit: 220V

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Put the motor into operation and observe the following

Make sure that the motor is not operated without any load, as otherwise it could "race"

What is the motor's rotation direction?

Now modify the circuit diagram as shown on the next page:



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"Rotation Reversal"

(reversed rotation direction)

What is the motor's rotation direction now?


The motor rotates counterclockwise

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Note: setting of the DC power supply unit can only be performed when the motor is connected


Training content: "Load Characteristics"

Analyse and understand the relationship between the load of the series-wound motor and its speed and armature current


instructions below Include an ammeter and voltmeter in the motor circuit Switch on the brake too. This does not yet subject the motor to any load

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Set-up for DC series-wound motor


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Record the load characteristics of the motor using the "ActiveDrive/ActiveServo" software

Required setting:

Brake: Industrial series: "PC Mode" Classic series: "PC Mode" ActiveDrive / ActiveServo: Setting -> Operating mode -> Speed control

DC power supply unit: (motor circuit) 220 V


Start the "ActiveDrive / ActiveServo" software Make sure that you start the brake at 3000 min-1 prior to switching on the

motor, as otherwise the motor might "race" The motor should be braked from 3000 min-1 to 1600 min-1 in 20 discrete

steps using the ramp function Label the graph as given in the placeholder below In the first graph the following parameters should be plotted: the motor current

I(M), the motor voltage U(M) and the torque M(M) In the second graph the following parameters are to be plotted: the consumed

electical power and the mechanical output power (P1(M), P2(M)) as well as the resulting efficiency η(M) (η => "Eta")

After completing the measurements export the generated graphs and copy them into the placeholders below

Determine the highest possible efficiency from the second graph

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Placeholder for graph U(M), I(M), M(M)

Placeholder for graph η(M) (η => "Eta"), P1(M), P2(M)

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What is the maximum efficiency "η" for the series-wound motor?

Which of the following statements regarding the load graphs are true?

Why is it imperative that a series-wound motor is never operated without load?

η= ____% approx.

The exciter field and the armature current are low when the loads are also low

The armature current increases linearly with the load

The efficiency "η" is constant

The speed is inversely proportional to the torque

Under low load the speed and armature current levels increase

The rotation speed drops off severely with increasing load


Without a load the speed drops off at a rapid rate

Without a load the motor can start to "race"

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EEM2 DC machines DC compound-wound motors

DC compound wound motor

Load characteristics for different compound ratios

On the next page the following exercise will be conducted on the DC compound-wound motor:

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Training content: "Load Characteristics for Different Compound Winding Ratios"

Identify the terminal connections of the motor and operate the motor as a DC compound-wound motor

Put the motor into operation with the brake Record the load characteristics for different series-wound

components Identify the difference between over-compounded, normal and

under-compounded motors Compare the response of acompound-wound machine with

series and shunt-wound machines

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Note: setting of the DC power supply unit can only be performed when the motor is connected


Circuit diagram for compound-wound machine

"Load characteristics for different compound winding ratios"

(100% series-wound component – "over-compounded“)

Assemble the circuit as specified in the following circuit diagram and

set-up instructions Include an ammeter and voltmeter in the motor circuit Switch on the brake too. This does not yet subject the motor to any

load

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Set-up for compound wound machine

"Load characteristic for different compound winding ratios"

(100% series-wound component – " over-compounded“)

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Record the load characteristics of the motor with various compound ratios using the software "ActiveDrive/ActiveServo"

Required settings:


DC power supply unit: (motor circuit) 220 V Multimeter measurement method: arithmetic mean


Start the "ActiveDrive/ActiveServo" software The motor should be subjected to a load up to 1.5 times its nominal torque Label the graph as specified in the placeholder below You should perform three measurements for different compound winding

ratios (100%, 70%, 30% series-wound component) recording two graphs, each with different parameters

In the first graph the following parameters are to be plotted: the motor current I

(M), the motor voltage U(M) and the speed n(M) In the second graph the following parameters should be plotted: consumed

electrical power and the mechanical power output (P1(M), P2(M)), as well as the resulting degree of efficiency η(M) (η => „Eta“)

Export the plotted graph and copy it into the placeholder below Determine the optimum efficiency in each case from the second graph

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Placeholder for graph U(M), I(M), n(M) (100% series-wound component – "over-compounded“)

Placeholder for graph η(M) (η => „Eta“), P1(M), P2(M)

(100% series-wound component – "over-compounded“)

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(70% series-wound component – "normal compounded“)

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Placeholder for graph U(M), I(M), n(M) (70% series-wound component – "normally compounded“)

Placeholder for graph η(M) (η => "Eta"), P1(M), P2(M)

(70% series-wound component – "normally compounded“)

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(30% series-wound component – "under-compounded“)

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Placeholder for graph U(M), I(M), n(M) (30% series-wound component – "under-compounded“)

Placeholder for the graph η(M) (η => „Eta“), P1(M), P2(M)

(30% series-wound component – "under-compounded“)

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Which compound winding ratio produces the highest efficiency "η"?

What is the optimum efficiency "η" of the compound-wound motor at the appropriate compound winding ratio?

Based on the graphs, which statements are true of the compound wound motor?

100% shunt-wound/70% series-wound



η= ____% approx.

The speed of the compound-wound motor under load drops more severely than for the shunt-wound motor regardless of the compound winding ratios

The compound-wound motor can start to "race" in the no-load state just like the series-wound motor

The higher the series-wound component, the lower the speed drop under load

The smaller the series-wound component, the lower the speed drop under load

If the polarity of the series-wound winding is reversed, the speed increases, due to the fact that the shunt-wound winding is weakened

When the polarity is reversed in the series-wound winding, the speed increases because the field of the shunt wound winding is amplified


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EEM2 DC machines Copyright

Copyright © 2004-2006 LUCAS-NÜLLE GmbH.

This course "EEM 2 DC machines" is protected by copyright. All rights pertaining thereto are reserved. Any reproduction of the document as a file or in written form be it photocopy, microfilm or any other method or conversion into a machine-compatible language, in particular for data processing systems, without the expressed written approval of the LUCAS-NÜLLE GmbH is strictly forbidden.

The software as described above is made available on the basis of a general licensing agreement or in the form of a single license. The use or reproduction of the software is only permitted in strict compliance with the contractual terms stated therein.

If changes have been performed in a manner which was not strictly authorised by the LUCAS-NÜLLE GmbH, any product liability or warranty claims pertaining thereto are null and void.

Congratulations! This is the last page. You have completed the course "EEM 2 DC

machines".

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