DC motor ppsx

Enter the nominal data for the DC machine Match the winding designations to the windings Training content: "Connection and starting" z Identify the terminal connections of the motor a

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SH5007-1A Version 1.0 Author: M.Germeroth

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Tel.: +49 2273 567-0

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Training objectives 1

Information page "Alternative Equipment" 3

Voltage control (field control range) 33

Rotation direction and polarity 49

In this course you will acquire practical knowledge regarding the topic of DC

machines

Experiment-based investigations of series-wound, shunt-wound and wound machines are at the focal point of this course and explore such aspects as how the machines function, respond and operate

Training contents

z Motors, generators

z Measurement of armature current, exciter current and voltage

z Nominal data, rating plate

z Rotation reversal

z Magnetic field weakening

z Armature and field resistors

z Power measurement with and without load

Prerequisites

z Fundamentals of electrical machines

z Fundamentals of electrical engineering

z 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

*Alternative equipment to the universal load SO3212-6W

SO3212-5F Field regulator for DC machines* 1

SO3212-6M Load resistor for generator experiments* 1

SO3212-5H Field regulator for generator experiments* 1

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")

Starter (SO3212-6M) and field regulator (SO3212-5H) for DC motors

(connection example: "DC shunt-wound motor")

4

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

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

DC shunt-wound motors

Over the next few pages you will perform the following exercises

pertaining to "DC shunt-wound motors":

z Connection and starting

z Reversing rotation direction

z Speed control

z Load characteristics

8

Enter the nominal data for the DC machine

Match the winding designations to the windings

Training content: "Connection and starting"

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

z Read the nominal data of the motor based on the rating plate

z Connect the motor to the starter

z Be familiar with how the starter works

z Operate the motor with the brake

z Subject the motor to a load

z Measure armature voltage and current

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

Circuit diagram for DC shunt-wound motor

"Connection and starting"

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

z Include an ammeter and voltmeter in the armature circuit

z Switch on the brake too This does not yet subject the motor to any load

10

Set-up for DC shunt-wound motor

"Connection and starting"

Put the shunt-wound motor into operation

Required settings:

z Starter: minimum value (0 Ω)

z DC power supply unit: 220V

Experiment procedure:

z Put the motor into operation and observe its operating response

The motor demonstrates the following response:

z Apply the brake to slow the motor down to nominal speed

z 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?

g The motor rotates at a higher speed than the nominal

speed

g The rotation direction is clockwise

g The rotation direction is anti-clockwise

g The switch-on current is higher than the nominal

current

g The motor rotates at nominal speed

g The current increases with increasing speed

More than one answer may

be correct

n The armature current corresponds approximately to

the nominal current

n The armature current is considerably higher than the

nominal current

n The armature current is considerably smaller than

the nominal current

12

Record a load characteristic

Required settings:

z Starter: maximum value ( Note: 0.3 KW class ~ 47 Ω; 1 KW class ~ 16 Ω)

Experiment procedure:

z The motor should be subjected to the torque loads as set forth in the table

z Measure the armature current and armature voltage under load

z Enter the measured values into the table

500 1000 1500 2000 2500

Which of the following statements apply to the load characteristic?

What is the function of the starter?

g The armature voltage is considerably reduced when

the torque is increased

g The armature current increases linearly with the

torque

g The speed severely drops off once the nominal

torque is reached

g The armature voltage remains practically constant

g The speed remains practically constant (± 3%) in the

range of the nominal torque

g The speed increases at higher torques

More than one answer may

be correct

n The starter is primarily used for speed control

n The starter restricts the switch-on current

n The starter protects the motor from overload during

standard operation

14

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

Note: in the "Classic series" (0.3 kW & 1.0 kW) the rotation direction is

determined by the rotation direction of the brake, i.e if the asynchronous machine rotates clockwise, i.e in the positive direction, the control unit of the brake indicates

a negative rotation direction Thus the rotation direction displayed is always that of the brake

Training content: "Rotation reversal"

z Identify the difference between clockwise and anti-clockwise rotation

z Put the motor into operation in both rotation directions

Assembly instructions: "Rotation Reversal"

Circuit diagram for DC shunt-wound motor

"Rotation Reversal"

z Assemble the circuit as specified in the following circuit diagram and

set-up instructions

z Include an ammeter and voltmeter in the the armature circuit

z Switch on the brake This does not yet subject the motor to any load

16

Set-up for DC shunt-wound motor

z 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

What is the motor's direction of rotation?

z Switch the motor off and modify the circuit as shown by changing the polarity

of the exciter coil

z Turn the motor back on and observe its response

Circuit diagram for DC shunt-wound motor

"Rotation reversal" (reversed rotation direction)

What is the motor's direction of rotation now?

n The motor rotates clockwise

n The motor rotates anti-clockwise

n The motor rotates clockwise

n The motor rotates anti-clockwise

18

Assembly instructions: "Speed Control"

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

Training content: "Speed Control"

z Put the DC motor into operation using the field regulator

z Investigate speed control by modifying the armature current power

z Investigate operation in the field weakening range

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

instructions below

z Include an ammeter and voltmeter in the armature circuit

z Include an ammeter in the exciter circuit

z Switch on the brake This does not yet subject the motor to any load

Set-up for DC shunt-wound motor

"Speed control"

20

Record characteristics "I a and "n" as a function of "U a

Required settings:

z Field regulator: minimum value (0 Ω)

z Brake mode: "Torque Control"

Experiment procedure:

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

z At the same time measure the variables Iaand n and enter the measured

values into the table

Record the characteristic of n" as a function of "M" using the

"ActiveDrive/DCMA" software

Required setting:

z Brake:

{ Industrial series: "PC Mode"

{ Classic series: "Application Mode" ( Note: when starting the

"ActiveASMA" software you will be prompted to select "Application

mode")

z Field regulator: minimum value (0 Ω)

z Adjustable DC power supply unit (armature voltage): 220/190/160V

z DC power supply unit (exciter circuit voltage): 220V

Experiment procedure:

z Start the "ActiveDrive/DCMA" software

z The motor should be subjected to a load equivalent to its nominal torque

z Label the diagram as given in the placeholder

z Record a total of three load characteristics for the three specified armature circuit voltages

z After completing the measurement export the completed diagram with all three characteristics and copy it into the appropriate space below

z Compute the nominal torque of the motor as given by the following equation:

22

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

Record the characteristics of "I f " and "n" as a function of R f

Required settings:

z Brake mode: "Torque Control"

z Field regulator: minimum value (0 Ω)

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

Experiment procedure:

z Switch on the DC power supply

z Vary the Rf value of the field regulator in 3 steps, 0%, 50% and 90% of the maximum value ( Note: 0.3 kW class ~ 2.2 kΩ; 1kW class ~ 680Ω)

z At the same time measure the respective variables If and n for each step and enter the measured values into the table

Rf/Ω 0

Record the characteristic "n" as a function of "M" using the

"ActiveDrive/DCMA" software

Required setting:

z Brake:

{ Industrial series: "PC Mode"

{ Classic series: "Application Mode" ( Note: when starting the

"ActiveASMA" software you will be prompted to select "Application

mode")

z Field regulator: minimum value (0 Ω)

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

Experiment procedure:

z Start the "ActiveDrive/DCMA" software

z The motor should be subjected to a load up to its nominal torque

z Label the diagram as appropriate in the placeholder below

z Record three characteristics are recorded in sequence for 3 different field regulator values (Rf), one each at 0%, 50% and 90% of the maximum setting ( Note: 0.3 kW class ~ 2,2 kΩ; 1 kW class ~ 680 Ω)

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

Placeholder for characteristics n(M), Rf = 0%/50%/90% of the maximum setting

Which statements are true of the speed variation?

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

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

Circuit diagram for DC shunt-wound motor

"Load characteristic"

Training content: "Load characteristic"

z Record the motor's load characteristic

z Calculate the nominal torque

z Determine the highest degree of efficiency

z Recognise how the motor responds to loads

z Assemble the circuit as specified in the following circuit diagram and

set-up instructions

z Include an ammeter and voltmeter in the armature/exciter circuit

z Switch the brake on too This does not yet subject the motor to any load

Set-up for DC shunt-wound motor

"Load characteristic"

28

Record the motor's load characteristics with the aid of the

"ActiveDrive/DCMA" software

Required setting:

z Brake:

{ Industrial series: "PC Mode"

{ Classic series: "Application Mode" ( Note: when starting the

"ActiveASMA" software you will be prompted to select "Application

mode")

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

Experiment procedure:

z Start the "ActiveDrive/DCMA" software

z The motor should be subjected to a load up to 1.5 times its nominal torque

z Label the diagram as given in the placeholder

z 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)

z Before starting the measurement you must have answered the question

concerning the nominal torque, which you should have determined in

the "speed control" experiment

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

z Determine from the diagram the highest degree of efficiency obtainable

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?

30

Separately excited DC shunt-wound generator

z Voltage control (field regulating range)

z Voltage polarity

z Load characteristics

Over the next few pages you will be conducting the following

exercises on a "separately excited DC shunt-wound generator":

32

Assembly instructions: "Voltage Control"

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

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

Circuit diagram for DC shunt-wound generator, separately excited

Training contents: "Voltage Control"

z Connect up the machine as a separately excited DC wound generator

shunt-z Recognise which variables affect the output voltage of the generator

z Determine the output voltage as a function of the speed

z Understand the purpose of the field regulator and how it works

z Assemble the circuit as specified in the following circuit diagram and

set-up instructions

z Include an ammeter and voltmeter in the exciter circuit

z Set the field regulator to the value 0 Ω

z Set the DC power supply to a voltage of 220 V

z In this experiment the brake is used as a drive motor

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

"Voltage control"

34

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

Required settings:

z Brake mode: "Speed Control"

z Field regulator: maximum value ( Note: 0.3 kW class ~ 2.2 kΩ; 1 kW

class ~ 680 Ω)

z DC power supply unit: (exciter circuit) 220 V

Experiment procedure:

z Put the generator into operation

z First run the drive motor up to a speed of 3000 rpm

z Use the field regulator to set the exciter currents specified in the table

z Begin at Ierr.= 0 mA

z Measure the generator voltage UG produced at each speed as you lower the speed step by step (see table)

50 100 150 200 250 300 350

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?

n The voltage results from the inaccuracy of the

measuring instruments being used

n The generator charges up statically due to the

rotating motion of the rotor This surge in charge is

measurable as a low voltage

n This voltage is caused by the residual magnetisation

(remanence) of the exciter field

n The exciter winding's coercive field strength is not

sufficient to generate a low voltage when it is off

g Exciter field voltage

g No-load torque

g Exciter current

g Polarity of the armature winding

More than one answer may

be correct

36