Siemens Microscope & Magnifier A1 User manual

MICROMASTER

User Documentation

Applications Handbook Issue A1

ii MICROMASTER Applications Handbook

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MICROMASTER Applications Handbook iii

Valid for A1 Release

Inverter Type Control Version

MICROMASTER MM4

Issue: A1

MICROMASTER

Applications Handbook

User Documentation

Introduction

1

Siemens Drives

Product Range

2

Selecting a Drive

3

Getting Started

4

Simple Applications

5

Electromagnetic

Compatibility

6

Real Applications

7

Advanced

Applications

8

Options

9

Appendices

A

B

Index

iv MICROMASTER Applications Handbook

International English Contents

MICROMASTER Applications Handbook v

Table of Contents

1 Introduction ............................................................................................................... 1

1.1 What is a Variable Speed Drive? ................................................................................ 1

1.2 The Variable Frequency Inverter................................................................................. 3

2 Siemens Drives Product Range............................................................................... 7

3 Selecting a Drive ....................................................................................................... 9

3.1 Overall Considerations ................................................................................................ 9

3.2 Supply Side Requirements.......................................................................................... 9

3.3 Motor limitations .......................................................................................................... 12

3.4 Load Considerations ................................................................................................... 13

3.5 Acceleration and Braking requirements ...................................................................... 15

3.6 Environmental Considerations .................................................................................... 16

4 Getting Started with an Inverter............................................................................... 17

4.1 Mounting the Inverter .................................................................................................. 17

4.2 Cooling ........................................................................................................................ 17

4.3 Wiring up the Inverter .................................................................................................. 17

4.4 First Switch On ............................................................................................................ 20

5 Applications and Possibilities ................................................................................. 21

5.1 Using a Potentiometer with the Analog Input.............................................................. 21

5.2 Using all the Digital Inputs........................................................................................... 21

5.3 Selecting and Using the Fixed Frequencies ............................................................... 22

5.4 Using other digital input features................................................................................. 22

5.5 Using the control outputs ............................................................................................ 23

5.6 Current Limit and Protection Systems......................................................................... 24

5.7 Other Protection Features........................................................................................... 24

5.8 Some Additional Features........................................................................................... 25

Contents International English

vi MICROMASTER Applications Handbook

6 Electromagnetic Compatibility (EMC)..................................................................... 29

6.1 What is EMC? ............................................................................................................. 29

6.2 Minimising the problem of EMI.................................................................................... 29

6.3 EMC Rules and Regulations ....................................................................................... 33

7 Real Applications ...................................................................................................... 35

7.1 A Simple Fan Application ............................................................................................ 35

7.2 A Closed Loop Controller using a Fan ........................................................................ 36

7.3 Controlling Lift Door Operation.................................................................................... 39

7.4 A Conveyor Application using several MICROMASTERs .......................................... 41

7.5 A Material Handling Application .................................................................................. 43

7.6 An Exercise Machine Application................................................................................ 45

8 Advanced Applications Information........................................................................ 47

8.1 Using Closed Loop Control ......................................................................................... 47

8.2 Braking and Slowing down using Inverters ................................................................. 49

8.3 Using the Serial Interface............................................................................................ 51

8.4 Using PROFIBUS........................................................................................................ 52

8.5 Vector and FCC Control.............................................................................................. 53

9 Options for Siemens Standard Drives .................................................................... 57

9.1 Introduction.................................................................................................................. 57

9.2 Advanced Operating Panel AOP................................................................................. 57

9.3 Braking Modules and Braking Resistors .................................................................... 58

9.4 EMC Filters.................................................................................................................. 58

9.5 PROFIBUS Module ..................................................................................................... 58

9.6 Input and Output Chokes ............................................................................................ 58

A Environmental Protection Levels (IP rating) .......................................................... 59

B Some Useful Formulae ............................................................................................. 61

B.1 Torque and Power Relationships ................................................................................ 61

International English Contents

MICROMASTER Applications Handbook vii

List of Figures

Figure 1-1 Induction Motor. Simplified Cross Section ............................................. 1

Figure 1-2 Torque Speed Characteristics of an Induction

Motor ...................................................................................................... 2

Figure 1-3 Torque Reduction above Base Speed.................................................... 3

Figure 1-4 Inverter Block Diagram ........................................................................... 3

Figure 1-5 Pulse Width Modulation.......................................................................... 4

Figure 3-1 Sources of Supply Disturbance .............................................................. 10

Figure 3-2 Rectifier Input Voltages and Currents..................................................... 11

Figure 3-3 Typical Harmonic currents in 230 V single and

three-phase supplies, (750 W Inverter)................................................... 12

Figure 3-4 Operating Capabilities of Motor/Inverter

Combinations.......................................................................................... 13

Figure 3-5 Torque/Speed Characteristics ................................................................ 14

Figure 3-6 Variable Torque/Load Characteristics .................................................... 14

Figure 3-7 Matching the load to the Motor/Inverter

Capabilities............................................................................................. 15

Figure 4-1 Input Wiring. Single-Phase Supplies ..................................................... 18

Figure 4-2 Input Wiring. Three-Phase Supplies ...................................................... 18

Figure 4-3 1AC or 3AC, 230 V Input. (Motor usually Delta

Connected)............................................................................................. 18

Figure 4-4 3AC, 400 – 575 V Input. (Motor usually Star

Connected)............................................................................................. 18

Figure 4-5 Typical Installation .................................................................................. 19

Figure 5-1 Using a Potentiometer with the Analog Input.......................................... 21

Figure 5-2 Using all the Digital Inputs ...................................................................... 22

Figure 5-3 Composite Control Cycle........................................................................ 23

Figure 5-4 Smoothing applied to UP and DOWN ramps.......................................... 25

Figure 5-5 Possible control cycle using brake control relay

and times................................................................................................ 26

Figure 5-6 Slip Compensation ................................................................................. 27

Figure 5-7 Voltage Boost ......................................................................................... 28

Figure 6-1 EMC. Emissions and Immunity.............................................................. 29

Figure 6-2 Star Point Grounding .............................................................................. 31

Figure 6-3 Screening of Control Cables................................................................... 31

Figure 6-4 Separation of Control and Power Connections....................................... 31

Figure 6-5 Suppression of Contactor Coils .............................................................. 32

Figure 6-6 Use of Screened or Armoured Cables.................................................... 32

Contents International English

viii MICROMASTER Applications Handbook

Figure 7-1 Fan Application....................................................................................... 35

Figure 7-2 Extractor System using Closed Loop Flow

Control.................................................................................................... 37

Figure 7-3 Lift Door Operation ................................................................................. 39

Figure 7-4 Conveyor Application............................................................................. 41

Figure 7-5 Material Handling Application ................................................................. 43

Figure 7-6 Exercise Machine ................................................................................... 45

Figure 8-1 A Typical Closed Loop Controller ........................................................... 48

Figure 8-2 Graph showing the Motor acting as a Generator.................................... 49

Figure 8-3 Absorbing Regenerated Current............................................................. 50

Figure 8-4 Braking Methods..................................................................................... 51

Figure 8-5 Vector Diagram. Load Current against Flux

Current.................................................................................................... 53

Figure 8-6 Comparison. DC Motor/AC Motor.......................................................... 54

Figure 8-7 Position Fedback via a Motor Shaft Encoder.......................................... 54

Figure B-1 Practical Assemblies. Gearbox.............................................................. 61

Figure B-2 Practical Assemblies. Conveyor ............................................................ 62

List of Tables

Table 7-1 Fan Application with Manual Control ...................................................... 36

Table 7-2 Fan Application with Closed Loop Control.............................................. 38

Table 7-3 Key Parameters. Lift Door Operation..................................................... 40

Table 7-4 Key Parameters. Conveyor Application ................................................. 42

Table 7-5 Key Parameters. Material Handling Operation ...................................... 44

Table 7-6 Key Parameters. An Exercise Machine

Operation................................................................................................ 46

Table A-1 Protection levels (IP Rating) ................................................................... 59

International English Introduction

MICROMASTER Applications Handbook 1

1 Introduction

This manual is intended to help users of variable speed drives successfully install

and utilize Siemens Standard Drives.

It includes an introduction to drives, which may be informative to first time users.

Detailed technical information and complete parameter descriptions are available

in the Reference Manual and the Parameter List.

INTERNET Address:

http://www.siemens.de/micromaster

These sites will allow access to handbooks, application and training information, as

well as Frequently Asked Questions. (FAQs).

1.1 What is a Variable Speed Drive?

A Variable Speed Drive (VSD) consists of a Motor and some form of controller.

Early electric VSDs consisted of AC and DC motors combinations which were used

as rotating controllers. The first electronic controllers used Thyristor (SCR)

Rectifiers which controlled the voltage, and therefore the speed of DC motors.

These DC VSDs are still widely used and offer very sophisticated control capability.

However, the DC motor is large, expensive and requires periodic brush

maintenance. The AC induction motor is simple, low cost, reliable and widely used

throughout the world.

In order to control the speed of an AC induction motor a more complex controller,

usually called an inverter is required.

In order to understand how an inverter works, it is necessary to understand how an

induction motor works.

An induction motor works like a transformer. When the stator (the fixed, outer

winding) is connected to a three-phase power source, a magnetic field is set up

which rotates at the frequency of the supply.

Figure 1-1 shows a simplified cross-section of an induction motor.

1

2

3

1

2

3

Stator Windings

Air Gap

Rotor

Shaft

Figure 1-1 Induction Motor. Simplified Cross Section

Introduction International English

2 MICROMASTER Applications Handbook

This field crosses the air gap between the stator and rotor and causes currents to

flow in the rotor windings. This produces a force on the rotor as the current

interacts with the changing magnetic field, and the rotor turns.

If the windings are arranged in several pairs (or poles), the frequency of the

rotating field will be less than the applied frequency (e.g. two pole = 50/60 Hz =

3000/3600 rpm, but four pole = 50/60 Hz = 1500/1800 rpm). However, if the rotor

runs at the same speed as the rotating field, there will be no changing

magnetic

field, and therefore no torque. Therefore the rotor always runs a little slower than

the rotating field in order to generate torque. This difference in speed is known as

slip

.

You can see that the speed of the motor depends on the applied frequency, as well

as the winding arrangement, and a little on the load. Therefore in order to control

the motor speed it is necessary to control the frequency of the supply.

If the frequency is reduced, the voltage must be reduced or the magnetic flux will

be too high and the motor will saturate so the voltage must be controlled as well. If

the frequency is increased above normal, more voltage would normally be needed

to maintain maximum flux. Since this is not usually possible, less torque is

available at high speed.

Speed

Normal Operating

Point

Slip

Pull out (Maximum)

Torque

Variable frequency operation

Figure 1-2 Torque Speed Characteristics of an Induction Motor

International English Introduction

MICROMASTER Applications Handbook 3

Torque

Flux, Voltage

Speed ( X 50/60)

Torque

Capability

0 0.5 1.0 1.2 1.5

Figure 1-3 Torque Reduction above Base Speed

Therefore in order to control the speed of a standard AC motor, the applied

frequency and voltage must be controlled.

Although it is difficult to control voltage and frequencies at these high powers, the

use of a standard induction motor allows a cost-effective speed control system to

be built.

1.2 The Variable Frequency Inverter

An electronic converter that converts Direct Current (DC) to Alternating Current

(AC) is known as an inverter. Electronic speed controllers for AC motors usually

convert the AC supply to DC using a rectifier, and then convert it back to a variable

frequency, variable voltage AC supply using an inverter bridge. The connection

between the rectifier and inverter is called the DC link. The block diagram of a

speed controller (often called an inverter) is shown in Figure 1-4.

Motor

Supply

Rectifier DC Link Inverter

+

-

Figure 1-4 Inverter Block Diagram

Introduction International English

4 MICROMASTER Applications Handbook

The supply, which can be single phase (usually at low power) or three-phase is fed

to a full wave rectifier which supplies the DC link capacitors. The capacitors

reduce the voltage ripple (especially on single-phase supplies) and supply energy

for short breaks in the input supply. The voltage on the capacitors is uncontrolled

and depends on the peak AC supply voltage.

The DC voltage is converted back to AC using Pulse Width Modulation (PWM).

The desired waveform is built up by switching the output transistors (Insulated

Gate Bipolar Transistors (IGBTs) on and off at a fixed frequency (the switching

frequency). By varying the on and off time of the IGBTs the desired current can be

generated, but the output voltage is still a series of square wave pulses. Pulse

Width Modulation is shown in Figure 1-5.

0 V

Time

Voltage

Current

Figure 1-5 Pulse Width Modulation

There are many complex aspects of inverters which need to be considered during

the design:

· The control system to calculate the PWM requirements is very complex and

specially designed integrated circuits (ASICs) are needed.

· The control electronics are often connected to the DC link, which is connected

to the supply, so the customer connections, display etc. must be safely isolated

from this.

· The output current must be carefully monitored to protect the inverter and the

motor during overload and short circuit.

· At first switch on the DC link capacitors are discharged, and the inrush current

must be limited, usually using a resistor which is bypassed by a relay after a few

seconds.

· All connections to the inverter, especially the supply and control connections,

may carry a lot of interference and must be fitted with suitable protection

components.

· An internal power supply with several different output voltages is needed to

supply the control electronics.

· The inverter, especially the IGBTs and rectifier diodes, produce heat which

must be dissipated using a fan and heatsink.

International English Introduction

MICROMASTER Applications Handbook 5

· The PWM output voltage contains many high frequency harmonics (because of

the fast switching) and can be a major source of EMI.

· The input rectifier draws current only at the peak of the supply waveform, so the

input currents have a poor form factor ( i.e. the RMS value can be quite high -

this does not mean the inverter is inefficient!).

A practical inverter needs to be designed for ease of use and installation. Large

inverters are often specially designed or engineered for each application; smaller

inverters are designed for general purpose use and are of standard design.

Siemens Standard Drives division manufacture standard inverters for this purpose.

Introduction International English

6 MICROMASTER Applications Handbook

International English Product Range

MICROMASTER Applications Handbook 7

2 Siemens Drives Product Range

The current product range consists of several different product types:

The MICROMASTER Vector (MM440). A VSD high performance inverter for

general purpose applications available in various voltage ranges.

The MICROMASTER (MM420). A similar range with fewer features for simple

applications.

The MICROMASTER Eco. A VSD especially designed for Heating, Ventilating and

Air Conditioning applications.

The COMBIMASTER. An induction motor with an inverter mounted in place of the

terminal box.

Larger and more sophisticated drives for engineered applications can be supplied

by other Siemens drives divisions.

The following information refers to the operation of the MICROMASTER products

in particular, but is applicable to all VSDs.

Product Range International English

8 MICROMASTER Applications Handbook

International English Selecting a Drive

MICROMASTER Applications Handbook 9

3 Selecting a Drive

Often drive selection is straight forward, as a motor is already installed and the

speed range requirement is not excessive. However, when a drive system is

selected from first principles, careful consideration may avoid problems in

installation and operation, and may also save significant cost.

3.1 Overall Considerations

Check the Current rating of the inverter and the motor. Power rating is only a

rough guide.

Check that you have selected the correct operating voltage. 230 V three-phase

input MICROMASTERs will operate with single or three-phase inputs. 400 V

MICROMASTERs are for three-phase application only. Single-phase input units

can be more cost effective in some cases, but note that 230 V units will be

damaged if operated at 400 V. See section 3.2.1.

Check the speed range you require. Operation above normal supply frequency (50

or 60 Hz) is usually only possible at reduced power. Operation at low frequency

and high torque can cause the motor to overheat due to lack of cooling.

Synchronous motors require de-rating, typically by 2-3 times. This is because the

power factor, and hence the current, can be very high at low frequency.

Check overload performance. The inverter will limit current to 150 or 200% of full

current very quickly. A standard, fixed speed motor will tolerate these overloads.

Do you need to stop quickly? If so, consider using a braking resistor to absorb the

energy. A separate braking unit may be required for some VSDs. See section 0,

Do you need to operate with cables longer than 50m, or screened or armored

cables longer than 25m? If so, it may be necessary to de-rate, or fit a choke to

compensate for the cable capacitance.

3.2 Supply Side Requirements

In order to achieve reliable operation, the main power supply to the inverter system

must be suited to the inverter and the anticipated power supplied. The following

points should be considered:

3.2.1 Supply Tolerance

Inverters are usually designed to operate on a wide range of supply voltages. For

example:

Low Voltage units 200 - 240 V ±10% i.e. 180 - 264 V

High Voltage units 380 - 480 V ±10% i.e. 342 - 528 V

Very High Voltage units 500 - 600 V ±10% i.e. 450 - 660 V

Inverters will operate over a wide supply frequency range, typically 47 - 63 Hz

However, many supplies vary outside these voltage levels. For example:

Selecting a Drive International English

10 MICROMASTER Applications Handbook

Supplies at the end of long power lines in remote areas can rise excessively in the

evening and weekends when large loads are no longer present.

Industries with locally controlled and generated supplies can have poor regulation

and control.

Power systems in certain parts of the world may not meet expected tolerances.

In all installations, check that the supply will remain within the tolerances stated

above. Operation outside of the stated supply levels will probably cause damage.

3.2.2 Supply Disturbance

Many supplies are well controlled and remain in tolerance, but are affected by local

disturbances. These can cause faulty operation and damage to inverters. In

particular, check for:

· Power Factor Correction equipment. Unsuppressed switching of capacitor

banks can produce very large voltage transients and is a common cause of

inverter damage.

· High power welding equipment, especially resistance and RF welders.

· Other drives (in particular large, old DC drives), semiconductor heater

controllers etc.

Note.

Inverters are designed to absorb high levels of supply disturbance. Voltage spikes

up to 4 kV for instance. However, the above equipment can cause power supply

disturbances in excess of this. It will be necessary to suppress this interference -

preferably at source - or at least by the installation of an input choke in the inverter

supply. EMC filters do not suppress disturbances with this level of energy; over

voltage protection products such as metal oxide varistors should be considered.

Damage can also be caused by local supply faults and the effects of electrical

storms. In areas where these are expected, similar precautions are recommended.

Figure 3-1 Sources of Supply Disturbance

MICROMASTER

Motor

Power Factor

Correction

Equipment

Welders

RF Heaters etc.

Large Drives and

Power Electronic

Systems

Lightning, Power

System Faults

Add input inductor and

Over Voltage Protection

Equipment here.

International English Selecting a Drive

MICROMASTER Applications Handbook 11

3.2.3 Ungrounded Supplies

Certain industrial installations operate with supplies that are isolated from the

protective earth (IT supply). This permits equipment to continue to run following an

earth fault. However, MICROMASTERs are designed to operate on grounded

supplies and are fitted with interference suppression capacitors between the supply

and ground. Hence operation on ungrounded supplies may be restricted. Some

inverters are designed to allow the removal of these capacitors and enable limited

operation with ungrounded supplies. Please consult Siemens for clarification.

3.2.4 Low Frequency Harmonics

The inverter converts the AC supply to DC using an uncontrolled diode rectifier

bridge. The DC link voltage is close to the peak AC supply voltage, so the diodes

only conduct for a short time at the peak of the AC waveform.

The current waveform therefore has a relatively high RMS value as high current

flows from the supply for a short time.

Input Voltage Input Current DC Link Voltage

Single Phase

Three Phase

Figure 3-2 Rectifier Input Voltages and Currents

This means that the current waveform is consists of a series of low frequency

harmonics, and this may in turn cause voltage harmonic distortion, depending on

the supply impedance.

Sometimes these harmonics need to be assessed in order to ensure that certain

levels are not exceeded. Excessive harmonic levels can cause high losses in

transformers, and may interfere with other equipment. In any case, the rating and

selection of cabling and protection equipment must take these high RMS levels into

account. Some measured harmonic levels are shown In Figure 3-3.

Selecting a Drive International English

12 MICROMASTER Applications Handbook

Figure 3-3 Typical Harmonic currents in 230 V single and three-phase supplies,

(750 W Inverter).

In order to calculate the harmonics in a particular supply system it is essential that

the supply impedance is known. This is usually stated in terms of fault current

levels, transformer size and installed impedance such as line inductors etc.

Computer programs are available to calculate the current and voltage harmonic

levels, dependent on the load, type and number of inverters in the system. In

general, industrial supplies do not require this level of assessment.

Where supplies have very low impedance (such as below 1%) an input inductor is

recommended in any case to limit peak currents in the drive.

3.3 Motor limitations

For more information concerning calculation of Power requirements, Torque, and

Moment of Inertia, see Appendix B.

The motor speed is determined mainly by the applied frequency. The motor slows

down a little as the load increases and the slip increases. If the load is too great

the motor will exceed the maximum torque and stall or ‘pull out’. Most motors and

inverters will operate at 150% load for a short time, (60 seconds for instance).

The motor is usually cooled by a built in fan that runs at motor speed. This is

designed to cool the motor at full load and base speed. If a motor runs at a lower

frequency and full torque - that is high current - cooling may be inadequate. Motor

manufacturers will give the necessary de-rating information, but a typical derating

curve would limit output torque to 75% at zero frequency rising to full capability at

50% of base speed. See Figure 3-4. Ensure that these limitations are not

exceeded for long term operation.

Consider using the I

2

t function to help protect the motor ( see section 5.7.1) or

consider using a motor with built in protection such as a PTC.

0

1

2

3

4

5

6

7

Fundamental

3rd

5th

7th

9th

11

th

13

t

h

15

t

h

1ph 750W

3ph 750W

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Siemens Microscope & Magnifier A1 User manual

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