ABB Softstarters User Manual
SOFTSTARTER
HANDBOOK
FOREWORD
This book is written with the thought of being a general guide for people working with
softstarter applications but also for those just interested in learning more about this type
of starting method. It doesn’t matter if you are an expert or novice, hopefully you will find
some interesting and useful information either by reading from cover to cover or just the
chapters of interest.
The index at the end of the book can be used to simplify your search.
The content of this book is very much based on the 20 years of experience we have within
ABB of developing, manufacturing and selling low voltage softstarters.
The book is not a complete technical guide or manual for all type of ABB Softstarters that
may exist on the market. It is a complement to the technical catalogues and brochures we
have for our products and will give a general picture of what to think about when working
with softstarters.
More information about softstarters as well as other ABB products is available on www.abb.com
All advice given in this book is only general and every single application must be handled
as a specific case.
ABB Automation Technology Products AB, Control
February 2003
Magnus Kjellberg Sören Kling
ABB will not take any responsibility for any type of faults or damage due to the use of this
handbook.
Contents
Standards ...1
European Directives ...1
CE Marking ...1
Specification in USA and Canada ...1
Used standards ...1
General about motors ...2
Squirrel cage motors ...3
Voltage ...4
Power factor ...5
Speed ...6
Torque ...7
Slip-ring motors ...7
Different starting methods ...8
Direct-on-line start (D.O.L) ...9
Star-delta start ...10
Frequency converter ...12
Softstarter ...13
Common problem when starting and stopping motors ...14
Different applications ...15
Centrifugal fan ...16
Direct-on-line start (D.O.L) ...16
Star-delta start ...17
Softstarter ...17
Selection of a suitable Softstarter ...18
Contents
I
Centrifugal pump ...19
Direct-on-line start (D.O.L) ...19
Star-delta start ...20
Softstarter ...21
Selection of a suitable Softstarter ...22
Compressor ...23
Direct-on-line start (D.O.L) ...23
Star-delta start ...24
Softstarter ...25
Contents
Selection of a suitable Softstarter ...26
Conveyor belt ...27
Direct-on-line start (D.O.L) ...27
Star-delta start ...28
Softstarter ...29
Selection of a suitable Softstarter ...30
How to select a softstarter ...31
Description of the softstarters ...33
Description of different components ...34
Common settings ...36
II
Start ramp ...36
Stop ramp ...36
Initial voltage ...36
Current limit ...37
Step down voltage ...38
Adjustable rated motor current ...38
Different indications ...39
Different voltage names ...40
Ambient temperature ...41
High altitudes ...42
Start of several motors ...43
Parallel start of motors ...43
Sequential start of motors ...44
Different ways of connecting the softstarter ...45
In-Line connection ...46
Inside Delta connection ...46
Location of the main contactor ...47
Basic settings ...49
Table for settings without current limit function ...50
Table for settings with current limit function ...51
Starting capacity and overload protection ...52
Starting capacity for softstarters ...52
Starting capacity when using by-pass contactor ...53
Starting capacity when using overload protection ...53
Number of starts/hour ...54
Intermittance factor ...54
Contents
Harmonics ...55
Harmonic content ...55
Explosive atmospheres (EEx) ...56
Hazardous areas and zones ...57
Location and selection of softstarter ...57
Co-ordination ...58
Types of co-ordination ...59
Utilization Categories ...60
Types of fuses ...61
Where to find the co-ordination tables ...62
How to read the co-ordination tables ...63
ESD aspects ...65
Two type of faults and different circuits ...65
Electro static voltage levels ...66
Protection against ESD damages ...66
III
Frequently Asked Questions (FAQ) ...67
Environmental information ...69
LCA ...69
Contents
EPD ...70
Industrial IT ...71
Different levels ...72
Softstarter level ...72
Formulas and conversion factors ...73
Formulas ...73
Quantities and units ...75
Conversion factors ...76
Glossary ...78
IV
Index ...84
Standards
All ABB low voltage softstarters are developed and manufactured according to the rules
set out in the IEC (International Electrotechnical Commission) which is a part of the
International Standard Organisation, ISO.
ISO issue IEC publications that act as a basis for the world market.
Softstarters built according to these standards are in most countries not subject to
any other tests besides the manufacturer responsibility. In some countries, law requires
certificates.
For softstarters used on board ships, maritime insurance companies sometimes require
certificates of approval from BV (Bureau Veritas), GL (Germanisher Lloyd) and LRS
(Lloyd’s Register of Shipping) or other independent certification organisation.
European Directives
There are three essential European directives:
Low Voltage Directive 73/23/EEC
Concerns electrical equipment from 50 to
1000 V AC and from 75 to 1500 V DC.
Machines Directive 89/392/EEC
Concerns safety specifications of machines
and equipment on complete machines.
Electromagnetic Compatibility Directive
89/336/EEC
Concerns all devices able to create electro-
magnetic disturbance including the level of
emission and immunity.
CE Marking
When a product is verified according to its
applicable IEC standard (IEC 947-4-2 for
softstarters) the product will then fulfil both the
”Lown Voltage Directive” and ”Electromagnetic
Compability Directive” and it is allowed to use
the CE marking on the product. In this case
the CE marking does not cover the ”Machines
Directive” concerning the connection of the
softstarter for a safe run of the motor.
The CE marking is not a quality label; it is proof
of conformity with the European Directives
concerning the product.
Specifications in USA and
Canada
The specifications for the American and
Canadian markets are quite equal but differ a
lot from the IEC standards and other European
specifications.
USA UL Underwriters Laboratories
File ref. 072301-E161428
110800-E161428
Canada CSA Canadian Standards
File ref. 1031179
Used standards
Following standards are used or partly used for
the softstarters.
IEC 60947-1
IEC 60947-1/A11
IEC 60947-4-2, Amd 1
EN 50082-2
UL 508
CSA C22.2 No. 14 - M91
LRS 00/00154
Standards
1
About Motors
Modern electrical motors are available in many different forms, such as single phase
motors, three-phase motors, brake motors, synchronous motors, asynchronous motors,
special customised motors, two speed motors, three speed motors, and so on, all with
their own performance and characteristics.
For each type of motor there are many different mounting arrangements, for example
foot mounting, flange mounting or combined foot and flange mounting. The cooling
method can also differ very much, from the simplest motor with free self-circulation of
About Motors
air to a more complex motor with totally enclosed air-water cooling with an interchangeable
cassette type of cooler.
To ensure a long lifetime for the motor it is important to keep it with the correct
degree of protection when under heavy-duty conditions in a servere environment.
The two letters IP (International Protection) state the degree of protection followed
by two digits, the first of which indicates the degree of protection against contact
and penetration of solid objects, whereas the second states the motor’s degree of
protection against water.
The end of the motor is defined in the IEC-standard as follows:
• The D-end is normally the drive end of the motor.
2
• The N-end is normally the non-drive end of the motor.
Note that in this handbook we will focus on asynchronous motors only.
Drive shaft
Stator windings
Terminal box
Cooling fan
N-endD-end
Stator
Rotor
Squirrel cage motors
In this book the focus has been placed on the
squirrel cage motor, the most common type of
motor on the market. It is relatively cheap and
the maintenance cost is normally low. There are
many different manufacturers represented on the
market, selling at various prices. Not all motors
have the same performance and quality as for
example motors from ABB. High efficiency
enables significant savings in energy costs during
the motor’s normal endurance. The low level of
noise is something else that is of interest today,
as is the ability to withstand severe environments.
There are also other parameters that differ.
The design of the rotor affects the starting current
and torque and the variation can be really large
between different manufacturers for the same
power rating. When using a softstarter it is
good if the motor has a high starting torque at
Direct-on-line (D.O.L) start. When these motors
are used together with a softstarter it is possible to
reduce the starting current further when compared
to motors with low starting torque. The number
of poles also affects the technical data. A motor
with two poles often has a lower starting torque
than motors with four or more poles.
About Motors
3
I
Current diagram for typical sqirrel cage motor
Max. starting current
Rated current
rpm
T
Starting torque
Torque diagram for a typical squirrel cage motor
Max. torque
Rated torque
rpm
Voltage
Three-phase single speed motors can normally
be connected for two different voltage levels.
The three stator windings are connected in star
(Y) or delta (D).
The windings can also be connected in series or
About Motors
parallel, Y or YY for instance. If the rating plate
on a squirrel cage motor indicates voltages for
both the star and delta connection, it is possible
to use the motor for both 230 V, and 400 V as an
example.
The winding is delta connected at 230 V and if
the main voltage is 400 V, the Y-connection is
used.
When changing the main voltage it is important
to remember that for the same power rating the
rated motor current will change depending on the
voltage level.
The method for connecting the motor to the
terminal blocks for star or delta connection is
shown in the picture below.
W2
4
W1
L3
V2 V1
– Connection
230 V
(400 V)
Wiring diagram for Y- and Delta connection
L1
W1U1 V1
U1
L1
U1
U2
W2
V2
V1
L2
V2W2 U2
U2
L2
L3
W1
V2W2 U2
W1U1 V1
L3L1 L2
L3L1 L2
Y – Connection
400 V
(690 V)
Power factor
A motor always consumes active power, which it
converts into mechanical action. Reactive power
is also required for the magnetisation of the motor
but it doesn’t perform any action. In the diagram
below the active and reactive power is represented
by P and Q, which together give the power S.
The ratio between the active power (kW) and the
reactive power (kVA) is known as the power
factor, and is often designated as the cos ϕ. A
normal value is between 0.7 and 0.9, when
running where the lower value is for small motors
and the higher for large ones.
About Motors
P
ϕ
Q
Diagram indicating P, Q, S and Cos ϕ
S
5
Speed
The speed of an AC motor depends on two things:
the number of poles of the stator winding and
the main frequency. At 50 Hz, a motor will run
at a speed related to a constant of 6000 divided
by the number of poles and for a 60 Hz motor
the constant is 7200 rpm.
About Motors
To calculate the speed of a motor, the following
formula can be used:
2 x f x 60
n =
p
n = speed
f = net frequency
p = number of poles
Example:
4-pole motor running at 50 Hz
2 x 50 x 60
n =
6
This speed is the synchronous speed and a
squirrel-cage or a slip-ring motor can never
reach it. At unloaded condition the speed will
be very close to synchronous speed and will
then drop when the motor is loaded.
4
= 1500 rpm
The difference between the synchronous and
asynchronous speed also named rated speed is
”the slip” and it is possible to calculate this by
using the following formula:
n1 - n
s =
n
1
s = slip (a normal value is between 1 and 3 %)
n1 = synchronous speed
n = asynchronous speed (rated speed)
Table for synchronous speed at different
number of poles and frequency:
No. of poles 50 Hz 60 Hz
2 3000 3600
4 1500 1800
6 1000 1200
8 750 900
10 600 720
12 500 600
16 375 450
20 300 360
T
Diagram showing syncronous speed vs.rated speed
Rated speed
Syncronous
speed
}
rpm
Slip
Torque
The starting torque for a motor differs significantly
depending on the size of the motor. A small
motor, e.g. ≤ 30 kW, normally has a value of
between 2.5 and 3 times the rated torque, and
for a medium size motor, say up to 250 kW, a
typical value is between 2 to 2.5 times the rated
torque. Really big motors have a tendency to have
a very low starting torque, sometimes even lower
than the rated torque. It is not possible to start
such a motor fully loaded not even at D.O.L
start.
The rated torque of a motor can be calculated
using the following formula:
9550 x P
=
M
r
Mr = Rated torque (Nm)
Pr = Rated motor power (kW)
nr = Rated motor speed (rpm)
r
n
r
Slip-ring motors
In some cases when a D.O.L start is not permitted
due to the high starting current, or when starting
with a star-delta starter will give too low starting
torque, a slip-ring motor is used. The motor is
started by changing the rotor resistance and when
speeding up the resistance is gradually removed
until the rated speed is achieved and the motor
is working at the equivalent rate of a standard
squirrel-cage motor.
The advantage of a slip-ring motor is that the
starting current will be lower and it is possible to
adjust the starting torque up to the maximum
torque.
In general, if a softstarter is going to be used for
this application you also need to replace the motor.
T
About Motors
7
T
Tst/Tn1.5...2.5
Torque diagram for a typical squirrel cage motor
rpm
rpm
Torque diagram for a slip-ring motor
I
T
n
rpm
Current diagram for a slip-ring motor
Different starting methods
The following is a short description of the most common starting methods for
squirrel cage motors.
An overview of common problems when starting and stopping a motor with different
starting methods, see page 14
Direct-on-line start (D.O.L)
Different starting methods
8
Start-delta start
Frequency converter
Softstarter
Direct-on-line start (D.O.L)
This is by far the most common starting method
available on the market. The starting equipment
consists of only a main contactor and thermal or
electronic overload relay. The disadvantage with
this method is that it gives the highest possible
starting current. A normal value is between 6 to 7
times the rated motor current but values of up to
9 or 10 times the rated current exist. Besides the
starting current there also exists a current peak
that can rise up to 14 times the rated current
since the motor is not energised from the the first
moment when starting.
The values are dependent on the design and size
of the motor, but in general, a smaller motor
gives higher values than a larger one.
During a direct-on-line start, the starting torque
is also very high, and is higher than necessary for
most applications. The torque is the same as the
force, and an unnecessary high force gives
unnecessary high stresses on couplings and the
driven application. Naturally, there are cases
where this starting method works perfectly and
in some cases also the only starting method that
works.
Different starting methods
D.O.L. starter with contactor
and O/L relay
KM 1 Main contactor
FR 1 Overload relay
KM 1
FR 1
M
Single line diagram
for a D.O.L.
T
Starting torque
Torque/speed curve att D.O.L start
I
Current curve at D.O.L start
Max. starting current
Max. torque
9
Rated torque
rpm
Rated current
rpm
Star-delta start
This is a starting method that reduces the starting
current and starting torque. The device normally
consists of three contactors, an overload relay and
a timer for setting the time in the star-position
(starting position). The motor must be delta
connected during a normal run, in order to be
able to use this starting method.
The received starting current is about 30 % of
the starting current during direct on line start and
the starting torque is reduced to about 25 % of
the torque available at a D.O.L start. This starting
method only works when the application is light
Different starting methods
loaded during the start. If the motor is too heavily
loaded, there will not be enough torque to
10
accelerate the motor up to speed before switching
over to the delta position.
When starting up pumps and fans for example,
the load torque is low at the beginning of the
start and increases with the square of the speed.
When reaching approx. 80-85 % of the motor
rated speed the load torque is equal to the motor
torque and the acceleration ceases. To reach the
rated speed, a switch over to delta position is
necessary, and this will very often result in high
transmission and current peaks. In some cases the
current peak can reach a value that is even bigger
than for a D.O.L start. Applications with a load
torque higher than 50 % of the motor rated torque
will not be able to start using the start-delta starter.
KM 2
KM 3 KM 1
400 V
Different starting methods
230 V
KM 1 Main contactor
KM 2 Delta contactor
KM 3 Star contactor
FR 1 Overload relay
T
FR 1
FR 1
I
KM 1
KM 3KM 2
M
Single line diagram for a Star-delta starterStar-delta starter with contactors and O/L relay
11
rpm
Torque/speed curve at Star-Delta start Current curve at Star-Delta start
rpm
Frequency converter
The frequency converter is sometimes also
called VSD (Variable Speed Drive), VFD
(Variable Frequency Drive) or simply Drives,
which is probably the most common name.
The drive consists primarily of two parts, one
which converts AC (50 or 60 Hz) to DC and the
second part which converts the DC back to AC,
but now with a variable frequency of 0-250 Hz.
As the speed of the motor depends on the
frequency this makes it possible to control the speed
of the motor by changing the output frequency
from the drive and this is a big advantage if there
Different starting methods
is a need for speed regulation during a continuous
run.
In many applications a drive is still only used
for starting and stopping the motor, despite the
12
fact that there is no need for speed regulation
during a normal run. Of course this will create a
need for much more expensive starting equipment
than necessary.
By controlling the frequency, the rated motor
torque is available at a low speed and the starting
current is low, between 1 and 1.5 times the rated
motor current. Another available feature is softstop,
which is very useful, for example when stopping
pumps where the problem is water hammering
in the pipe systems at direct stop. The softstop
function is also useful when stopping conveyor
belts from transporting fragile material that can
be damaged when the belts stop too quickly.
It is very common to install a filter together with
the drive in order to reduce the levels of emission
and harmonics generated.
KM 1 Main contactor
Q 1 Frequency converter
AC
DC
Q 1
DC
AC
Frequency converter
KM 1
M
Single line diagram for a frequency converter
Softstarter
A softstarter has different characteristics to the
other starting methods. It has thyristors in the
main circuit, and the motor voltage is regulated
with a printed circuit board. The softstarter makes
use of the fact that when the motor voltage is low
during start, the starting current and starting
torque is also low.
During the first part of the start the voltage to
the motor is so low that it is only able to adjust
the play between the gear wheels or stretching
driving belts or chains etc. In other words,
eliminating unnecessary jerks during the start.
Gradually, the voltage and the torque increase
so that the machinery starts to accelerate.
One of the benefits with this starting method is
the possibility to adjust the torque to the exact
need, whether the application is loaded or not. In
principle the full starting torque is available, but
with the big difference that the starting procedure
is much more forgiving to the driven machinery,
with lower maintenance costs as a result.
Another feature of the softstarter is the softstop
function, which is very useful when stopping
pumps where the problem is water hammering
in the pipe system at direct stop as for star-delta
starter and direct-on-line starter.
The softstop function can also be used when
stopping conveyor belts to prevent material
from damage when the belts stop too quickly.
Different starting methods
13
Softstarter
KM 1
FR 1
Q 1
KM 1 Main contactor
FR 1 Overload relay
Q 1 Softstarter
M
Single line diagram for a softstarter
Common problems when starting and stopping motors with
different starting methods
Type of problem Type of starting method
Direct-on-line Star-delta start Drives Softstarter
Slipping belts and Yes Medium No No
heavy wear on bearings
High inrush current Yes No No No
Heavy wear and tear Yes Yes No No
Different starting methods
on gear boxes (loaded start)
Damaged goods / Yes Yes No No
products during stop
14
Water hammering in pipe Yes Yes Best Reduced
system when stopping solution
Transmission peaks Yes Yes No No
Auto transformer start and start of a part winding motor have similar problems to the star-delta start.
Different applications
All motors are used for starting and running different applications. This chapter
covers the most common ones. The different applications will also result in different
load conditions for the motor. There are two factors to consider:
1. Braking load torque, a direct braking force on the motor shaft. To be able to
accelerate, the motor has to be stronger than the load. The accelerating torque
is the difference between the available motor torque and the load toque.
Accelerating torque = Available motor torque – load torque
2. Involved moment of inertia or flywheel mass will also affect the start.
The bigger inertia the longer starting time for the same motor.
T
Available
motor torque
Accelerating
torque
Braking load
(load torque)
rpm
Centrifugal fan
Centrifugal pump
Compressor
Conveyor belt
Different applications
15
Centrifugal fan
For some applications the motor is started with reduced load torque, i.e. unloaded
start. Big centrifugal fans are often started with a closed damper and this will make
the start easier (shorter) but since the moment of inertia is still present the starting
time might be quite long anyway.
Direct-on-line start
Centrifugal fans are very often driven by one or
more drive belts. During a D.O.L start these belts
have a tendency to slip. The reason is that these
Different applications
types of fans always have a more or less high
moment of inertia (big flywheel). So even if the
fan is started unloaded, the flywheel is still there.
1616
T
rpm
Torque/speed curve at D.O.L start Current curve at D.O.L start
The belts slip depending on whether the starting
torque from the motor is too high during the
start sequence and the belts are not able to
transfer these forces. This typical problem gives
high maintenance costs but also production
losses when you need to stop production to
change belts and bearings.
I
rpm
Star-delta starter (Y-D)
The star-delta starter gives lower starting torque
but depending on the fact that the load torque
increases with the square of the speed, the motor
torque will not be high enough in the star position
to accelerate the fan to the rated speed.
When switching over to delta position it will
be both a high transmission and current peak,
often equal to values when making a D.O.L start
or even higher, with a slipping belt as a result.
It is possible to reduce the slip by stretching the
belts very hard. This gives high mechanical
stresses on bearings both in the motor and the
fan with high maintenance costs as result.
Softstarter
Different applications
The key to solve these problems is to reduce the
starting torque from the motor during start.
By using an ABB softstarter the voltage is
decreased to a low value at the beginning of the
start, low enough to avoid slip but high enough
to start up the fan. The softstarter provides the
ability to adjust to fit any starting condition, both
unloaded and fully loaded starts.
T
Torque/speed curve at Star-Delta start
I
Current curve at Star-Delta start
rpm
rpm
T
17
rpm
Torque/speed curve when using a softstarter
I
rpm
Current curve when using a softstarter
Selection of a suitable
softstarter
Normal start
For fans with small or medium large flywheels,
select a softstarter according to the rated motor
power.
The above is valid if the time for D.O.L start
is less than 5 seconds.
Heavy duty start
For fans with large flywheels, select a softstarter
Different applications
designed for heavy duty start according to the
rated motor power. It is also possible to select a
softstarter for normal start, select a unit with one
size bigger power rating than the motor and use
an overload relay class 30.
The above is valid if the time for D.O.L start
is more than 5 seconds.
1818
Recommended basic settings:
Start ramp: 10 sec.
Stop ramp: 0 sec.
Initial voltage: 30 %
Current limit is recommended for use.
Application with a centrifugal fan
Centrifugal pump
There are a lot of different types of pumps; like piston pumps, centrifugal pumps,
screw pumps etc. But the most common version is the centrifugal pump and we
have selected this one to describe.
Direct-on-line start
Starting up a pump is normally not a problem
for a squirrel cage motor. The problem is the
wear and tear depending on pressure waves in
the pipe system created when the motor starts
and stops too quickly. During a D.O.L start the
motor gives much too high starting torque
with the result that the motor accelerates and
reaches nominal speed too quickly. The reason
is that the braking load torque is low for a pump
during start. This starting method also gives
maximum possible starting current.
T
I
Different applications
19
Torque/speed curve at D.O.L start
rpm
rpm
Current curve at D.O.L start
Star-delta starter (Y-D)
When stopping a pump
By using a star-delta starter it is possible to
reduce the starting torque. The motor torque
in the star position is too weak to be able to
complete the start and reach the rated speed.
The quadratic load torque will become too high
for the motor when reaching approx. 80-85 % of
the rated speed and the switch over to the delta
position will give both high transmission and
current peaks with pressure waves as a result.
Different applications
The current peaks can be equally high as at a
D.O.L start or even higher.
T
During stop it is also normal to have problems.
When making a direct stop by disconnecting
the main supply the motor stops too quickly.
Depending on high mass flow in the pipe system
the water will continue with the same speed for
a short period and then come back again,
backwards in the pipe system. This creates high
pressure shocks on valves and gives high
mechanical stresses on the pipe system.
I
2020
rpm
Torque/speed curve at Star-Delta start Current curve at Star-Delta start
rpm
Softstarter
By using an ABB softstarter the voltage is reduced
during the start sequence with the result that the
motor torque is reduced. During the start
sequence the softstarter increases the voltage so
that the motor will be strong enough to accelerate
the pump to the nominal speed without any
torque or current peaks. A normal starting
current with a softstarter when starting a fully
loaded centrifugal pump is approx. 4 times rated
motor current.
Also during the stop sequence the softstarter is
the solution. The softstarter reduces the voltage
during stop via a voltage ramp and the motor
becomes weaker and weaker. Because of this the
water speed slows down very smoothly without
creating any pressure waves.
A special function on the softstarter is sometimes
available, called "step-down voltage",which ensures
an optimum setting to the actual need for any
pipe system.
Different applications
T
rpm
Torque/speed curve when using a softstarter Current curve when using a softstarter
I
21
rpm
Selection of a suitable
softstarter
Normal start
Starting a pump is a typical normal start
condition.
Select a softstarter according to the rated
motor power.
Heavy duty start
Not applicable for this application.
Different applications
2222
Recommended basic settings:
Start ramp: 10 sec.
Stop ramp: 20 sec.
Initial voltage: 30 %
Application with a pump.
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