Soft starters for AC motors offer many benefits, with the most significant being a reduction of mechanical stresses on the motor and shaft as well as other components in a system, thereby extending equipment life. They also contribute to smarter use of power and less inrush current, which can minimize penalties from utility companies. An industry expert from Eaton explains these and other benefits of soft starters as well as some of the advantages of soft starters over traditional motor starters. Viewers will also learn about: • How to monitor and protect your equipment and reduce overall system costs • How to select soft starters for unique applications • Reducing or eliminating water hammer effect and check valve slamming • Considerations for heavy-duty applications Further, specific attention will be given how to select soft start controllers for unique application requirements.

1. Advantages of Soft
Start Motor Control
© 2011 Eaton Corporation. All rights reserved.
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2. Before We Start
 This webinar will be available afterwards at
designworldonline.com & email
 Q&A at the end of the presentation
 Hashtag for this webinar: #DWwebinar
© 2011 Eaton Corporation. All rights reserved.
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3. Moderator
Presenter
Miles Budimir
Ram Tenneti
Senior Editor
Product Manager
Design World
Eaton
Design World
Design World
© 2011 Eaton Corporation. All rights reserved.
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4. This is a photographic template – your
photograph should fit precisely within this rectangle.
Advantages of Soft Start Motor Control
Hosted by Ram Tenneti
Product Manager, Eaton Corporation
© 2011 Eaton Corporation. All rights reserved.

5. Agenda
• What is a soft starter?
• Reduced voltage starting
mechanisms
• Inner workings of a soft starter
• Soft starters for pumping
applications
• Soft starters in severe duty applications
• The value of soft starters
• Specification for various application
requirements
© 2011 Eaton Corporation. All rights reserved.
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6. What is a soft starter?
• A soft starter is a solid-state
device used with AC electric
motors to ramp up the voltage
and torque on the motor during
startup
• This ramp up reduces mechanical
stress on the motor and shaft, as
well as the electro-dynamic stresses
on the attached power cables and
electrical distribution network
• The bottom line: soft starters extend the lifespan of
your system and reduce maintenance costs
© 2011 Eaton Corporation. All rights reserved.
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7. Traditional reduced voltage starter types
• Auto transformer
• Part winding
• Wye-Delta
© 2011 Eaton Corporation. All rights reserved.
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8. Auto transformer starter
• On start-up, line voltages
are directed through
transformers, which
reduce the voltage
• After an adjustable time,
the transformers are
removed from the circuit
• Allow for simple closed
transition from start to run
• Minimal reduction in
starting torque
© 2011 Eaton Corporation. All rights reserved.
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9. Part winding starter
• Constructed of two separate
parallel stator windings per
phase
• One winding set energized on
start, all windings energized
during run
• Time delay relay closes the
additional run windings
• Start windings draw 65% to
85% of the motor locked rotor
current
• Each winding set carries 50%
of load during run
© 2011 Eaton Corporation. All rights reserved.
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10. Wye-Delta starter configuration
© 2011 Eaton Corporation. All rights reserved.
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11. Wye-Delta starter connected in Wye
• Wye connection for START
• Typically use in applications
with high inertia and long
acceleration periods (large
centrifugal pumps, fans)
• All stator windings are used
during start-up
• Less current draw at start-up
© 2011 Eaton Corporation. All rights reserved.
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12. Wye-Delta starter connected in Delta
• Delta Connection for RUN
• Close transition when
transferring between Wye
and Delta requires inline
resistors during transition
(direct closed transitioning
will cause a high inrush)
• Open transition is most
common
• Full current draw
© 2011 Eaton Corporation. All rights reserved.
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13. What is a soft starter, again?
• Soft starter is a solid state device used with
AC electric motors to ramp up the voltage and
torque on the motor during startup
• This ramp up reduces mechanical stress on
the motor and shaft, as well as the electrodynamic stresses on the attached power
cables and electrical distribution network, thus
extending the lifespan of the system
© 2011 Eaton Corporation. All rights reserved.
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14. Solid-state starters
• Electronically reduce the voltage output to the
motor
• Typically silicone controlled rectifiers (SCR) are
used to reduce the voltage
• Allows for greater control flexibility
© 2011 Eaton Corporation. All rights reserved.
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15. Soft starter schematic diagram
© 2011 Eaton Corporation. All rights reserved.
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16. Voltage ramp soft start
•
Smooth transition from
initial voltage to full voltage
© 2011 Eaton Corporation. All rights reserved.
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17. Inrush current comparison (300HP)
© 2011 Eaton Corporation. All rights reserved.
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18. Why upgrade to soft starters?
• Soft starter lowers inrush current compared to acrossthe-line and WYE-DELTA starting methods
• Reduces stress on components (belts, chains,
conveyors)
• Reduces long-term maintenance costs
• Increases system uptime
• In pump applications, reduces water hammer effect by
utilizing pump control algorithm
• Reduces heat build up in enclosure because of
internal by-pass
• Reduces peak inrush current resulting in minimizing
penalty from the utility companies
© 2011 Eaton Corporation. All rights reserved.
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19. Pump application challenges
• High in-rush currents
• Squirling and snapping belts
• Water-hammer
© 2011 Eaton Corporation. All rights reserved.
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20. Understanding water hammer effect
• Pressure surge caused by
abrupt changes in the rate of
flow because of pump starts
and stops, opening/closing of
valves or water column
separation and closure
• The abrupt changes can cause
all or part of the flowing water
column to undergo a
momentum change
• This change in momentum
causes a shock wave that
damages the system
© 2011 Eaton Corporation. All rights reserved.
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21. Starting flow characteristics
© 2011 Eaton Corporation. All rights reserved.
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22. Stopping flow characteristics
© 2011 Eaton Corporation. All rights reserved.
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23. Soft starters for pump applications
• Eliminates water hammer and check valve slam in
hydraulic systems
• Extended stopping time
• S-shaped torque curve to ramp up and ramp down the
flow
© 2011 Eaton Corporation. All rights reserved.
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24. See the difference, watch the video
• Eaton developed a short, 30-second video clip
that shows the advantage of a soft starter in a
pumping application
© 2011 Eaton Corporation. All rights reserved.
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25. Heavy duty applications – reduced voltage soft start
• RVSS used to improve Wye/Delta Start Characteristics
• Centrifuge:
• 10 minutes or more with Wye/Delta systems.
• 4 - 5 minutes with RVSS.
• RVSS more tolerant of starts attempted with remaining process
in the centrifuge (Additional mass = longer acceleration time).
• RVSS provides full motor protection during start-run operations.
• Peak current ≈ 3.5 FLA, no spikes during contactor movement as
with Wye-Delta systems.
• Aggregate/Conveyor – Kick Start
• Kick start to overcome friction
• Switch over to soft starter mode after couple of seconds
© 2011 Eaton Corporation. All rights reserved.
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26. Success stories
• Location: Pit mine
• Issue: Constant waterhammer effect experienced check valve slam as soon
as the pump turned off
• Challenge: A 285 HP pump
discharging to very long piping
system
• Solution: Special softstarter with pump
algorithm to reduce waterhammer effect
was installed
• Results:
• Reduced downtime
• Extended pump and asset life
© 2011 Eaton Corporation. All rights reserved.
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27. Protection features in soft starters
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•
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•
Phase sequence
Phase rev fault
Motor rated volt
Low volt trip
Low volt level
Low volt trip Dly
Hi volt trip
Hi volt level
Hi volt trip Dly
Jam fault
Stall fault
Temp sense fault
•
•
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•
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•
•
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•
•
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V imbal trip Dly
V imbal trip Lev
Phase loss fault
Phase loss % trip
Phase loss trip Dly
Low I trip % FLA
Phase Imb fault
I Imbal trip lev
I Imbal trip Dly
SCR short fault
Ground Fault
© 2011 Eaton Corporation. All rights reserved.
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28. Full voltage retrofits
• Soft starters typically fit in any MCC/enclosure
installation you have today
• Box replacement not needed
• Built-in shorting (bypass) contactor minimizes
wiring
• Reuse all the same components you have today
• Quick installation saves electrician s time and
down time
© 2011 Eaton Corporation. All rights reserved.
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29. Soft starter solutions for various
applications
Low Voltage Soft Starters
Up to 1000Amps
Up to 690 volts
Up to 800HP
S811
S801
S611
DS6
30 - 800 HP
0 to 690 V
DS7
Up to 350 HP
0 to 600 V
Up to 25 HP
0 to 480 V
1Q 2011
30 - 800 HP
0 to 690 V
Up to 150 HP
0 to 480 V
© 2011 Eaton Corporation. All rights reserved.
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30. Soft starters for industrial applications
Key considerations
 Smaller in Size
 Built-in run bypass contactor
 Built-in overload protection
 Adjustable ramp times
 Adjustable kick start control
 Physically fits in place of most
NEMA and IEC starters
 Digital Interface
 Pump control
 Communication Capability
© 2011 Eaton Corporation. All rights reserved.
Product Range
 Amps: 37 – 1000A
 Voltage: Up to 690V
 Power: 25 – 800HP
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31. Soft starters for commercial applications
Key considerations
 Integrated bypass
 Integrated electronic overload
protection
 120V control
 Power monitoring
 Intuitive user interface
 Serviceability (control board,
contactors)
 Pump control option
 ModBus Native
 Plug and Play adapters for Profibus/
Devicenet/Ethernet IP
 Available in NEMA 1/12/3R/4/4X
enclosures
Product Range
 Current: 52 to 414A
 Voltage: Up to 600V
 Power: 40 to 350HP
© 2011 Eaton Corporation. All rights reserved.
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32. Key soft start specifications
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•
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Compact size
Integrated by-pass contactor
Electronic overload protection
Increased capacity of product when used in
inside the delta mode
• Feature-rich products with extensive
monitoring and protective features
• Pump algorithm to minimize/eliminate water
hammer effect
© 2011 Eaton Corporation. All rights reserved.
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33. For more information
• Multiple tools are available
on Eaton s website including
application notes, podcasts, FAQs,
quick start guide, manuals,
catalogs etc.
• Visit Eaton s soft starter
product page at:
www.eaton.com/softstarters
© 2011 Eaton Corporation. All rights reserved.
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34. Questions?
Design World
Eaton Corp.
Miles Budimir
Ram Tenneti
Email: mbudimir@wtwhmedia.com
Email: RamTenneti@eaton.com
Phone: 440.234.4531
Phone: 734.730.9513
Twitter: @DW_Motion
© 2011 Eaton Corporation. All rights reserved.
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35. Thank You
 This webinar will be available at
designworldonline.com & email
 Tweet with hashtag #
 Connect with
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 Discuss this on EngineeringExchange.com
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36. © 2011 Eaton Corporation. All rights reserved.
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