Low Voltage Variable Frequency Drive (VFD)
and Related Operation/Protection Issues
Eaton EESS APAC
JJ Dai, PhD, PE
November 2013
IIEE of the Philippines
38th Annual Convention
© 2013 Eaton. All rights reserved.
November 2013
Presentation Topics
• EESS China Organization and Businesses
• VFD Principles and Selections
• VFD and Harmonic Issues
• Harmonic Reduction Methods
• Drive Low Voltage Ride Through Support
• Computer Modeling and Analysis to Electrical
Systems
IIEE of the Philippines
38th Annual Convention
© 2013 Eaton. All rights reserved.
November 2013
EESS China Organization and
Businesses
IIEE of the Philippines
38th Annual Convention
© 2013 Eaton. All rights reserved.
November 2013
EESS APAC Footprint
Mongolia
EESS India
- Field Services
- Power Systems Engineering
- Aftermarket Life Extension /
Retrofits / Modernization
- Turnkey Project / Project
Management
Korea Rep
China
Pakistan
Japan
Nepal Bhutan
India
Bangladesh
Myanmar
Hong Kong
Laos Macau
Taiwan
Vietnam
Thailand
Philippines
Malaysia
Sri Lanka
Brunei
Singapore
EESS China
- Field Services
- Power Systems Engineering
- Power System Automation
- PowerChain Solution
- Application Engineering
- Aftermarket Life Extension / Retrofits /
Modernization
- Turnkey Project / Project Management
Indonesia
EESS SEA
- Field Services
- Power Systems Engineering &
Automation
- Aftermarket Life Extension /
Retrofits / Modernization
- Turnkey Project / Project
Management
Australia
EESS ANZ
- Field Services
- Power Systems Engineering
- Automation & Access Control
- Aftermarket Life Extension
- Turnkey project / project
Management
New Zealand
IIEE of the Philippines
38th Annual Convention
© 2013 Eaton. All rights reserved.
November 2013
EESS China Organization
EESS
Field
Services
Application
Engineering
Project
Management
Power System
Engineering
Power System
Automation
PowerChain
Solution
Strategic
Marketing
Sales
PO
Coordination
Training
& Seminar
IIEE of the Philippines
38th Annual Convention
© 2013 Eaton. All rights reserved.
November 2013
EESS Scope and Value Offerings
Field
Services
• Start-up &
Commissioning
• Extended
Warranty
• Maintenance
Contracts (3-5
yrs)
• Testing &
General Field
Services
(planned
and ad-hoc)
• Renewal Parts
• 24/7 Response
• Power Quality
and System
Transient
Measuring
Power
System
Engineering
• Power System
Design, Audits,
Consulting
• Safety Studies
(Arc-Flash
Analysis,
Short Circuit &
Coordination)
• Power Quality &
Reliability
Studies
(Harmonics,
Transients,
Grounding)
• Power Flow
Study
PowerChain
Solutions
• Voltage Sag
Support
• Drive Voltage
Sag Ride
Through
Power
System
Automation
& Diagnosis
Systems
• Power
Monitoring,
Management and
Control Systems
• Electronic
Voltage
Regulation
• Partial Discharge
Predictive
Diagnostic
Systems
• Power Quality
Improvement
• Remote
Monitoring
• Harmonic
Mitigation
• Substation
Automation
• VFD
• SCADA Systems
• Soft Starter
• PLC Control
• Wireless
Communication
Turnkey
Projects
• Engineer,
Procure &
Construct (EPC)
• Conceptual
design
• Engineering
system studies
• Preparation of
equipment
specs
• Project
Management
• Construction /
Aftermarket
Life
Extension
• MV Breaker
Replacement
• LV Breaker
Replacement
• MCC motor
starter buckets
replacements
• Equipment
Rebuild and
Reconditioning
Alternative
Energy
Solar
• Feasibility
Audits
• Inverter with
Energy Storage
Capability
• Integration
• Engineering
• Commissioning
• Turnkey
• Retrofits,
Upgrades &
Modernization
installation of
the
equipment
• System start-up
(Load Flow, PF
• Performance
correction)
testing
• Dynamic Study
(Transient
Stability, Motor
Starting)
• Operators
Training
• Operation and
Maintenance
© 2013 Eaton. All rights reserved.
IIEE of the Philippines
38th Annual Convention
November 2013
EESS Value Prepositions
IIEE of the Philippines
38th Annual Convention
© 2013 Eaton. All rights reserved.
November 2013
VFD Principles and Selections
IIEE of the Philippines
38th Annual Convention
© 2013 Eaton. All rights reserved.
November 2013
How Does A VFD Vary the Frequency?
•
A VFD converts the AC supply to
DC using a rectifier (diode), then
converts it back to a variable
frequency by suing an inverter
bridge.
VFD Block Diagram
Motor
Main
Power
•
Six-diode rectifier converts
3-Ph utility power to DC.
•
Inverter section uses IGBTs
to convert DC power to a
simulated AC since wave.
•
Output voltage and frequency
can be controlled by inverter.
Capacitor
Rectifier
Switches
(IGBT’s)
Motor
IIEE of the Philippines
38th Annual Convention
© 2013 Eaton. All rights reserved.
November 2013
Volts per Hertz Regulation?
IIEE of the Philippines
38th Annual Convention
© 2013 Eaton. All rights reserved.
November 2013
Motor Speed/Torque Curve
•
Shows NEMA design B motor
torque vs. speed curve. Operating
point is pretty much fixed.
•
How to regulate motor torque at
different speed?
•
Changing the frequency of the
power applied to the motor
changes the speed/torque curve.
IIEE of the Philippines
38th Annual Convention
© 2013 Eaton. All rights reserved.
November 2013
Volts per Hertz Regulation
• A VFD can be used to control both the speed
and torque of a standard induction AC electric
motor.
• VFD can help to:
• Limit demand and electrical consumption of motors
by reducing the amount of energy they consume.
• Decrease mechanical stress due to pressure
spikes with direct on-line start & stop
• Reduce the starting current of the motor
IIEE of the Philippines
38th Annual Convention
© 2013 Eaton. All rights reserved.
November 2013
Principles of Selecting the VFD
•
Key points
•
Rated current:
•
Starting current, accelerating current, constant
speed current, decelerating current, .. The maximum
current that maybe appear will be the key basis
•
Capacity:
•
As the motor drive power supply, VFD needs to have a high capacity. In consideration
of economy, it’s not suitable to overestimate the rated capacity, but proper margin is
necessary, usually it’s greater than the motor rated capacity
•
Control strategy
•
•
SPWM, SVPWM, VC, DTC, etc.
Overload capacity
•
Overload capacity is the capacity that VFD can exceed the rated continuous output
current over a period of time
IIEE of the Philippines
38th Annual Convention
© 2013 Eaton. All rights reserved.
November 2013
VFD and Harmonic Issues
IIEE of the Philippines
38th Annual Convention
© 2013 Eaton. All rights reserved.
November 2013
What Are Harmonics
•
Take a perfect wave with a
fundamental frequency of 60Hz,
which is close to what is supplied
by power company.
•
Add a second wave that is five
times the fundamental frequency
– 300 Hz
•
Combine the two waves. The result
is a 60 Hz supply rich in fifth
harmonics.
IIEE of the Philippines
38th Annual Convention
© 2013 Eaton. All rights reserved.
November 2013
Harmonics Distortion from VFD
IIEE of the Philippines
38th Annual Convention
© 2013 Eaton. All rights reserved.
November 2013
Harmonic Contents from VFD and Other
Non-Linear Devices
IIEE of the Philippines
38th Annual Convention
© 2013 Eaton. All rights reserved.
November 2013
Examples of Harmonics
Frequency Conversion System in A Harbor
690V Bus A
690V Bus B
IIEE of the Philippines
38th Annual Convention
© 2013 Eaton. All rights reserved.
November 2013
Examples of Harmonics
•
IIEE of the Philippines
38th Annual Convention
© 2013 Eaton. All rights reserved.
November 2013
Examples of Harmonics
• Current THD > 50%, voltage THD > 7%
IIEE of the Philippines
38th Annual Convention
© 2013 Eaton. All rights reserved.
November 2013
Symmetrical Components and Harmonics
IIEE of the Philippines
38th Annual Convention
© 2013 Eaton. All rights reserved.
November 2013
Sequence Current and Sequence Torque
•
Motor damage, losses (heating) from “negative sequence
currents”.
•
High harmonics = low total power factor (utility penalties).
“Negative Sequence Current”
• Tries to Rotate Motor in
Opposite Direction
• Causes Motor Losses,
Heating and Vibrations
60 Hz Rotation
5th Harmonic
Rotation
IIEE of the Philippines
38th Annual Convention
© 2013 Eaton. All rights reserved.
November 2013
Examples of Power Reduction by Harmonics
• Flatted waveform and low power factor (87%)
IIEE of the Philippines
38th Annual Convention
© 2013 Eaton. All rights reserved.
November 2013
Harmonic Resonance
• Harmonic current magnifying problem.
•
Blown fuses
•
Failed capacitors
•
Damaged transformers
IIEE of the Philippines
38th Annual Convention
© 2013 Eaton. All rights reserved.
November 2013
Examples of Harmonic Resonance
Steel Mill - Pittsburgh, PA
• Harmonic Resonance - Capacitor Failure
IIEE of the Philippines
38th Annual Convention
© 2013 Eaton. All rights reserved.
November 2013
Examples of Harmonics
Automotive Assembly - Detroit, MI
• Large DC drives on stamping presses caused voltage notching
on 4 kV bus
IIEE of the Philippines
38th Annual Convention
© 2013 Eaton. All rights reserved.
November 2013
Harmonic Reduction Methods
IIEE of the Philippines
38th Annual Convention
© 2013 Eaton. All rights reserved.
November 2013
Harmonic Reduction Methods
•
•
•
•
•
•
•
•
•
•
•
Line reactor
Passive harmonic filters
Active harmonic filters
12-pulse converter
18-pulse converter (clean power drive)
Zero-sequence traps
Harmonic cancellation
Isolation transformers
Commutation reactors
200% neutral conductors
K-factor rated transformers
IIEE of the Philippines
38th Annual Convention
© 2013 Eaton. All rights reserved.
November 2013
Line Reactor
IIEE of the Philippines
38th Annual Convention
© 2013 Eaton. All rights reserved.
November 2013
Tuned Harmonic Filters
•
•
Application of passive filters
•
Parallel connection
•
Multiple filters
Commonly used passive filters
•
Single turnedd
•
Band pass
•
High pass
•
Damped
•
…
IIEE of the Philippines
38th Annual Convention
© 2013 Eaton. All rights reserved.
November 2013
12-Pulse Converter
IIEE of the Philippines
38th Annual Convention
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November 2013
18-Pulse Rectifier with Phase Shifting
Transformer
IIEE of the Philippines
38th Annual Convention
© 2013 Eaton. All rights reserved.
November 2013
Harmonic Reduction Methods
LEGEND
Incoming Utility Service
PFC
- Power Factor Correction
K
Active
HMT
MV
- K Factor Transformer
- Blocking Filter for Drives
- Harmonic Mitigating Transformer
MV Power Factor
PFC
Switchgear
- Tuned Filters
- Active Filters
- Blocking Filter for 3rd Harmonic
(optional harmonic filter)
LV Secondary
Unit Substation
- Multi-pulse Drives (12/18/24)
Active
Control/Sensing for
Active or Switched Filter
HMT
Transformer
K
w/Neutral Blocker
Feeding
Feeding
Computers
(3rd harmonics)
without Correction
Bus Voltage
with Correction
PFC
Active
PFC
MCC
Panelboard
Panelboard
Bus Voltage
120/208V
Harmonic Loads
Free Standing (AFD) Adjustable
PF Correction Frequency Drive
HMT
HMT
AF
D
AF
D
AF
D
M
M
M
Electronic
Ballasts
LV
Switchboard
With
Harmonic
Loads
© 2013 Eaton. All rights reserved.
and/or Harmonic (12/18/24 pulse)
Filter
IIEE of the Philippines
38th Annual Convention
November 2013
Eaton Product matrix of VFD
IIEE of the Philippines
38th Annual Convention
© 2013 Eaton. All rights reserved.
November 2013
Eaton VFD Segments Overview
• Machinery OEM Drives
0.25HP – 10HP
M-Max
• HVAC Drives
1HP – 250HP
HVX, H-Max
• General Purpose Industrial Drives
1.0HP – 250HP
SVX9000
• High Performance Drives
1.0HP – 2000HP
SPX9000, LCX, SPI
• Low Harmonic Drives
25HP – 800HP
CFX9000, CPX9000
• Medium Voltage Drives
SC9000
100HP – 5000HP
IIEE of the Philippines
38th Annual Convention
© 2013 Eaton. All rights reserved.
November 2013
Drive Low Voltage Ride Through
Support (DRT)
IIEE of the Philippines
38th Annual Convention
© 2013 Eaton. All rights reserved.
November 2013
Voltage Sag Problem
•
VFDs are susceptible to voltage sags and recloser operations
•
A short duration sag or interruption in voltage (1/10th of second) is
enough to cause an under
voltage trip on a VFD resulting in
minutes or hours of downtime and
production losses
•
Eaton’s DRT is an active voltage
conditioner that supplies regulated
voltage directly to de dc bus on a VFD
IIEE of the Philippines
38th Annual Convention
© 2013 Eaton. All rights reserved.
November 2013
DRT Solution
IIEE of the Philippines
38th Annual Convention
© 2013 Eaton. All rights reserved.
November 2013
Computer Modeling and Analysis to
Electrical Systems
IIEE of the Philippines
38th Annual Convention
© 2013 Eaton. All rights reserved.
November 2013
Computer Modeling and Analysis
• Build one-line diagram for harmonic analysis
IIEE of the Philippines
38th Annual Convention
© 2013 Eaton. All rights reserved.
November 2013
New Construction Considerations
• Before the system is built …
•
Build system model
•
Predict harmonics
•
Proposed solutions
•
Evaluate solutions
•
Size and place
•
Capacitors
•
Filters
•
…
IIEE of the Philippines
38th Annual Convention
© 2013 Eaton. All rights reserved.
November 2013
Existing System Considerations
• After the system is built …
•
Build system model
•
Take field measurements
•
Correlate to actual
conditions
•
Trouble-shoot system
problems
•
Size and place
•
Capacitors
•
Filters
•
…
IIEE of the Philippines
38th Annual Convention
© 2013 Eaton. All rights reserved.
November 2013
One-Line Diagram and Analysis Results
• Harmonic load flow study
• Display one-line results
• Analyze results
• Plots
• Harmonic indices
IIEE of the Philippines
38th Annual Convention
© 2013 Eaton. All rights reserved.
November 2013
IIEE of the Philippines
38th Annual Convention
© 2013 Eaton. All rights reserved.
November 2013