low voltage variable frequency drive (vfd) and related...

© 2013 Eaton. All rights reserved.

IIEE of the Philippines

38th Annual Convention

November 2013

Low Voltage Variable Frequency Drive (VFD) and Related Operation/Protection Issues

Eaton EESS APAC

JJ Dai, PhD, PE

November 2013




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




November 2013

EESS China Organization and

Businesses




November 2013

EESS APAC Footprint

Australia

New Zealand

Bangladesh

Bhutan

India

NepalPakistan

Sri Lanka Brunei

Indonesia

Japan

Laos

Malaysia

Myanmar

Philippines

Singapore

Taiwan

ThailandVietnam

China

Hong Kong

Korea Rep

Macau

Mongolia

EESS ANZ

- Field Services

- Power Systems Engineering

- Automation & Access Control

- Aftermarket Life Extension

- Turnkey project / project

Management

EESS India

- Field Services


- Aftermarket Life Extension /

Retrofits / Modernization

- Turnkey Project / Project

Management

EESS China

- Field Services


- Power System Automation

- PowerChain Solution

- Application Engineering

- Aftermarket Life Extension / Retrofits /

Modernization

- Turnkey Project / Project Management

EESS SEA

- Field Services

- Power Systems Engineering &

Automation

- Aftermarket Life Extension /

Retrofits / Modernization

- Turnkey Project / Project

Management




November 2013

EESS China Organization

EESS

Application

Engineering

Power System

Automation

Power System

Engineering

Project

Management

PowerChain

Solution

Strategic

MarketingSales

Training

& Seminar

PO

Coordination

Field

Services




November 2013

PowerChain

Solutions

EESS Scope and Value Offerings

• 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

Field

Services

• MV Breaker

Replacement

• LV Breaker

Replacement

• MCC motor

starter buckets

replacements

• Equipment

Rebuild and

Reconditioning

• Retrofits,

Upgrades &

Modernization

Aftermarket

Life

Extension

• Power System

Design, Audits,

Consulting

• Safety Studies

(Arc-Flash

Analysis,

Short Circuit &

Coordination)

• Power Quality &

Reliability

Studies

(Harmonics,

Transients,

Grounding)

• Power Flow

Study

(Load Flow, PF

correction)

• Dynamic Study

(Transient

Stability, Motor

Starting)

Power

System

Engineering

• Engineer,

Procure &

Construct (EPC)

• Conceptual

design

• Engineering

system studies

• Preparation of

equipment

specs

• Project

Management

• Construction /

installation of

the

equipment

• System start-up

• Performance

testing

• Operators

Training

• Operation and

Maintenance

Turnkey

Projects

• Power

Monitoring,

Management and

Control Systems

• Partial Discharge

Predictive

Diagnostic

Systems

• Remote

Monitoring

• Substation

Automation

• SCADA Systems

• PLC Control

• Wireless

Communication

Power

System

Automation

& Diagnosis

Systems

Solar

• Feasibility

Audits

• Inverter with

Energy Storage

Capability

• Integration

• Engineering

• Commissioning

• Turnkey

Alternative

Energy

• Voltage Sag

Support

• Drive Voltage

Sag Ride

Through

• Electronic

Voltage

Regulation

• Power Quality

Improvement

• Harmonic

Mitigation

• VFD

• Soft Starter




November 2013

EESS Value Prepositions




November 2013

VFD Principles and Selections




November 2013

How Does A VFD Vary the Frequency?

Switches

(IGBT’s)

VFD Block Diagram

Motor

Main

Power Rectifier

Capacitor Motor

• 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.

• 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.




November 2013

Volts per Hertz Regulation?




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.




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




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




November 2013

VFD and Harmonic Issues




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.




November 2013

Harmonics Distortion from VFD




November 2013

Harmonic Contents from VFD and Other Non-Linear Devices




November 2013

Examples of Harmonics

690V Bus A 690V Bus B

Frequency Conversion System in A Harbor




November 2013


•




November 2013


• Current THD > 50%, voltage THD > 7%




November 2013

Symmetrical Components and Harmonics




November 2013

Sequence Current and Sequence Torque

• Motor damage, losses (heating) from “negative sequence

currents”.

• High harmonics = low total power factor (utility penalties).

60 Hz Rotation

5th Harmonic

Rotation

“Negative Sequence Current”

• Tries to Rotate Motor in

Opposite Direction

• Causes Motor Losses,

Heating and Vibrations




November 2013

• Flatted waveform and low power factor (87%)

Examples of Power Reduction by Harmonics




November 2013

Harmonic Resonance

• Harmonic current magnifying problem.

• Blown fuses

• Failed capacitors

• Damaged transformers




November 2013

Examples of Harmonic Resonance

Steel Mill - Pittsburgh, PA

• Harmonic Resonance - Capacitor Failure




November 2013


Automotive Assembly - Detroit, MI

• Large DC drives on stamping presses caused voltage notching

on 4 kV bus




November 2013

Harmonic Reduction Methods




November 2013


• 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




November 2013

Line Reactor




November 2013

Tuned Harmonic Filters

• Application of passive filters

• Parallel connection

• Multiple filters

• Commonly used passive filters

• Single turnedd

• Band pass

• High pass

• Damped

• …




November 2013

12-Pulse Converter




November 2013

18-Pulse Rectifier with Phase Shifting Transformer




November 2013

MV Power Factor

(optional harmonic filter)

MV

Switchgear

Incoming Utility Service

LV Secondary

Unit Substation

Transformer

w/Neutral Blocker

LV

Switchboard

With

Harmonic

Loads

MCC

(AFD) Adjustable

Frequency Drive

(12/18/24 pulse)

Panelboard

Feeding

Computers

(3rd harmonics)

PFC

PFC

Active

HMT HMT

AF

D

M M M

PFC

Free Standing

PF Correction

and/or Harmonic

Filter

K

AF

D

AF

D

HMT

Panelboard

Feeding

120/208V

Harmonic Loads

- Power Factor Correction

- Tuned Filters

PFC

- Active Filters

- Harmonic Mitigating Transformer

- Blocking Filter for 3rd Harmonic

- Multi-pulse Drives (12/18/24)

Active

HMT

- Blocking Filter for Drives

- K Factor TransformerK

LEGEND

Electronic

Ballasts

Active

Control/Sensing for

Active or Switched Filter

Bus Voltage

without Correction

Bus Voltage

with Correction





November 2013

Eaton Product matrix of VFD




November 2013

Eaton VFD Segments Overview

• Machinery OEM DrivesM-Max 0.25HP – 10HP

• HVAC DrivesHVX, H-Max 1HP – 250HP

• General Purpose Industrial DrivesSVX9000 1.0HP – 250HP

• High Performance DrivesSPX9000, LCX, SPI 1.0HP – 2000HP

• Low Harmonic DrivesCFX9000, CPX9000 25HP – 800HP

• Medium Voltage DrivesSC9000 100HP – 5000HP




November 2013

Drive Low Voltage Ride Through

Support (DRT)




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




November 2013

DRT Solution




November 2013

Computer Modeling and Analysis to

Electrical Systems




November 2013

Computer Modeling and Analysis

• Build one-line diagram for harmonic analysis




November 2013

New Construction Considerations

• Before the system is built …

• Build system model

• Predict harmonics

• Proposed solutions

• Evaluate solutions

• Size and place

• Capacitors

• Filters

• …




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

• …




November 2013

One-Line Diagram and Analysis Results

• Harmonic load flow study

• Display one-line results

• Analyze results

• Plots

• Harmonic indices




November 2013

low voltage variable frequency drive (vfd) and related...

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