Power supply

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UNINTERRUPTIBLE POWER SUPPLIES
JOHN LIGUORI CONSULTING ENGINEER MSEE, PE
PRESENTED TO THE IEEE LONG ISLAND CONSULTANTS
NETWORK 9/6/06
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UNINTERRUPTIBLE POWER SUPPLIES

• THIS PRESENTATION IS FOR INFORMATIONAL AND
  EDUCATIONAL PURPOSES ONLY. IT DOES NOT CONTAIN
  ALL INFORMATION REQUIRED, AND IS NOT INTENDED TO
  BE USED FOR THE SPECIFICATION OR DESIGN OF
  UNINTERRUPTIBLE POWER SUPPLIES (UPS) OR UPS
  SYSTEMS.

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UNINTERRUPTIBLE POWER SUPPLIESOUTLINE

• INTRODUCTION
• POWER DISTURBANCES
• UNINTERRUPTIBLE POWER SUPPLIES
• GENERAL DISCUSSION
• SUMMARY
• REFERENCES
• QUESTIONS

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INTRODUCTION

• PURPOSE
• WHAT IS AN UNINTERRUPTIBLE POWER SUPPLY?
• WHY USE A UPS?

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PURPOSE

• THE PURPOSE OF THIS PRESENTATION IS TO DISCUSS
  THE DIFFERENT TYPES OF UNINTERRUPTIBLE POWER
  SUPPLIES AVAILABLE, WHAT THE UPS PROTECTS
  AGAINST, THE COMPONENTS OF A UPS, AND ISSUES
  REGARDING SELECTION AND SIZING.
• THE DIFFERENT TYPES AND CAUSES OF POWER
  DISTURBANCES ARE DISCUSSED, AS WELL AS WHAT THE
  POWER UTILITY, THE ORIGINAL EQUIPMENT
  MANUFACTURER, AND YOU, CAN DO TO MINIMIZE THEIR
  EFFECT.

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WHAT IS AN UNINTERRUPTIBLE POWER SUPPLY?

• AN UNINTERRUPTIBLE POWER SUPPLY (UPS) IS A DEVICE
  THAT HAS AN ALTERNATE SOURCE OF ENERGY THAT CAN
  PROVIDE POWER WHEN THE PRIMARY POWER SOURCE IS
  TEMPORARILY DISABLED
• THE SWITCHOVER TIME MUST BE SMALL ENOUGH TO NOT
  CAUSE A DISRUPTION IN THE OPERATION OF THE LOADS

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WHY USE A UPS?

• PROTECTS AGAINST MULTIPLE TYPES OF POWER
  DISTURBANCES
• ONLY DEVICE THAT PROTECTS AGAINST AN OUTAGE
• OFFERS PROTECTION AGAINST
• EQUIPMENT NOT OPERATING PROPERLY
• COMPUTER AND EQUIPMENT DAMAGE
• DATA LOSS
• TIME AND EXPENSE TO RECOVER BACK TO WHERE YOU
  WERE, IF EVEN POSSIBLE

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POWER DISTURBANCES

• CAUSES
• TYPES
• DURATION
• RESULTING PROBLEMS
• COMMENTS
• WHAT THE POWER UTILITY CAN DO
• WHAT THE ORIGINAL EQUIPMENT MANUFACTURER (OEM)
  CAN DO
• WHAT YOU CAN DO
• PROTECTIVE DEVICES

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CAUSES OF POWER DISTURBANCES

• STORM ACTIVITY LIGHTNING, WIND, ICE
• OBJECTS COMING IN CONTACT WITH POWER LINE AND
  TRIPPING BREAKER TREE BRANCHES, ANIMALS, OTHER
• UTILITY FAULT CLEARING
• CONSTRUCTION ACTIVITY
• ACCIDENTS MOTOR VEHICLE, OTHER
• EQUIPMENT FAILURE
• OVERLOADING
• LOAD SWITCHING
• NON-LINEAR LOADS
• POOR GROUNDING
• ESD

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TYPES OF POWER DISTURBANCES

• INTERRUPTION
• SAG, UNDER VOLTAGE
• SURGE, OVER VOLTAGE
• VOLTAGE FLUCTUATION
• FREQUENCY VARIATION
• SPIKES / TRANSIENTS
• IMPULSIVE
• OSCILLATORY
• WAVEFORM DISTORTION
• DC OFFSET
• HARMONICS
• INTERHARMONICS
• NOTCHING
• NOISE
• VOLTAGE IMBALANCE

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DURATION OF POWER DISTURBANCES

• INSTANTANEOUS - ½ CYCLE (8 1/3 ms) OR LESS
• MOMENTARY - ½ CYCLE TO 3 SEC
• TEMPORARY - 3 SEC TO 1 MIN
• SUSTAINED - GREATER THAN 1 MINUTE

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CLASSIFICATION OF PROBLEMS RESULTING FROMPOWER
DISTURBANCES

• DISRUPTIVE
• EQUIPMENT DOES NOT OPERATE AS INTENDED
• DISSIPATIVE
• EQUIPMENT EXPERIENCES REPEATED STRESSES THAT LEAD
  TO FAILURE LATER FOR NO APPARENT REASON
• DESTRUCTIVE
• EQUIPMENT FAILS AT THE INSTANT THE DISTURBANCE
  OCCURS

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PROBLEMS RESULTING FROMPOWER DISTURBANCES

• DATA ERRORS
• DATA LOSS
• BLOWN FUSES
• TRIPPED BREAKERS
• INTERFERENCE WITH CONTROL OF LOADS
• OVERLOADED NEUTRAL CONDUCTORS
• MOTORS
• HEATING
• SPEED VARIATION
• STALLING
• AUDIBLE NOISE
• VIBRATION
• TRANSFORMERS
• HEATING
• AUDIBLE NOISE
• VIBRATION

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POWER DISTURBANCES - COMMENTS

• NOT ONLY IS MODERN EQUIPMENT MORE SUSCEPTIBLE TO
  POWER DISTURBANCES, BUT THE EQUIPMENT ITSELF
  GENERATES MORE DISTURBANCES
• ALL LOADS, FROM LARGE POWERFULL MOTORS AND
  INDUSTRIAL EQUIPMENT TO SMALL, SENSITIVE
  ELECTRONIC COMPONENTS, ARE CONNECTED TO THE SAME
  POWER GRID

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WHAT THE POWER UTILITY CAN DO TO MINIMIZE THE
EFFECT OF POWER DISTURBANCES

• INSTALL STORM RESISTANT WIRING
• USE INFRA RED SCANNING TO DETECT WEAK SPOTS IN
  POWER LINES
• INSTALL REMOTE CONTROLLED RADIO SWITCHES TO
  RESTORE POWER QUICKLY
• CLEAR TREE LIMBS AWAY FROM POWER LINES

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WHAT THE OEM CAN DO TO MINIMIZE THE EFFECT OF
POWER DISTURBANCES

• BUILD EQUIPMENT CONTAINING ONE OR MORE INTERNAL
  PROTECTIVE DEVICES
• SURGE PROTECTIVE DEVICES
• LINE FILTERS
• ISOLATION TRANSFORMER
• BATTERY OR CAPACITOR BACK UP TO INCREASE RIDE
  THROUGH TIME

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WHAT YOU CAN DO TO MINIMIZE THE EFFECT OF POWER
DISTURBANCES

• BUY EQUIPMENT THAT HAS INTERNAL PROTECTIVE
  DEVICES
• FOR EXAMPLE, BATTERY BACK UP FOR ANY APPLIANCE
  THAT CONTAINS A CLOCK
• USE ONE OR MORE EXTERNAL PROTECTIVE DEVICES
• SURGE PROTECTORS
• LINE FILTERS
• ISOLATION TRANSFORMER
• VOLTAGE REGULATING LINE CONDITIONER
• UPS

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PROTECTIVE DEVICES OTHER THAN UPS

• SURGE PROTECTIVE DEVICES SPDS
• PROTECTS AGAINST SPIKES OF LIMITED ENERGY
• METAL OXIDE VARISTORS MOV
• DIODES
• GAS TUBES
• LCR FILTERS
• HYBRIDS
• LINE FILTERS
• FILTERS OUT HARMONICS, TRANSIENTS AND NOISE
• ISOLATION TRANSFORMER
• ELIMINATES DC OFFSET AND NOISE
• VOLTAGE REGULATING LINE CONDITIONER
• AUTOMATICALLY ADJUSTS FOR UNDER AND OVER VOLTAGES
• CONSTANT VOLTAGE TRANSFORMER - CVT
• MOTORIZED VARIAC

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POWER DISTURBANCESANDPROTECTIVE DEVICES
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UPS

• ARCHITECTURES
• WAVEFORMS
• INVERTER TECHNOLOGY
• COMPONENTS
• SWITCHOVER TIME
• ADVANTAGES / DIS-ADVANTAGES
• SIZING
• BATTERY SAFETY

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UPS ARCHITECTURES

• LINE INTERACTIVE
• ON-LINE

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BLOCK DIAGRAMLINE INTERACTIVE UPS
CRITICAL LOAD (AC)
AUTOMATIC SWITCH
AC SUPPLY
BATTERY CHARGER
INVERTER DC TO AC
BATTERY
AC FAIL
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BLOCK DIAGRAMON-LINE UPS
CRITICAL LOAD (AC)
AUTOMATIC SWITCH
AC SUPPLY
CONVERTER AC TO DC
INVERTER DC TO AC
BATTERY
INVERTER FAIL
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BLOCK DIAGRAMLAPTOP COMPUTER POWER SUPPLY
CRITICAL LOAD (DC)
AC SUPPLY
CONVERTER AC TO DC
CONVERTER DC TO DC
BATTERY
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UPS WAVEFORMS

• TRUE SINEWAVE
• MODIFIED SINEWAVE
• SQUARE WAVE

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UPS WAVEFORMS
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INVERTER TECHNOLOGY FOR TRUE SINEWAVE

• PULSE WIDTH MODULATION - PWM
• LINEAR AMPLIFIER
• RESONANT INVERTER

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BLOCK DIAGRAMPWM INVERTER
DC POWER
CRITICAL LOAD (AC)
HIGH FREQUENCY GENERATOR
PULSE WIDTH MODULATOR
BASE / GATE DRIVE
TRANSISTOR BRIDGE
TRANSFORMER
FILTER
REFERENCE SINEWAVE GENERATOR
COMPARISON AMPLIFIER
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BLOCK DIAGRAMLINEAR AMPLIFER INVERTER
DC POWER
CRITICAL LOAD (AC)
SINEWAVE OSCILLATOR
TRANSFORMER
OSCILLATOR AMPLIFIER
COMPARISON AMPLIFIER
POWER AMPLIFIER
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BLOCK DIAGRAMRESONANT INVERTER
DC POWER
CRITICAL LOAD (AC)
SQUARE WAVE GENERATOR
SWITCH DRIVE
TRANSISTOR SWITCHES
TRANSFORMER
LC RESONANT TANK FILTER
(OR FERRORESONANT)
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UPS COMPONENTS

• CONVERTER - AC TO DC
• SPD - PROTECTS AGAINST SPIKES AND TRANSIENTS
• BATTERY
• STORED ENERGY DEVICE - PROTECTS AGAINST
  INTERRUPTIONS
• INVERTER DC TO AC
• WAVEFORM SYNTHESIS PROTECTS AGAINST DC OFFSET
  AND INTERHARMONICS
• FILTER PROTECTS AGAINST HARMONICS, NOTCHING AND
  NOISE
• VOLTAGE REGULATOR PROTECTS AGAINST SAGS, SURGES
  AND FLUCTUATIONS
• MONITOR AND CONTROL HARDWARE / SOFTWARE

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SWITCHOVER TIME

• A TYPICAL SWITCHOVER TIME 2 4 ms
• ONE QUARTER CYCLE OR LESS
• FOR SOME EQUIPMENT THIS IS NOT TOLERABLE

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ADVANTAGES / DIS-ADVANTAGES OF THE DIFFERENT UPS
ARCHITECTURES

• LINE INTERACTIVE ADVANTAGES
• AC TO DC CONVERTER / BATTERY CHARGER DOES NOT
  HAVE TO PROVIDE FULL LOAD POWER (POTENTIALLY
  CHEAPER)
• LESS STRESS ON DC TO AC INVERTER SINCE IT RUNS AT
  NO LOAD UNTIL UPS SWITCHES TO BATTERY POWER
  (POTENTIALLY CHEAPER)
• ON-LINE ADVANTAGES
• ZERO SWITCHOVER TIME FROM MAIN LINE TO BATTERY
  POWER
• ALWAYS ISOLATED FROM POWER DISTURBANCES ON THE
  MAIN LINE

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SIZING THE UPS

• EQUIPMENT RATINGS FOR LOADS
• OBTAIN RATINGS FROM NAMEPLATE OR SPEC SHEET
• ENERGY USAGE MAY BE SPECIFIED IN VOLT AMPS (VA)
  OR WATTS (W) AND IN VALUES THAT ARE EITHER
  MAXIMUM OR NOMINAL
• (VA) AND (W) ARE RELATED VIA THE POWER FACTOR
• TOTAL UPS LOAD MUST NOT EXCEED THE UPS VOLT AMP
  (VA) RATING
• TOTAL UPS LOAD MUST NOT EXCEED THE UPS WATT (W)
  RATING
• OVERSIZE / DERATE TO ADD LIFE
• RUNTIME CHARTS

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UPS SIZING EXAMPLE SPREADSHEET
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BATTERY SAFETY

• MAINTENANCE
• INSPECT PERIODICALLY
• REPLACE AS NEEDED
• RISKS
• ACID
• ELECTRIC SHOCK
• BURN
• FLYING, MOLTEN METAL (EYES)
• INJURIES RESULTING FROM CARRYING HEAVY BATTERY
  PACKS
• DISPOSAL
• DISPOSE OF PROPERLY
• RECYCLE WHENEVER POSSIBLE

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GENERAL DISCUSSION

• DOES A UPS OFFER COMPLETE PROTECTION?
• DO YOU THINK POWER DISTURBANCES WONT HAPPEN TO
  YOU ?
• MISCELLANEOUS

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DOES A UPS OFFER COMPLETE PROTECTION?

• SOME POWER DISTURBANCES MAY EXCEED THE HANDLING
  CAPABILITY OF THE UPS
• UPS FAILURE

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DO YOU THINK POWER DISTURBANCES WONT HAPPEN TO
YOU ?

• POWER DISTURBANCES OCCUR FREQUENTLY, THOUGH MANY
  ARE SMALL AND WITHOUT CONSEQUENCE
• AN ON-LINE UPS CAN PROTECT AGAINST MORE
  SIGNIFICANT POWER DISTURBANCES WHEN THEY DO OCCUR
• THE COST OF NOT HAVING A UPS CAN EASILY EXCEED
  THE COST OF A UPS

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MISCELLANEOUS

• MANY RETAIL UPS FOR COMPUTER APPLICATIONS ARE
  LINE INTERACTIVE
• MANUFACTURERS AND BUILDING CODES DO NOT ALLOW
  EXTENSION CORDS OR SURGE SUPPRESSORS TO BE USED
  WITH A UPS

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SUMMARYTHINGS TO CONSIDER WHEN SPECIFYING A UPS

• POWER QUALITY
• ARCHITECTURE - LINE INTERACTIVE OR ON-LINE
• WAVEFORM - SQUARE, MODIFIED SINE, TRUE SINE
• IMMUNITY TO DISTURBANCES OTHER THAN OUTAGE
• RUN TIME WITH AN OUTAGE
• RELIABILITY
• AUDIBLE NOISE
• MONITOR AND CONTROL HARDWARE / SOFTWARE
• LOCAL / REMOTE CONTROL
• INITIAL COST
• MAINTENANCE COST
• WARRANTY

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REFERENCES

• IEEE STANDARD 1100-2005
• RECOMMENDED PRACTICE FOR POWERING AND GROUNDING
  SENSITIVE ELECTRONIC EQUIPMENT
• IEEE STANDARD 1159-1995
• RECOMMENDED PRACTICE FOR MONITORING ELECTRICAL
  POWER QUALITY

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QUESTIONS