Ups Presentation30

7/28/2019 Ups Presentation30

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UPS PRESENTATION

BMARC2-7-2010

Chuck VK2SS


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What does UPS stand for ?

1 . Useless pile of shite ?

2. United parcel service ?

3. Uninterruptible power supply ?

Yes its Uninterruptible power supply .


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Why do we need a UPS ?

1. To keep critical systems running during mainsdisturbances .

What are some examples of a critical system ?

1. Security companies .

2. Financial institutions .

3. Military installations .

4. Hospital operating theatres .

5. Government .

6. Telcos


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Mains Disturbances

1. Sags and surges .

When the mains voltage goes outside of the normal tolerance of + -10 % for more than a few seconds .

2. BrownoutsWhen the mains voltage dips below 10 % of the nominal for

a few seconds .

3. Impulses .

A short duration pulse which can be of a very high amplitude .

4. Outage .When the mains voltage drops to a very low level or to zero .


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How do we protect against thesedisturbances ?

1. Older systems used power conditioners whichwere basically A/C voltage regulators with spike andnoise suppression . There were two basic types,

Tap changers and ferro resonant .The tap changer switched taps using triacs on atransformer. Ferro used a capacitor in conjunction

with a transformer winding to create a resonant circuit. Regulation and noise rejection was excellent butthey were inefficient .


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Static UPS

Rated up to about 800kVA per unit .

Can be setup as a single or stand aloneUPS .

Or parallel redundant N+1

Or parallel for capacity N+N .


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Protection by UPS

Nearly all modern power protection is done byUPS .

There are basically two types of static UPS :

On line or double conversion .Standby or NBPS or single conversion .


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30kVA IndustrialUPS


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200kVA with 3 X40 batteries .


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6 Kvasinglephase


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Rotary UPS

Rated to 1.5 Mva per unit .

Is basically a motor with a 4 tonne flywheelwhich stores mechanical energy that powers agenerator . During a power outage the rotatingflywheel starts a diesel engine to power thesystem .

Sony in Japan has a site using 40 x 1.5mVAunits .


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Standby or single conversion.

If mains is within tolerance the critical load issupplied via the mains with some power conditioning .

If mains is out of tolerance the inverter isswitched on and takes the load after a smallbreak . Another version is called line

interactive which can boost or buck themains voltage with say a 5% variation .Outside this the inverter will run .


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Standby UPS


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Line interactive UPS


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On Line UPS

The inverter is on line all the time .

Being double conversion AC/DC then DC/ACit gives very good immunity to mainsdisturbances .

When mains goes outside of tolerance theinverter runs on battery power .


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UPS Modules

Rectifier

Uncontrolled bridge .

SCR phase controlled bridge .

Active rectifier which is basically an inverter in reverse .


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Rectifier Types

A single phase half wave rectifier is a 1 pulsecircuit .

A single phase full wave rectifier is a 2 pulsecircuit .

A three phase full wave rectifier is a 6 pulse .

A 3 phase full wave with a 30 deg tx is a 12pulse circuit .


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Full Wave Rectifier

Click to edit Master text stylesSecond level Third level

Fourth level Fifth level


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Rectifier


Fourth level Fifth level Draws current from

the mains in narrow

pulses to charge thecapacitor .

This creates reflected

harmonics back intothe mains .


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3 Phase 12 Pulse Rectifier

Click to edit Master text stylesSecond level

Third level Fourth level

Fifth level

Has much lower reflectedTHDi asthe 2 rectifiers combine toproduces 12 pulse operation. This rect. is shifted 30

deg due to the star

delta transformer .


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Power Device Symbols



Fifth level


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Active Rectifier

Uses IGBTs and looks like an inverter inreverse .

Can work at power factor of unity andgenerates very low THD figures .

More acoustic noise than a conventionalrectifier .


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Active Rectifier



Fifth level


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Inverter

Square and quasi square . Has poor THD asa square wave contains all frequencies.

Not compatible with all loads and willproduce a buzz in speakers .

Sine wave is much more compatible with allloads . Normally generated by PWM .


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Square Wave Inverter


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Inverter

Older types operated into an outputtransformer ,which offers some isolation fromthe load but theres a weight penalty.

Newer types are transformer less so are moreprone to load related issues such as DCfeedback . They also require a boost circuitafter the rectifier as the rectified mainsvoltage is not quite high enough to give 240Vout .Smaller footprint and lighter


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H Bridge Inverter



Fifth level


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Inverter PWM



Fifth level


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PWM Generation

Older versions used analogue methods.Basically a triangular waveform called thecarrier , typically 6kHZ is compared in acomparator with a 50hZ sine wave .

Newer versions use DSP with jee wizalgorithms and give excellent sine wave A/Coutput .


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Inverter Power Devices .

SCRs were used in the older inverters but werenoisy and inefficient .

BJTs are a current fed device so the base driverequirements are difficult . Parallel transistors hadto be matched so they would load share .Switching frequency was limited.

Mosfets are still used in small UPS .

IGBTs are a voltage fed device so much easier to drive and do not need to be matched for parallel operation .


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500A IGBT


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300A BJT


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70uF 3PhaseFilter

Capacitor


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315ASemiconductor fuse .


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500ABlade

fuse


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Static Switch

Is a solid state A/C switch using back toback SCRs . One SCR conducts on the Poshalf cycle and the other on the neg half cycle .

Its used to switch the reserve supply or theinverter supply to the load without a break .


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IN/OUT

IN/OUT

STATIC SWITCH


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Bottom trace indicates transfer point .


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130A Double

SCR


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Batteries

Supply the power to the A/C load during amains outage .

UPS mostly use VRLA batteries . There asome wet cell sites .

Wet cells are rarely used as they requirespecial site conditions such as vent fans andemergency showers .


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A voltage is produced due to the reaction of the sulphuric acid , which forms theelectrolyte , and the spongy lead plates .

During charge the acid is driven from theplates into the electrolyte and the s.g. of theelectrolyte rises to around 1280 .

During discharge the acid is driven from theelectrolyte into the plates reducing the s.g .down to 1100 or so .

Batteries


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Battery Capacity

CCA

Is the current that the battery can deliver for 15seconds while maintaining at least 9 terminalvolts . Its for starter applications .

Amp hrs .Is the amps that a batt can give at either the10hr or 20hr rate . 10A for 10hrs = 100Ah


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Battery Capacity

Watts/cell

This is more related to UPS applications asthe load has a constant power characteristic .

Manufacturers produce charts of dischargecharacteristics , which are for constantpower , or current , versus time .


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Sizing Batteries

In UPS applications battery loading is calculated onthe Kw not the Kva load .

From the A/C Kw load add the UPS efficiency figure. Eg :1000W+ 8%=1080W

Calculate the W/cell eg: 1080/(6cells per batt X 8batts) 1080/48= 23 w/cell .


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Sizing Batteries

From the eg:

GP12-72 disch chart lookup the autonomyrequired time .

This gives 20 mins discharging to 1.65 v/cell .

If 60 mins was required we find that a GP12-340disch to 1.65v/cell is suitable .

If 180 mins was required we find that a GP12-650 disch to 1.7v/cell is suitable .


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Sizing Batteries

Wet cell car batteries are mainly designedfor starter application as once the motor isstarted the alternator takes the load .

Theyre not designed to be discharged toless than 50% capacity and rarely get to90% capacity .

This only leaves 40% available capacity soa 100aH batt becomes a 40aH batt .


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Sizing Batteries

Deep cycle and VRLA batteries are designed to bedischarged to a lower level.

Repeated deep discharges will still reduce thebatterys life .

VRLA batteries are rated under normal use and

normal temperatures to have an end of life capacityof 80 % of sol capacity.


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Average Disch Cycles



Fifth level


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Positive Power

Positive and NegativePower


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Power Factor


Fourth level Fifth level


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P F


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Power Factor

To keep within the output limitations mostUPS and other power generating equipmentfactor in a de rating figure depending on the

pf of the load .

Eg: A 20kVA UPS will produce 16kW at unitypf . It will produce 20kVA at 0.8 lag but only18kVA at 0.8 lead .

Si i UPS


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Sizing a UPS

What power is required kVA and kW?

Is the load of a linear nature or likely to havea high peak factor ?

Will the load have a high inrush current

Eg : motor starting ?

What battery autonomy is required with thisconnected load ?

Si i UPS


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Sizing a UPS

Small UPS do not like laser printers due tothe heating elements .

Loads that produce a DC component eg :Electric drills will upset small UPS due to theDC getting back to the load sensing circuitsas theres no output TX .

Running an online UPS from a generator islikely to cause a synch. alarm due to thefrequency variations of the generator .


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Phaserotationmeter


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Wrap aroundtong

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