• Uninterruptable Power


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  • FileName: sept_22_10h.pdf [preview-online]
    • Abstract: unint***uptable powersupply (ups)introduction, batteriesand maintenance1 common terminologyac power : refers to voltage which cyclesfrom negative to positive levels withrespect to ground. this is what is typically

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unint***uptable power
supply (ups)
introduction, batteries
and maintenance
1
common terminology
ac power : refers to voltage which cycles
from negative to positive levels with
respect to ground. this is what is typically
supplied to most common types of loads.
dc power : refers to a steady state of
voltage. all batteries provide a dc output.
2
common terminology
ups : unint***uptable power supply
pdu : power distribution unit
battery bank : any number of batteries
connected in a series string.
rectifier : a device used for converting
ac power into dc power.
inverter : a device used for converting dc
power into ac power.
3
common terminology
ground : a reference point which
indicates a 0v level.
neutral : a conductor which provides a
return path for power.
single phase : 120, 240 vac power
supply.
three phase : 208, 480, 600 vac power
supply.
4
ups systems
the fundamental function of all ups
systems is to provide a source of power to
a critical load when the primary power has
been disrupted.
a secondary function of a ups system is
to provide power protection from voltage
fluctuations (i.e. brown outs, spikes…)
5
ups systems
static ups systems typically consist of the
following:
rectifier: converts ac to dc.
inverter: converts dc to ac
battery bank: provides a secondary source of
power.
static switch: a device which allows a power
bypass around the ups to occur.
6
ups systems
ups systems have three general modes
of operation:
normal operation
on battery
on bypass
7
technology features
igbt (insulated gate bipolar transistor)
enables high efficiency at full and partial load
conditions
pwm (pulse width modulation) enhanced with
space vector modulation
excellent output performance
digital control circuitry
16-bit microprocessor
computing resources for control of power module
regulation and ups event handling
dedicated ic model generator fully digital
stable output voltage wave form
less parts count
high output voltage quality even at highly non-linear
loads conditions
8
technology features
no potentiometers
easier parameters set-up through the monitoring system
more accurate and higher stability of installed values
digital phase locked loop (pll)
high output frequency accuracy and a more precise
synchronization between mains and inverter
high integration: single control board
improved serviceability
dsp (digital signal processing)
rapid response
digital rectifier regulation – controlled by microprocessor
hybrid digital & analog inverter regulation
9
what’s wrong with power
power experts, hydro utilities, ieee agree, that there are
9 common power problems that exist in our day to day
electrical systems
power failures high voltage spikes
power sags frequency variations
power surges switching transients
brownouts harmonic distortion
line noise
10
off-line ups
normal mode - utility present
utility
power
surge
suppression
emi/rfi
filters
load
battery
charger inverter
battery
• load is normally connected to utility
• load power does not flow through inverter
11
off-line ups
battery mode - utility outage, power problems
utility
power
surge
suppression
emi/rfi
filters
load
battery
charger inverter
battery
• 4 ms break in power to critical load
12
off-line ups features
• lowest initial cost
• basic power outage protection
• power failure
off-line • brownouts
• high voltage


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