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Safeguards that Improve Your Bottom Line
The year 2001 will surely be remembered,
as is 1941 when the US finally emerged out of the throws of
one crisis with the Great Depression and into another with
our entry into a devastating Global War. During 2001, we have
gone from a spring/summer power crisis in our most populated
state, California, to our national late summer/fall disaster
of 9-11. Now we engage in another war, but unlike others during
the last century, this crisis has affected our homeland with
a direct assault and war front. Our emergency preparedness
plans are being re-evaluated, especially preparedness for
bioterrorism. However, we also have to assure that our laboratories
will be able to function at all times. This means that electrical
power preparedness is fundamental and becomes an even greater
part of the lab’s foundation for contingency planning.
It is quite likely, if the laboratory has
not already done so, that the Laboratory Manager (LM) or Principal
Investigator (PI) will update a number of critical operating
procedures and install safeguards to assure the lab’s:
availability, reliability and survivability. This includes
installing or upgrading supplemental electrical power devices,
which is a wise choice to guarantee that the lab will not
default on its contractual obligations to produce timely quality
analyses and reports. While nearly all mission critical labs
have emergency backup generators, these supplemental power
systems are not really helpful if the analytical processing
of samples, or the analyzers themselves, go offline due to
a very limited time power interrupt (glitch) or total short
term power loss, while transitioning to other backup sources.
Improving the overall utilization and efficiency of the lab’s
electrical power is a bonus during preparedness upgrades.
These investments will pay off by reducing down time and services
costs associated with poor power quality that is being utilized
by the lab’s instrumentation systems.
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Assuring the availability,
reliability of results and survivability of the laboratory
is the primary emergency preparedness goal
Electrical power preparedness
becomes an even greater part of the laboratory’s
contingency planning
Gaining increases in
availability and ROI are the benefits
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The impact to the
lab’s operating bottom line for poor power quality or
power interrupts is lost profit margins, increased operating
costs, lost reporting time and possible damage to the instrumentation.
But here’s the rub, very few labs and instrumentation
manufacturers are in a position to determine and/or advise
which is the best solution for improving power quality and
integrity. Installing online uninterruptible power devices,
that condition the lab’s power, while providing supplemental
(backup) power reserves is not as easy as adding a surge protector
to a computer. The reason is simple; the instrumentation manufacturers
like the laboratory are power users and not power consultants,
so the lab is usually on its own to resolve its contingency
planning and lab power management. As the old adage indicates,
every “dark cloud” does have “a silver lining”
and that is the good news. The bright side of this contingency
planning dilemma is that installing a quality Laboratory Protection
System (LPS)
that is truly online (100% online – without a switch
over lag to reserve power), with sufficient supplemental battery
power reserves, will actually save the laboratory money. The
LPS
will improve power within the lab and aid in boosting its
operating margin. Case studies indicate that the lab can expect
an attractive ROI and Cost/Benefit ratios between 5 and 15:1.
What this means is that the
investment in LPS units provides a positive bottom line return
you can realize right away!1,2
This article's purpose is to assist the
LM and/or PI in understanding laboratory power terminology
and the differences between Watts, VA, VARs and TPF when evaluating
their contingency plans for electrical power products and
solutions. An additional goal is to guide the LM or PI in
understanding how the terms are correctly and incorrectly
used when specifying AC power protection interface and improvement
devices. Nearly all of us are confused about the distinction
between the Watt and Volt-Amp (VA) measures for external and
interface Laboratory Protection System (LPS/UPS)
load sizing, when the system manufacturer has not directly
recommended or specified a “certified”
instrumentation-grade LPS. This is an important issue,
since the terminology in the literature is confusing and misapplied.
The issue with power and power protection is that to truly
understand AC power you do need a technical background in
power/energy engineering. The problem is that you do not have
the time for an extensive study and you need to put a contingency
plan in place NOW!
Now that the LM and/or PI have decided
to take positive action in reviewing their contingency plans,
a new set of power terminology, associated with purchasing
electrical power products, must be understood. The explanations
and definitions within this article provide a basic understanding
of how AC power is defined, for laboratory applications. The
goal is to discuss the power environment, without becoming
complex. Key technical terms have been highlighted. The reviewer
will derive sufficient information from this article to better
understand the engineering implications of inappropriately
sizing and applying AC power interface protection to instrumentation.
Supplemental electrical energy/power source (backup) systems
and LPS units are a necessity in any commercial, R&D and
production lab. Truly, 100% online uninterruptible power protection
is specifically required for key mission critical communications
and instrumentation defined under Category II
or III applications.
Power Definition Background for all Alternating
Current Applications3
While understanding “power”
in DC applications is straight forward as: (DC Volts) x (Amps)
= Watts, “AC power”
is and entirely different matter. AC power drawn by analytical
laboratory instrumentation, computers, telecommunications,
digital controllers, and/or other general-purpose lab equipment
is expressed in a number of unique terms identified in the
table below:
| Term |
Abbreviation
/ Usage |
| Active Power |
Watts, W,
KW |
| Apparent
Power |
Volt-Amps,
VA, KVA |
| Apparent
Power Factor (without reactance) |
APF or Cos
(phi) or PF |
| Demand Power |
VA |
| Displacement
Power Factor (without harmonics) |
DPF, Cos
(theta) or PF |
| Harmonics
(linear) |
THD, Total
Harmonic Distortion |
| Linear |
Aligned Frequency
of Volts and Amps (within phase) |
| Measured
Power Factor |
Ratio of
measured Apparent Power Factor to the W for linear application
(without reactance) |
| Non linear |
Volts and
Amps are out of phase |
| Power (general) |
Work (Energy)
per unit time |
| Power Factor
(general) |
PF, Cos (theta),
DPF, Cos (phi), APF |
| Reactive
Power |
VAR (Inductive
or Capacitive) |
| Real / True
Power |
W |
| Total Power
Factor |
Sum of DPF
+ APF, total measure of the efficiency of power utilization |
| Volt-Amps |
VA |
| Volt-Amps
Reactive |
VAR, KVAR
(Inductive or Capacitive) |
| Watts |
W, Power
to do useful work / t |
Watts (W), Volt-Amps
(VA), (VARs), Power Factor (PF, DPF, Cos (theta) and APF)
and Harmonics are the
principal AC power terms. The power in Watts
is the “real/true power”,
also known as “active power”
drawn by the instrumentation, laboratory device and/or other
equipment (load device) of interest. This is the power that
produces useful work (energy), during a time period. By definition
Power = Energy / t, but to truly
understand electrical power in AC applications, you have to
look at both Power Factor and
Harmonics together, especially
if the discussion involves instrumentation and its associated
systems.
Volt-Amps (VA)
is called the "apparent power"
and is the product of the AC voltage applied to the load times
the current drawn by the load. Additionally, magnetic and
electrical energy (per unit time) is stored within the load
device along with the “active power (which includes heat
losses)” to form the total demand on the utility. “Apparent
power” is also known as “demand
power”, since this is the power the utility must
supply to its customer. Demand (apparent) power will always
be greater than the active (real/true) power required to do
real work, within a given time period.
The only exception to this is where the
load is purely resistive, without additional energy storage
in the form of “reactive power”
(magnetic fields induced by inductors and electrical fields
generated by capacitance); and without
“harmonic distortion”. In laboratory and
instrumentation device applications, the load is never truly
resistive or “linear”
(where voltage and current frequency rise and fall together,
i.e. within phase and without distortion) Therefore, there
will always be some value of “apparent/demand power”
and this value will be greater than the “active/real
power”. Refer to Figure 1 for the Power Relationship
triangle.4
Figure 1: Power Relationships (W, VA, VARs
& PF)
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Apparent Power (VA) is
the vector product addition of Real Power (W) and Reactive
Power (VAR)
Apparent power is what
you pay for and real power is what is used to do something
useful. The energy/power that you cannot use because
of low Power Factor is converted into heat losses in
the wiring and circuitry
PF = 1. 0 is an ideal
situation, where: Apparent Power = Real Power
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Both Watt and VA (VARs) ratings have an
important use and purpose in electrical and energy engineering
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The W and VA relationship
forms the key for appropriately specifying and sizing
True Online Power interface protection devices for any
lab application
The VA (KVA) rating is
generally specified for the instrumentation system.
What is equally important to know is the active power
in Watts; and this information is not readily available
within the laboratory
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The relationship between the apparent and
real (active) power is also known as the Power
Factor (PF), which is also alternatively described
as Cos (theta). Displacement
Power Factor (DPF)5
is the term used to describe and measure the effects of inductance
(motors, ballast, coils and transformers) and capacitance
on the efficiency of the AC distribution system, without
harmonic distortion. Total Power
Factor (TPF) is used to describe the total inefficiency
of the load or distribution network, when linear harmonic
distortion is introduced into the application. PF
as a general term is now used incorrectly, or more so incompletely,
in describing combined complex “analog” and “digital”
systems, as a measure of efficiency and effectiveness of the
load device. TPF is better term
to use regarding the measure of the DPF
of the classical analog non-linear
loads (sinusoidal with a phase shift, due to inductance and
capacitance) and the linear
harmonic distortion of high speed switching equipment (controllers,
processors and computers).
The Power Factor (DPF) relationship from
Figure 1 can be expressed as:
VA = Watts / Power Factor
Power Factor = Real
Power / Apparent Power
Power Factor (PF,
Cos (theta) or more specifically DPF)
by electrical definition (IEEE)6
is actually determined as the cosine of the leading or lagging
phase angle (theta) of the fundamental of the current to the
voltage. Equipment that stores energy, or requires a large
ramp up to develop a square wave digital signal (infinite
harmonics), such as a switched mode power supply (SMPS),
in a computer or digital system, provides no real or useful
work, but it does require appropriate sizing of the circuitry
to handle the large current loads. ”Apparent
Power Factor”7,
by definition, is the cosine of the phase angle (phi) of the
measured line KVA, due to harmonics.
Harmonic distortion and reactive current loads generate heat
within the conductor and affect wiring insulation temperatures.
High insulation and wiring temperatures can cause a safety
hazard and must be limited.
Figure 2: Active
Power (Delivered Power) Resulting from Non Linear (Out of
Phase) Loading
Figure 2 illustrates an example of a non-linear
load with reduced real (active) power delivery. This type
of device is storing a combination of principally magnetic
and electrical energy (reactance)
internally with no useful work being produced. The reactance
energy/power is being converted into heat. Reactance is due
to the phase shift of the true sine wave (undistorted) current
to the voltage. Analytical instrumentation with large inductive
loads such as, centrifuges, motors, coils, solenoids, lasers,
fluorescence/UV flash lamps, etc. will exhibit reactive power
delivery requirements similar to the area under voltage and
current curves (yellow highlighting), shown in Figure 2. In
the traditional or classical sense, with truly reactive power
(VARs) and no harmonic distortion, power factor is simply
the cosine of the phase angle (theta) between the voltage
and current waveforms. This phase angle is correctable, as
we will see shortly.
However, this is only part of the story
affecting analytical instrumentation. The second phenomenon
in bringing digital control, automation and robotics into
the laboratory is the addition of the other form of power
factor (apparent power factor) induced by digitally switched
equipment. As we all seek higher speed in our computers, laboratory
automation and other digital processors, we are also making
our business applications vulnerable to the nemesis of induced
harmonic distortion. Harmonic distortion is fed back
into the laboratory’s or business application’s
power distribution network as reflected return on the electrical
distribution system’s neutral wiring. This reflection
back into the laboratory’s distribution system means
that all instrumentation and systems now have the opportunity
to share distorted voltage and current waveforms.
Engineered/Certified
LPS systems correct for harmonics.
Figure 3: Harmonically
distorted current wave form
While the SMPS
is a linear device in the sense that current and voltage are
in phase, the resulting power factor (.6PF
typically) for such a digital device is very low. This inefficiency
is primarily due to the SMPS'
high frequency switching which results in harmonic distortion
of the current waveform.
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Figure 3 illustrates
a linear load (in phase with voltage), but a harmonically
distorted current waveform with just the application
of the fundamental (60 Hz), 3rd
(180 Hz) and 5th (300
Hz) harmonics. All of these waves are superimposed to
produce the resulting current harmonic waveform
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In today's contemporary digital load environment,
power factor is also a measure of the Total
Harmonic Distortion (THD) in the current waveform.
Refer to Figure 3 for an example
of a simple harmonically distorted current waveform with only
the superposition addition of the fundamental, 3rd
and 5th harmonic. Switching
at the high frequency levels (1 GHz) of today’s digital
processors requires very high current draws and results in
high switching transients.
How Do You Correct the Lab’s Power
Problem ?
The laboratory’s power problem can
be corrected in a number of relatively simple ways. To do
it effectively, however, the LM or PI must be aware of what
his/her “power consultants” are advising to assure
a fix. Otherwise, the resulting power “solution”
can have a seriously aggravating effect, resulting in damage
to the interface devices, instrumentation systems, as well
providing a safety hazard to the laboratory and its staff.
Correcting power delivery to an instrument and the laboratory
is an “engineered application”. This is one of those
probable situations where a little bit of “education”,
or lack of it, on the part of the specifier can provide a
serious economic set back to the laboratory; and may even
more so leave the lab without the power protection and correction
that was originally desired/required. An engineered (laboratory)
application requires an engineered solution. The LM and/or
PI are recommended to seek the assistance of the system manufacturer
and/or a known LPS manufacturer and power consultant, to provide
an engineered and certified instrumentation grade solution.
The ubiquitous centrifuge that is required
in all human and animal health, clinical and drug discovery
labs is one of the largest generators of high reactance power
(VAR) from its motors. In addition, the inrush current to
bring the centrifuge up to speed is up to nine times the normal
running current required for this non-linear load. The main
drive for the centrifuge rotor is an induction motor. Coupled
with vacuum pumps and refrigeration for the ultra high “G”
loading systems operating at over 90,000 RPM and you have
a classic case of low Power Factor due to high reactance power
draws. Left unchecked, the out of phase current to voltage
is reflected back into the lab disturbing the power to the
rest of the lab’s instrumentation. This problem can be
corrected in a number of ways:
- Check with equipment manufacturer to
assure that the power factor for motor applications (refrigeration,
centrifuges, vacuum pumps, etc.) are specified with greater
than .90 PF, to eliminate
the need for these types of capacitor applications.
- Apply a LPS system to correct all of
the reflected harmonics and non-linearity between voltage
and current, that is affecting the lab’s power distribution
system.
- If necessary, Power Factor (DPF)
correction capacitors, for this type of inductance load,
are usually applied close to the source to bring the voltage
and current phase angle back into phase synchronization.
Adding boosting capacitors to an inductance
application is acceptable as long as harmonic distortion is
not present (microprocessor controlled centrifuges, instrumentation,
et al), otherwise serious capacitor damage will result due
to internal resonance.
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Beware of applications
where there are significant harmonics (variable frequency
devices and other non-linear loads). The harmonics can
cause resonances with the capacitors and damage them.
If harmonics exist, consider harmonic filters, which
also typically improve the load8.
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While this solution has solved one problem,
it has not really addressed the real TPF
issue, which includes harmonics. All labs and their key respective
instrumentation systems are filled with various power inefficient
devices. These devices are “harmonically polluting”
by reflecting waves back into the laboratory’s AC power
distribution system. Additionally the EPRI
(Electric Power Research Institute) recommended in its recent
address to the US Congress, that power interface devices (LPS)
be installed in critical applications to bring the power quality
to the necessary minimum levels specified by the instrumentation
and equipment manufacturers9.
Since laboratories also need to update their contingency management
plans, particularly now with the bioterrorism initiatives
being supported by the US Government, an uninterruptible and
supplemental power solution, that also address power factor
inefficiency and harmonics (TPF)
is highly recommended. In particular, a Laboratory
Protection System (LPS) specifically designed to correct
reactive power and harmonics, with high TPF
(>.9TPF); including VHF/UHF harmonic filtering for
instrumentation, is the most preferable. Additionally, these
interface devices operate with true
zero switch over time (true 100% online) to provide
required supplemental energy/power reserves and protection.
Not All Uninterruptible and Supplemental
Power Solutions are Suited for Instrumentation
Because of the unique loads required by
instrumentation applications, not all
UPS devices, especially those designed for the consumer
PC computer market or marketed as lower cost “hybrid
on-line”, are suitable to protect
key Category III systems. Certified
LPS products, however, are purpose built engineered
power systems, configured and qualified/tested to assure 100%
performance in the laboratory’s instrumentation environment.
The IEEE and IEC have categorized LPS/UPS units according
to their design functions and IEEE UPS Category 3 “Regenerative
(True) Online, Sine wave – with precision line &
load regulation”10 designs
are recommended for mission critical instrumentation applications.
These LPS instrumentation grade
systems are identified as Category
III –311.
Selecting a suitable Category
III–3 LPS for the laboratory’s particular
instrumentation make & model, where continuity of load
power - while providing output voltage and frequency independent
of input voltage and frequency, is an economically wise step
managing the lab’s bioterrorism contingencies. The additional
benefit of specifying a LPS
with Power Factor corrected to .95
TPF assists in maximizing the performance of the protected
instrumentation system, availability and reliability of test
results, while reducing the laboratory’s total cost of
operation. The true benefit to the lab is that the investment
in this type of power protection equipment is an economically
smart decision. LPS systems
protect the lab’s key investment in instrumentation and
staff, correct power inefficiencies and effectively eliminate
harmonic distortion (< 2% THD). Instrumentation availability
and reliability substantially improves by providing very clean
and highly regulated power to the equipment. Realizing a ROI
in less than two or three months, by adding a safeguard, like
a LPS that drops savings right
to the lab’s bottom line, is truly the added bonus of
smart lab management.
About the Author
Raymond L. Hecker, MBA, BS Engineering is Vice President,
Franek Technologies, Inc. (FTI), the leading specialty LPS
manufacturer for scientific and healthcare instrumentation
systems. Mr. Hecker has worked for Fortune 100 Organizations
including Roche/Boehringer Mannheim, Baxter, Nihon Kohden
and Quintiles. He currently heads Consulting and Business
Development for FTI and may be contacted at: 800-326-6480,
714-258-1800 or via RHecker@franek.com.
2002 Copyright Franek Technologies,
Inc.
13821 Newport Avenue, Suite
100
Tustin, CA 92780-7803 USA
1“Laboratory
Management Contingency Planning – The New Paradigm”:
MedPro Month Volume X1, Number 12, December 2001 – IHS
Health Group
2“Laboratory Management
Contingency Planning – Environmental Assessment”:
JALA Volume 7 Number 1, February 2002 - The Association for
Laboratory Automation
3“Reducing Power Factor
Costs”, US DOE, Office of Industrial Technology, 1966
4“Energy Management
Handbook”: Turner, Wayne C. - Fairmont Press Inc., 1993
5Danaher Corporation, Electrical
Test and Measurement – Fluke Electrical Power, 2001
6“A New Approach to
Load Balancing and Power Factor Correction in Power Distribution
System" A. Ghosh and A. Joshi, IEEE Transactions on Power
Delivery, Volume 15, Number 04, October 2000
7“Power Factor and
Harmonics” – Keith H. Sueker, Robicon Corporation,
Bulletin 720-008, 1987
8“Reducing Power Factor
Cost,” Technology Update – US DOE, Bonneville Power
Administration, April 1991
9“Energy Realities:
Rates of Consumption and Future Options” and “CEIDS
– The Self Healing, Digital-Quality Super Highway”
EPRI address to the US House of Representatives, Subcommittee
on Science Hearing May 3, 2001
10IEEE/IEC Standard 62040-3
Categories for Uninterruptible Power Systems (UPS) –
Category 3 Double Conversion “Rectifier /Charger (Dual
Conversion On-line)”
11Source: Franek Technologies,
Inc.
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