HPS High Efficiency
Transformers
October 2012
Locations
Hammond Power Solutions is North America’s largest and
broadest manufacturer of dry-type transformers:
Warehouses are located in CA, FL, IL, NC, TX, WA, WI (USA) & BC, ON, QB (Canada)
Contact & Technical Information
Canada:
Tel: 519-822-2441 / Fax: 519-822-9701
cdnquotes@hammondpowersolutions.com
United States:
Tel: 608-356-3921 / Fax: 608-355-7623)
usquotes@hammondpowersolutions.com
Efficiency: Why A Transformer is
Different
Judging the savings of an efficient
transformer is different than other
products for three major reasons.
Efficiency: Why A Transformers is
Different
Transformers are already highly efficient:
• 97.0%-99.5% efficiency at 35% average load for TP1.
• Improvements in efficiency are measured in 10ths
of a percentage.
A transformer will last for 25-30 years
with little maintenance.
• An improvement in efficiency will pay dividends
for decades.
A transformer will not be shut off.
• Even small improvements result in large dollar
savings when measured 24/7 every day of the
year.
Transformer Efficiency Potential
Many studies were made in the 1990’s on typical loading and annual losses
–
–
–
E Source-1995
ORNL-1997
Cadmus Group-DOE-1999
E-Source - 1995
ORNL - 1997
CADMUS - 1999
Annual Losses
60-80 billion kWh (Based on discussions
with researches from ORNL)
80 billion kWh
17 billion kWh (Energy savings for low
voltage only)
Annual Savings
Potential
$1 billion per year (1-3 cents per square
foot of building space)
330-400 million kWh
350 million kWh
Load Factor
35%
35%
16%
Opportunities/Savings Potential of Dry-Type Transformers.
Sources: Barnes et al. 1997: E-Source 1995; Korn et al. 1999
Transformer Efficiency Potential
Many studies were made in the 1990’s on typical loading and annual losses
–
–
–
E Source-1995
ORNL-1997
Cadmus Group-DOE-1999
E-Source - 1995
ORNL - 1997
CADMUS - 1999
Annual Losses
60-80 billion kWh (Based on discussions
with researches from ORNL)
80 billion kWh
17 billion kWh (Energy savings for low
voltage only)
Annual Savings
Potential
$1 billion per year (1-3 cents per square
foot of building space)
330-400 million kWh
350 million kWh
Load Factor
35%
35%
16%
Opportunities/Savings Potential of Dry-Type Transformers.
Sources: Barnes et al. 1997: E-Source 1995; Korn et al. 1999
Efficiency Timeline
2006: The
2005: The
1996:
1992:
DOE
starts studies
for efficiency
evaluation.
DOE
publishes
Distribution
Transformer efficiency
standard TP1
for voluntary
use by Industry
2002: NEMA
developed
NEMA TP-12002: At this
point, NEMA’s
work was only
a guideline.
Energy Policy
Act of 2005
(Epact 2005)
specified that
all low-voltage
dry-type
transformers
manufactured
on or after Jan.
1, 2007 must
be Class I
Efficiency Level
as defined by
NEMA in TP-12002 a law.
EPA
suspended the
Energy Star
program for
distribution
transformers
because the
mandated TP1
models met the
current criteria.
EPA stated that
energy
efficiency
improvements
were not cost
effective at the
time it
suspended the
program.
2007: DOE
established
minimum
efficiency
values for most
dry type, 600
volt class
distribution
transformers
through 1000
kVA in its 10
CFR 431
Subpart K on
Jan. 1, 2007.
Canada has
similar C802.2
requirements.
2009:
Environmental
groups filed a
lawsuit that the
DOE should
require more
efficient
designs. The
Court allowed
the DOE
standards but
also required
the assessed
the standards
to be reviewed
and increased
if needed at a
later date.
2012: If the
2010: DOE
established
minimum
efficiency
values for most
oil and dry type
transformers
through 2500
kVA in its 10
CFR 431
Subpart K on
Jan. 1, 2007.
Canada has
similar
SOR/94-651
requirements.
2011: NEMA
announced the
Premium
Efficiency mark
on transformers
which were
30% more
efficient than
NEMA TP-1
2011: The
DOE proposed
rulemaking to
review and
amend the
current
standards in
effect for
distribution
transformers.
proposed
rulemaking is
determined to
be justified, the
DOE must
provide a final
rule by Dec. 1,
2012. If it goes
into effect, the
DOE would
probably
provide 2-3
years for
transformer
manufactures
and the supply
channel to
implement.
NEMA TP1/C802.2 Terms
DOE 10 CFR Part 431:
The actual legislation
which requires TP1
Efficiency levels for 600
volt class dry type
transformers.
NEMA Premium – New
NEMA specification
highlight 600 volt class
efficiencies 30% higher
than TP1.
TP3 – Designates how
a transformer’s
nameplate designates
TP1
TP2 – Designates how a
transformer’s efficiency is
measure (linear load and
no-load losses at 35%
load for 600 Volt class,
50% load for medium
voltage.
C802.2 – The Canadian
equivalent to DOE 10
CFR Part 431 which also
currently has the same
efficiency levels for 600
volt class dry type
transformers.
SOR/94-651 –
Canadian Energy
Efficiency Act similar to
DOE 10 CFR Part 431.
TP1 – Efficiency levels
promoted by NEMA for
600 Volt class and
medium voltage
transformers. US and
Canada have higher
efficiency levels for
medium voltage
transformers than TP1
tables.
Standard vs. NEMA TP1/C802.2
The laws in North America state that all dry-type distribution transformers manufactured
after January 1, 2007 in the US and January 1, 2005 in Canada, must meet the minimum
energy efficiency standards outlined by NEMA TP-1-2002 (US) and C802.2 (Canada).
The range of product covered by these standards are:
Voltage Rating
Dry-Type Rating
1
Primary Voltage
Secondary Voltage
Single Phase
Three Phase
U.S. (TP1) 3
600 Volts and Below
600 Volts and Below
15-833 kVA
15-333 kVA
Canada (C802.2) 1
35 kV and Below
4160 Volt and Below 2
15-833 kVA
15-7500 kVA
For C802.2 the low voltage 1.2 kV class kVA range covers 15-333 kVA single phase and 15-1000 kVA three phase.
2
4160 Volt (30 kV BIL) and below.
3
U.S. TP1 is regulated by DOE 10, CFR Part 431
Standard vs. NEMA TP1/C802.2
Standard vs. NEMA TP1/C802.2
Common DOE 10
CFR Part 431
exceptions
include.
• Drive Isolation Transformers (Required to meet C802.2 in
Canada)
• Auto-Transformers
• Rectifier Transformers
• Sealed Transformers (Potted, Enclosed NEMA 4, 4X and 12)
• Tap range greater than 20%.
• Ferro-Resonant
• Impedance less than 1% or greater than 8%
• UPS transformers
• Welding Transformers
• Marine applications not connected to the U.S. Power Grid.
• Transformers exported outside of the U.S. or Canada.
• Transformers to be installed as a component on machinery
and/or powers a load not covered by EPACT requirements.
• Testing Transformer
• Transformer is not connected to the U.S. or Canadian power
grid (self generated power).
NEMA TP1 vs. Premium Efficiency
Pending Legislation
The DOE is reviewing NOPR, 10 CFR 430. It has analyzed three low-voltage
dry-type transformer sizes—25 kVA, 75 kVA, and 300 kVA.
Analysis is based on different efficiency levels, as well as the associated
manufacturing, operating, and lifecycle costs. The proposed efficiencies for
comparison are the existing NEMA TP-1-2002 levels;
• Trial Standard Level 1 (TSL-1) - ID’d as Efficiency Level 2 (EL-2)
• NEMA Premium Efficiency (EL-3).
• The terms the DOE uses are Trial Standard Level (TSL), Efficiency Level (EL)
and Candidate Standard Level (CSL)
• The proposed rule is identified by the TSL number (see Table)
The current DOE economic analysis is available on its website
(www1.eere.energy.gov) and included as part of the proposed rule.
• DOE analysis indicates between a 4-5-year payback (design line 7: 75 kVA
transformer) and an 8-year payback (design line 8: 300k VA transformer).
The intent is to extrapolate this data across the board to all sizes of dry-type
transformers, and it appears to somewhat justify transformer cost.
NEMA Premium vs. CSL-3
Efficiency
Candidate Standard Level (CSL) is a term used in the
DOE efficiency evaluation process for transformers.
• The number (1-5) following the term CSL is based on the range of
transformer efficiency levels considered.
• The levels were determined based on efficiency without consideration of
material, availability or cost and current models in production.
The DOE has five levels equally spaced.
• CSL1 is equal to NEMA TP1
• CSL5 equal to the highest calculated efficiency value.
• As part of the simplification process for analysis, the DOE chose three
representative transformer sizes for evaluation.
For LV dry transformers three-phase, only the 75 kVA, and
300 kVA models where chosen as designs to evaluate.
• Other kVA efficiencies can be extrapolated using TL1 = TL0 × (S1 / S0)0.75.
NEMA Premium vs. CSL-3
Efficiency
The efficiencies were originally listed as ‘Candidate Standard
Levels (CSL)’.
As the standard matured through it’s cycle of ‘ANOPR -> NOPR ->
Final Rule’, the efficiencies became based on actual efficiency
measurements from ‘Design Line Representative Units’,
• The efficiency levels became known as ‘Trial Standard Levels’ (TSL).
• TSL-1 is equal to TP1.
• Higher TSL levels were based on the most efficient designs from the engineering
analysis” (72 Fed. Reg 58199, October 12, 2007, Final Rule).
CSL-3 originally corresponded to efficiency levels about 30% better
than TP1
• TSL-3 levels tend to be about 35% better than TP1.
NEMA has responded to the industry need for a high efficiency low
voltage transformer standard with the Premium Transformer
Program.
• NEMA Premium transformers will provide 30% efficiency improvement over EPACT
2005 for all standard LV transformer sizes.
• The NEMA Premium program supplements the industry standards NEMA TP1, TP2 and
TP3 to provide the industry with the next generation of high efficiency requirements.
Types of Losses
Load is important to determine efficiency and calculating losses. 600
Volt Class units are tested using a resistive 35% load with a sinusoidal
input per TP2. Medium voltage is tested at a 50% load.
No-load losses (Core)
occur in the core, are
mainly caused by
hysteresis and eddy
currents and are
independent of the load.
No-Load Test: With the
secondary winding open
circuited, rated voltage at
rated frequency is applied
to the primary winding,
and the power input is
equal to the no-load loss.
Load losses (I2R) vary by
the loading and occur in
the coils. Load Loss Test:
With the secondary shortcircuited, reduced voltage
is applied to the primary
sufficient to drive rated
current through the
windings, and the power
input is equal to the load
loss.
Types of Losses
Load losses increase with the square of the load (I2R). There is a
concern that load losses above 35% load can impact system’s
capacity, costs and reliability.
Transformer loads can vary from
virtually ‘no-load’ conditions to very
high load factors above 90% instantly.
No minimum No-Load Loss/Load Loss
tables exist within US or Canadian
standards to show compliance with a
particular CSL/TSL level; only
minimum efficiency.
Types of Losses
Manufacturers typically reduce the no-load core losses
when transformer efficiency is measured at 35% load.
• This is more economical than trying to reduce conductor losses.
• AL and CU coils have similar efficiency.
Manufactures use a variety of techniques for no-load
losses:
• Use thinner and/or grain oriented core steel
• Gapped cores, mitered cores and step-lap core construction.
• Low Temperature Rise transformers may be less efficient at lower loads
where transformers often operate because of their larger cores.
Specifications should specify an efficiency level, let
the manufacturer determine the best design method
to achieve it.
Outside Affects on Efficiency
Harmonics
• Will lower efficiency but they can change and their
effects are difficult to accurately calculate.
• Poor power quality can result from both non-linear
loads and poor overall system quality.
Power Factor
• Low levels will cause additional losses.
• Voltage Levels
Higher or lower voltages that are not
compensated by the taps can cause
additional losses.
Outside Affects on Efficiency
The power factor is the ratio between the
active power (W) and the apparent power
(VA).
• If the current and voltage curves are not aligned, efficiency is
diminished and apparent power exceeds active or true power.
• In an inductive system, the voltage leads the current curve.
• In a capacitive system, the current leads the voltage curve.
• Historically, when speaking of power factor, we were actually
referring to the displacement factor only.
Due to the increase in non-linear loads, we have had to take
into account the effect of harmonics in electrical systems and
include the effect of the distortion factor. Power factor is now
defined as follows:
PFtot = Fd x Fdist
where PFtot = total power factor
Fd (displacement factor) as defined above
Fdist (distortion factor) = fundamental current
RMS current
Outside Affects on Efficiency
Distortion Factor = The fundamental current divided by the RMS
current (current measured with a true RMS clamp-on ammeter). There
are two elements which combine to reduce total power factor:
• Inductive or capacitive loads which affect the displacement factor
• Harmonic currents of the non-linear loads which affect the distortion factor.
Reducing the level of harmonic currents improves the system’s total
power factor.
• As utilities measure the total power factor, we have to check the value of both displacement factor and
distortion factor if total power factor is to be corrected.
• Measuring instruments now provide the value of both of these factors (or it is possible to calculate them).
Outside Affects on Efficiency
Impedance:
Leakage Flux:
• The percentage (%)
impedance is the
voltage drop at full load
due to the winding
resistance and leakage
reactance.
• Impedance is shown as
a percentage(%) of the
rated voltage.
• Transformers typically
have impedances of 3%
to 6%.
•Function of winding turns
and the area and length of
the leakage flux path.
•Vary the volts per turn and
shape of the windings to
control impedance.
•Wire Size is a fixed
function for heat rise and
efficiency and isn’t varied.
•Actual impedance may
vary from calculated due to
variations in the shape of
the coils and difficulty in
estimating the actual
leakage reactance through
modeling.
The most economical
arrangement of core
and windings leads to
a 'natural' value of
impedance
determined by the
leakage flux.
Efficiency vs.
Impedance
•Impedance and efficiency
have little correlation since
wire size and therefore
conductor losses are
usually fixed by the
conductor carrying
capacity.
•DOE efficiency levels
require minimum
efficiencies for
transformers ranging from
1% to 8% impedance.
Measuring Efficiency
Measuring transformer efficiency is challenging. Generally transformer
efficiency levels are measured using the open and short circuit tests.
• The open circuit method measures the No-load core losses.
• The short circuit tests measures the I2R load conductor losses.
When transformers are in operation, measuring transformer efficiency
is difficult:
• Loads will have varying power factors, non-linear components.
• Calculations require highly accurate and calibrated power meters and measuring
equipment.
Modern DOE mandated efficiency levels are:
• Measured under a linear load at 35% for 600 volt class units
• Measured under a linear load at 50% load for medium voltage units.
• This load curve on a highly variable commercial or industrial load is difficult to simulate and
measure accurately.
Efficiency Testing Requirements
There is little
or no benefit
to measure
transformer
efficiency in
the field for
modern units
other than to
add cost to a
project.
• Load (conductor) and No-Load (core) losses
should are stable.
• HPS uses industry standard testing methods
and calibrated testing equipment at factory.
• Efficiency levels can be recorded for less
money at the factory.
• Beware - PT’s and CT’s are not recommended
to be permanently installed on 600 volt class
transformers for the sole purpose of verifying
transformer efficiency. These devices provide
additional losses, costs and failure modes.
Calculating Savings
When
Calculating
Energy
Savings:
• Know what you are comparing. Existing
transformer efficiency is not recorded on the
nameplate.
• Efficiency varies by load, power quality,
manufacturer and when the unit was
manufactured.
• There is no national database for efficiency data.
• HPS uses the base efficiency levels of our
standard efficiency units in 2007 when calculating
payback.
• Beware, a manufacturer using lower standard
efficiency levels will show a larger savings even
though each manufacturer’s base efficiency curve
for the new units is the same.
Information to Calculate Efficiency
Pre-TP1 transformers don’t have nameplate efficiency levels.
• TP1 600V class has efficiency at 35% load, other loads vary by manufacturer.
As a result, existing transformer efficiency levels are typically
estimated.
• HPS uses efficiency levels from our current and past units to estimate payback for other
manufacturers.
To do an efficiency analysis, the following information will be required:
• Transformer kVA
• Primary and secondary voltage and if above 600V class, BIL level.
• Typical load profiles (percent of load at hours per day or year). Load profiles don’t have
to be exact, HPS Tool Box for instance uses 0%, 15%, 25%, 35%, 50%, 65%, 75% and
100%.
• Estimated load profiles are often used based on the building, i.e. a hospital is used
24/7/365 while a school might used 10/5/200.
• While harmonics can play a big part in transformer efficiency, they can vary extensively
minute by minute. Typically savings is estimated without their inclusion with the assumption
that they have an equivalent effect on both the existing and new transformers so the same
amount of energy is saved.
Payback vs. Savings
Many manufacturers focus on savings, a high efficiency
transformer will save x-dollars over a year of use.
• With a large number of choices for energy saving devices, most
customers will focus on comparing paybacks which typically factors in
what the overall installed cost of the device is minus rebates and then
divided by the yearly savings.
Typical high efficiency transformer installations will have
paybacks of 3-10 years. Major factors are
• Transformer Efficiency
• Transformer Costs
• Installation Costs
• New construction - installation costs typically aren’t considered.
• Installation costs may not be considered for end-of-life replacements.
End-of-life replacements might actually give credit for savings from uptime.
• Electricity costs and demand charges
• Site Loading
• Rebates
ASHRAE Guidelines
ANSI/ASHRAE/IESNA Addenda d, o, x, aa, ab, ae, at, au, and ba to
ANSI/ASHRAE/IESNA Standard 90.1-2007
8.4.2 Low Voltage Dry-Type Distribution Transformers. Low voltage dry-type transformers shall
comply with the provisions of the Energy Policy Act of 2005 where applicable,as shown in Table 8.1.
Leadership in Energy and
Environmental Design - LEED’s
Some manufactures have implied there is an assigned LEED’s credit for Premium Efficiency
Transformers, there is not. There are several areas of LEED credits that the transformer can play a
role in achieving.
Premium energy efficient transformer can help client achieve a LEED’s credit if they
reach an energy savings associated with their overall predicted use of energy relative
to a benchmark.
LEED requires monitoring of the entire system to achieve efficiency this credit. Specific
monitoring on a transformer is probably redundant and may actually compromise the long
term integrity of the transformer if the monitoring sensors fail.
Packaging used in the transformer doe not need to be 50% recyclable. The referenced credit
specifically exempts electrical components which can not be included in the recycling
calculations.
ISO 14001 certification in the transformer manufacturing facility is not need. ISO 14001 is an
environmental standard that has nothing to do with transformers and is not a credit item for
LEED.
End of Life / MTBF
An opportunity for retro-fits is to replace existing units before they fail.
Transformers failures are very expensive because of lost commercial time.
• Repair time exceeds many temporary power devices such as UPS.
• Long term backup power often runs through the transformer.
• Transformers are big and heavy, emergency replacement is typically more expensive and time
consuming than other electrical components.
Electrical code typically requires that transformers are oversized as are
other electrical components.
• DOE measures 600 volt class transformers at 35% load.
• Typically a transformer will last 25-30 years.
• Combinations of extended high load factors, high ambient temperatures and harmonics can
reduce the life of a transformer’s insulation components and cause failures much earlier.
Signs of failure would include:
• Discoloration (clear to yellow, yellow to brown) and/or cracking of the insulation.
• Lower megger values could indicate insulation damage.
• Excessive heat, harmonics, high voltage spikes (including megger tests), conductive dust and
moisture can significantly reduce the expected lifetime of a transformer.
In-Rush Concerns
Now, consider both fault and overload damage
protection: Which breaker should protect the
transformer?
• Ideally, it’s the primary breaker, but either or both breakers could
be for the protection of the transformer.
• The primary is ideal because it would protect from any fault that
occurs between the secondary conductors and the primary
breaker.
• Although it is ideal, accommodating the inrush and protecting the
transformer with just the primary breaker can create a challenge.
Back-feeding a transformer can significantly
increase its inrush profile.
• This occurs because the secondary coil’s closer proximity to the
core results in higher inrush when it is energized first.
Inrush is highly dependent on how long a
transformer is de-energized and what was the
voltage phase-angle was at de-energization and
re-energization for short duration faults.
• The quicker the fault and the higher the deviation in phase angle
at de- and re-energization the higher the current inrush.
HPS Toolbox – Calculating Payback
HPS Toolbox – Calculating Payback
HPS Toolbox – Calculating Payback
HPS Toolbox – Calculating Payback
In this case
we will
enter a
custom
application
for a
hospital
type
building that
operates at
365 days.
• Calculate for 10 hours
@ 50% load per day.
• Calculate for 14 hours
@ 25% load per day.
• Sampling of 75, 112.5
and 300 kVA units.
• $0.12/kwHr
HPS Toolbox – Calculating Payback
The efficiency, losses and savings are
calculated from actual HPS products
including older non-TP1 units.
Losses will vary slightly between general
purpose, K-rated and harmonic mitigating
units because of slight differences in
design resulting in different efficiencies
outside of 35%.
Premium efficiency units compare their
savings to both older non-TP1 units and
TP1 units.
HPS Toolbox – Calculating Payback
Energy consumption is strictly from the
transformers and does not take into
account additional savings that could occur
from lower demand charges, less cooling,
etc.
This program is designed to provide quick,
general estimates to transformer payback
while providing the raw kWh data for use
with ESCO’s overall programing.
Information can also be used for things
such as LEED’s studies.
Calculate Payback
Case Study:
Commercial Office Building operates 10 Hours per day, 5 days a week @ 65% load. It
operates the remaining time at 15% load. $0.12/kW Hour.
TP1 vs. Standard
$477.38
$724.35
$1,098.48
Savings per Year
Premium vs. Standard
$629.08
$974.12
$1,557.39
Premium vs. TP1
$151.70
$249.77
$459.10
Substitute
Premium vs. TP1
$151.70
$249.77
$459.10
75 kVA Base Cost
Installation Cost
1600
1400
3400
1400
3400
1400
3400
0
150 kVA Base Cost
Installation Cost
2700
1800
5200
1800
5200
1800
5200
0
300 kVA Base Cost
Installation Cost
5400
2000
11000
2000
11000
2000
11000
0
6.3
6.2
6.7
7.6
7.2
8.3
21.1
17.2
16.6
11.9
10.0
12.2
$0.12/ kwHr
75 kVA
150 kVA
300 kVA
75 kVA Payback(yr)
150 kVA Payback(yr)
300 kVA Payback(yr)
Calculate Payback
Case Study:
Hospital Building operates 10 Hours per day, 7 days a week @ 65% load. It operates
the remaining time at 35% load. $0.12/kW Hour.
Savings per Year
$0.12/ kwHr
75 kVA
150 kVA
300 kVA
75 kVA Base Cost
Installation Cost
150 kVA Base Cost
Installation Cost
300 kVA Base Cost
Installation Cost
75 kVA Payback(yr)
150 kVA Payback(yr)
300 kVA Payback(yr)
Substitute
TP1 vs. Standard
$583.98
$908.20
$1,403.68
Premium vs. Standard
$790.90
$1,276.13
$1,988.94
Premium vs. TP1
$206.93
$367.94
$585.27
Premium vs. TP1
$206.93
$367.94
$585.77
1600
1400
2700
1800
5400
2000
3400
1400
5200
1800
11000
2000
3400
1400
5200
1800
11000
2000
3400
0
5200
0
11000
0
5.1
5.0
5.3
6.1
5.5
6.5
15.5
11.7
13.0
8.7
6.8
9.6
Downsizing Transformer kVA
In many retrofit situations, the load has been reduced from what it was originally designed for. An
example is an old lighting system originally designed for incandescent or fluorescent lights that is now
running LED’s. It may be possible to substitute a smaller transformer for the original unit. Please note
that overcurrent protection will probably have to be resized for the smaller transformer and national and
local codes may require to the transformer to be a minimum size.
Operation Cost per Year Downsizing 300 kVA to 225 kVA or 150 kVA
$0.12/ kwHr
150 kVA
Standard
$2,105.52
TP1
$1,197.36
Premium
$829.44
150 kVA kWHr's/year
225 kVA
17,546
$2,803.20
9,978
$1,554.96
6,912
$1,156.32
225 kVA kWHr's/year
300 kVA
23,360
$3,372.84
12,958
$1,969.08
9,636
$1,383.84
300 kVA kWHr's/year
28,107
16,409
11,532
2700
1800
3900
1900
5400
2000
TP1 vs. Stud
2.1
3.1
5.3
5200
1800
7600
1900
11000
2000
Premium vs. Std.
2.8
4.3
6.5
5200
1800
7600
1900
11000
2000
Premium vs. TP1
0.0
2.5
13.0
150 kVA Base Cost
Installation Cost
225 kVA Base Cost
Installation Cost
300 kVA Base Cost
Installation Cost
150 kVA Payback(yr)
225 kVA Payback(yr)
300 kVA Payback(yr)
Upgrade to HMT or K-Rated
Non-linear loads are the fastest growing phenomenon in the electrical
industry
• It has changed the way we design, install and calculate losses for energy conservation
• New approach in design for TP1 transformers under Non-Linear Load Loss (NLL) and
Phase Shifting installation techniques reclaims more energy under those types of loads.
Many projects specify general purpose transformers not
designed to operate non-linear loads which produce harmonics.
• Harmonics cause the transformer’s equivalent full load capacity to be reduced.
Harmonics are typically odd (3rd, 5th, 7th, etc.).
• Single-phase sources (120V DC power supplies) produce the most current at the 3rd
harmonic.
• Three-phase loads (VFD’s, large DC Power supplies) produce the most current at the 5th
harmonic and don’t produce 3rd harmonics.
• Higher order harmonics produce more heat per amp than lower order harmonics, roughly
equivalent to the square of the harmonic
Upgrade to K-Rated
K-Rated transformers have three main differences over general
purpose transformers:
• Handles additional heat generated by the harmonics with no de-rating.
• K-rated has 200% rated neutral because of the potential for high neutral
currents (up to 173%), exceeds a general purpose’s 125% design.
• K-rated has an electrostatic shield between the primary and secondary.
K-rated transformers must meet the same TP1 efficiency levels
at 35% linear load that general purpose units have to meet.
• Efficiency measured without harmonics at sinusoid.
K-Rating Rule of thumb:
• If less than half of a transformer’s load is Non-Linear, use K=4.
• Otherwise use K=13.
• Size critical loads at K=20.
Upgrade Further to an HMT
Harmonic mitigating transformer are K-rated
transformers designed with a Zig-Zag secondary
winding.
• The Zig-Zag winding allows some cancellation of triplen (3rd) harmonics within
the transformer’s windings increasing the system’s overall power quality and
efficiency.
• Since a Zig-Zag transformer may eliminate the need for a filter, it would
conceivably eliminate the additional energy lost in the components of a
traditional LC filter network while offering a longer lasting device.
Upgrade Further to an HMT
The main benefits to K-rated transformers is increased uptime because the unit is designed to handle the harmonics
up to the K-rating and not overheat.
• K-Rated units don’t provide additional power quality over a similar shielded general
purpose unit.
Harmonic Mitigating Transformers (HMT’s) provide the
additional benefit of harmonics cancellation and improved
power quality.
• HMT’s may provide additional payback by reducing the need, costs and losses for LC
filters on critical loads.
Upgrade Further to an HMT
In addition to canceling the 3rd harmonics in an HMT’s windings, HMT can be bought with either a 30o or 0o
phase shift.
Mixing the phase shifts allows for additional cancellation of higher order harmonics including the 5th at the
point of common coupling.
The point of common coupling is typically where a larger transformer feeds two or more smaller units.
Cancellation minimizes the voltage distortion for better Power Quality
Typical DIT Phase Shift Application
Δ-Y
Service Entrance transformer
where 5th and 7th Harmonics
experience mitigation through
30o and 0o phase shift of
individual DIT’s and HMT’s.
Alternate DIT’s/HMT’s between 30o and
0o phase shift trying to balance total HP.
DIT’s/
HMT's
30o Phase
Shift
50 Hp
VSD
0o Phase
Shift
100 Hp
VSD
30o Phase
Shift
75 Hp
VSD
30o Phase
Shift
25 Hp
VSD
0o Phase
Shift
50 Hp
VSD
Δ-ϒ
Market Size
Total North American size for Premium Efficiency dry-type 600 Volt Class transformers is estimated to
be about $20,000,000/year.
Approximately 1.2 million distribution transformers sold in the U.S. every year
Channel very focused on ESCO’s and LEED buildings, especially for public buildings.
Tough to get realistic paybacks when energy costs fall below $.10 per kWh.
Some manufacturers offer energy audits and even project financing. Some of the energy audits may
use questionable base efficiency levels for existing standard efficiency transformers.
No states or agencies currently require Premium Efficiency transformers.
Few utilities offer rebates for Premium Efficiency transformers.
• COM ED – Illinois
• Seattle City Light
• Austin Energy
Conclusion
Questions?