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STEMS
EMS
The Next Generation in Band-Pass Filters.
Engineers
have developed a variety of electronic filters to reduce
the effects of unwanted signals (commonly referred to as
‘noise’) on the desired signal. Like fluid filters,
electronic filters can be made from a variety of materials,
typically including a combination of operational amplifiers,
capacitors, and/or varistors. These electronic filters are
classified as high-pass, low-pass, and band-pass filters.
High-pass filters block out low-frequency noise, and are
often used to prevent low-frequency signals, such as ham
radio broadcasts, from interfering with and distorting higher-frequency
signals, such as TV signals. Low-pass filters block out
high-frequency noise and can be used to minimize the effects
of harmonics in inductive motors. Band-pass filters behave
as a combination of high-pass and low-pass filters and only
allow certain ranges of signal frequency to pass through
them.
HOW
STEMS WORKS:
STEMS
is a highly sophisticated band-pass filter that blocks distortions
in electrical power above and below normal signal range.
STEMS blocks out harmonics, power spikes
and surges.
STEMS cleans up utility-supplied power
to make it better fit the form of a 60-cycle sine wave,
forcing current and voltage to conform to that sine wave
as well, the ideal design condition for American AC motors.
As a result, motors run more smoothly at lower temperatures,
work more efficiently and require less power from the utility.
Put
another way, the band-pass effect of a STEMS added to your
electrical circuitry will "clean up" your AC power.
This creates an ideal operating environment for your equipment,
which reduces equipment wear and increases equipment life.
This increases power factor, reduces kVAR, amp draw and
most importantly, KWH usage.
Remember, you are billed for KWH. Reducing your KWH reduces
your electric bills.
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ABOUT HOW STEMS WORKS
In
order to understand how a STEMS unit works and why it can
reduce your electric utility bill, you need to understand
some electrical terminology.
Readers
generally fall into two groups, much like a person who buys
a new computer. Some don’t care to spend the time
to read the manual or acquire an in-depth knowledge of how
it works. They just want to turn it on and have it start
working. Others like to get a deeper understanding of the
product before turning it on. The following information
is addressed to this group. It is intended to give you a
better understanding of some of the factors involved and
how the STEMS unit addresses them.
AMPERES
(Sometimes referred to as amps) – This is an indication
of the flow of electric current into a circuit (sometimes
referred to as the rate of electron flow). This includes
both borrowed and used power.
EFFICIENCY – A measure of how well
a device converts the power that is purchased into useful
work.
Resistive
devices convert almost all of the power used to a useful
form of energy, such as the heat energy created by an electric
heater or stove element or the light energy created by a
light bulb. In each case, the losses are very small. Resistive
devices are considered to be 100% efficient.
Inductive
elements are magnetic devices such as solenoid coils, motor
windings, transformers, windings, fluorescent lamp ballasts,
microwave ovens, and similar equipment that have magnetic
components as part of their design. In inductive devices,
such as electric motors, not all of the purchased power
is converted into usable energy. A certain portion is lost
and is not recoverable because it is expended in the losses
associated with operating the device.
Aside
from so-called friction losses, and the inherent losses
between the rotor and stator, there are other “loss
factors” that must be considered. There are losses
associated with passing cooling air through the motor. There
are also losses from motor surges associated with voltage
spikes. Copper and Iron losses are an important consideration,
as well. In an energy efficient motor, using a design that
employs better grades of materials reduces the losses. Anything
that reduces losses will increase efficiency.
KWH
– Kilowatt Hour: The basic unit of measure
of a residential, commercial and residential electric bill.
This is a measure of the amount of power that is delivered.
In many respects, the Kilowatt Hour could
be compared to a ton of coal, a cubic foot of natural gas,
or a gallon of gasoline; in that way, it is a basic energy
unit.
KVA
– is total apparent power, measured in kilovolt amps.
This unit is used instead of using the term kilowatt, when
engineers are discussing AC-powered motorized equipment.
POWER
FACTOR – The amount of real power that is
used, divided by the total amount of power both borrowed
and used.
Perhaps
the greatest confusion arises due to the fact that early
in our science education, we were told that the formula
for Watts was Amps times Volts.
This formula, Watts = Amps times Volts, is true for direct
current circuits.
It also works on resistive AC loads, such as incandescent
light bulbs, and electric range heating elements.
However,
when the loads involve a characteristic called inductance,
the formula has to be altered to include a new term called
power factor. Thus, the new formula for single-phase loads
becomes: Watts equal Amps times Volts times Power Factor.
The new term power factor is always involved in applications
where AC power is used and inductive magnetic elements exist
in the circuit. Power factor is expressed as a decimal or
as a percentage value.
Values
for power factor will range from zero to 1.0. In the case
of electric heating elements, incandescent light bulbs and
similar resistive power, the power factor is assumed to
be 1.0. Power factor can be expressed as a decimal or as
a percentage value, but it is usually listed on a utility
bill as a decimal.
In
the case of electric motors, the power factor is variable
and changes with the amount of load that is applied to the
motor, the quality of the materials used, and the “cleanness”
of the electrical power supplied. Thus a motor running on
a work bench, with no load applied to the shaft, will have
a low power factor, perhaps .10 (10%). A motor running at
full load, connected to a pump or a fan might have a high
power factor perhaps .88 (88%).
The
term “Power Factor” is difficult to understand.
However, the following illustration might help. Utilities
have to size their transformers and distribution equipment
based on the amount of amperes that are going to be drawn
by the customer. Some of these amperes are “borrowed”
to magnetize inductive loads within the plant. This “borrowed”
power is later returned to the utility company without having
been used. This borrowing and returning goes on at a rate
of 60 times a second (the frequency of a 60 cycle power
system). The borrowed power, as previously mentioned, is
used to magnetize such things as electric motors; transformers,
fluorescent light ballast, and may other kinds of magnetic
loads within a plant. In addition to the “borrowed”
power, there is so-called real power. This is the power
that is used to produce heat from heating elements, light
from incandescent bulbs, and to drive the shaft on motors.
Power
Factor is a measure of the relative amounts of borrowed
versus real power that is being used within the plant or
piece of equipment.
REACTIVE
POWER is the non-working power, required to operate
the device (measured in kilovolt-amperes-reactive, kVAR).
The user is billed for this power, which is the area where
the STEMS device provides the most benefit.
REAL
POWER – The power actually used to operate
the device, measured in kilowatts, kW.
The
Kilowatt Hour is not directly related to
amperes, and at no place on an electric bill will you find
any reference to the amperes that have been utilized. It
is vitally important to note this distinction. You are billed
for kilowatt-hours: you do not necessarily pay for amperes.
WHY
IMPROVE YOUR POWER FACTOR? – There are two
primary reasons for improving your power factor. First,
you will save money by reducing your power utility bill.
Second, you will reduce the equipment wear and waste heat
of inductive loads, thereby increasing the service lives
of your equipment, which will lower your overall operating
costs. Your goal should be to achieve the highest possible
power factor in all of your equipment.
Some
of the other benefits of power factor improvement include:
