- Much has been talked about in recent months regarding
higher electric bills with new digital meters. In order to understand why
this will always be an issue with smart meter technology, we need to look
at the principles used by each type of meters.
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- Oklahoma TV station KOCO report on higher electric bills
almost gets it right
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- Both older electric meters and newer smart meters use
basic magnetic principles. However, which of the two principles they utilize
to sense the magnetic fields created while you consume power is what actually
determines the size of your bill. You will see exactly why your bill will
almost always be higher with a new "smart" electric meter
and why electric companies are so eager to install them.
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- We'll first explore the two magnetic principles used
in detail while leaving out complex equations.
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- OLDER ELECTRIC METERS
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- This type of electric meter works on the eddy current
electrical principle. The silver disk you see protruding through the slot
with black bars is actually made of aluminum. This disk is the visible
part of an electric motor inside the meter known as the rotor. In electrical
motors the rotor is made of a magnetic steel alloy which is required for
the motor to rotate. Yet in older electric meters the rotor is not magnetic.
So how can it work at all?
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- A simple analogy of the eddy current principle is to
think about a calm puddle of water. If you move your finger through the
puddle and keep it moving ripples will continue to form. If you hold your
finger absolutely still, nothing happens and the puddle of water will return
to a mirror-like surface.
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- Aluminum cannot be magnetized, but is affected by any
changing magnetic field passing through it. This characteristic is known
as paramagnetism. Like the puddle, as long as the magnetic field is changing
eddy currents will continue to form in the aluminum and keep forming temporary
magnets.
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- With older electric meters, all power in your home passes
through coils inside the meter. These coils create a magnetic field which
penetrates the aluminum disk, creating eddy currents. These eddy currents
form tiny temporary magnets in the aluminum disk.
- Remember the law of magnets - repelling of like poles
and attraction of unlike poles?
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- Temporary magnets in the aluminum disk formed by eddy
currents have enough force to make the disk to rotate. When the disk rotates
it turns a series of gears behind the meter's faceplate. These move the
hands which show power consumption in kilowatt hours. A 1,000 watt load
running for an hour = 1 kilowatt hour.
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- SMART ELECTRIC METERS
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- In smart meters there are no moving parts and no aluminum
disk to rotate. A simple solid-state sensor works on a principle known
as the hall effect. The stronger the AC field created by the total power
of all loads in the home, the stronger the AC field the sensor detects.
This analog signal is digitized by a convertor and stored in protected
memory, is calibrated in kilowatt hours and appears on the meter's display.
There is a temperature sensor in smart meters to keep the meters calibrated
with temperature changes.
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- In older electric meters, the power line's 60 cycles/second
are averaged together to rotate the disk. The aluminum disk is incapable
of detecting each cycle in the 60 cycles/second. In smart electric meters,
EACH cycle in the 60 cycles/second power consumed is measured. Nothing
is missed.
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- HIGHER READINGS
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- So why do smart meters produce higher readings? Is it
a plot to help flatten your wallet? In fact it's related to what appliances
you have in your home. Mainly, this has to do with electric motors. With
furnace fans and compressors used in refrigeration, there is a very high
starting current. With a small window or table top electric fan starting
current is relatively insignificant. For refrigeration appliances, window
air conditioners, furnace blowers or central air conditioning starting
current is quite high often several times higher than the running
current listed on the nameplate or label.
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- What can be the reason for higher starting current than
running current? In refrigeration appliances, motors must overcome the
refrigerant already in the compressor to start rotation. In the case of
a forced-air furnace fan or central air-conditioning fan, blower wheels
act like large flywheels which must be brought up to speed.
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- In washing machines, starting current is highest when
the spin cycle starts after the wash cycle. It takes many seconds to get
the heavy basket with about 30 gallons of water and heavy laundry up to
full speed before current consumption drops down to what machine's nameplate
shows. A fully loaded basket with water and clothes weighs in well excess
of 100lbs. The washer motor is stalled whenever the washer's timer starts
it, causing the motor to draw almost 20 amps of power.
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- Only after any motor reaches full speed will current
consumption reduce to the values listed on the nameplate or label.
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- National electrical codes require high starting-current
appliances like washing machines, dryers, furnaces etc... to be connected
to their own circuit breaker. This is to insure full power is available
for high starting currents. In engineering terms this is called "in-rush
current."
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- Heating elements in electric ranges, water heaters, clothes
dryers and baseboard electric heaters all draw heavy current when first
turned on. Heating elements are similar to electric motors. A heating element
(and filament light bulbs) are almost a dead short when cold but as soon
as power is applied these begin to heats up. As a heating element or incandescent
lamp gets hotter it draws less current. After a period of time equilibrium
is reached producing no further increase in temperature and power consumption
is stabilized. Older electric meters respond fast enough to heating elements
to add that in-rush current onto the electric bill.
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- To summarize, high starting current motors often draw
very high currents only for a fraction of a second. Due to inertia, older
mechanical disk electric meters cannot respond quick enough to register
large motor starting current. But smart meters have no problem registering
the brief, high power consumption from electric motors as these meters
have no moving parts.
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- Ted Twietmeyer
- tedtw@frontiernet.net
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