| Single-phase electricity is often used in homes
or business where electricity is mostly used for general purposes
such as lighting and heating.
Typical Features of Single Phase Meters
- Single-phase electric power refers to the distribution of alternating
current in which all the voltages
of the supply vary in unison.
- Standard frequencies of single-phase power systems are either 50
or 60 Hz
- Single phase power availability varies in different countries. For
example, in the UK a single-phase
household supply may be rated 100 Amps to 125 Amps. This may mean that
there is little need for 3
phase electricity in a domestic or small commercial environment.
- LCD display
- Low credit alarming (LED or Buzzer)
- Rate indicator
- Rated voltage 120V, 220 - 240V
- Frequency 50H z, 60Hz
- Current 5A, 10A or 20A
- Maximum current: 60A to 100A
- Starting current 25mA
- Power consumption below 1W
- User interface: Keypad
- Operating temperature -10 to + 65
- Limit temperature -25C to + 70C
- Humidity Operating 95% RH
- IP rating IP52
Power stations supply three-phase electricity which is three times as much electricity
along three wires as can be supplied through two wires, without having
to increase the thickness of the wires.
Large buildings, shopping centers, factories, office blocks, and multiple-unit
apartments generally have three-phase electricity.
The most important class of a three-phase load is the electric motor. Such
motors are applied in industry for pumps, fans, blowers, compressors, conveyor
drives etc. Large air conditioning equipment (units above 8.8 kW cooling
capacity) use three-phase motors for reasons of efficiency and economy.
Resistance type heating such as electric boilers may be connected
to three-phase systems. Electric lighting may also be similarly connected.
These types of loads do not require the revolving magnetic field characteristic
of three-phase motors but take advantage of the higher voltage and power
level usually associated with three-phase distribution.
Large rectifier systems may have three-phase inputs. The resulting DC current
is easier to filter (smooth) than the output of a single-phase rectifier.
Such rectifiers may be used for battery charging, electrolysis processes
such as aluminum production or for operation of DC motors.
Three phase electricity is a smoother form of electricity than single-phase
or two-phase power. It is this more consistent electrical power that allows
machines to run more efficiently and last many years longer. Some applications
are able to work with three-phase power in ways that would not work on
single phase at all.
At the power station, an electrical generator converts mechanical power
into a set of alternating electric currents, one from each electromagnetic
coil or winding of the generator. The currents are sinusoidal functions
of time, all at the same frequency but with different phases. In a three-phase
system the phases are spaced equally, giving a phase separation of 120°.
The frequency is typically 50 Hz in Europe and 60 Hz in the US (see List
of countries http://en.wikipedia.org/wiki/Mains_power_around_the_world).
The currents in each conductor reach their peak instantaneous values sequentially,
not simultaneously; in each cycle of the power frequency, first one, then
the second, then the third current reaches its maximum value. The waveforms
of the three supply conductors are offset from one another in time (delayed
in phase) by one-third of their period.
Three phase has properties that make it very desirable in electric power
systems. Such as: The phase currents tend to cancel one another (summing
to zero in the case of a linear balanced load). This makes it possible
to eliminate the neutral conductor on some lines; Power transfer into a
linear balanced load is constant, which helps to reduce generator and motor
vibrations; Three-phase systems can produce a magnetic field that rotates
in a specified direction, which simplifies the design of electric motors.
Three phase systems may or may not have a neutral wire. A neutral wire
allows the three phase system to use a higher voltage while still supporting
lower voltage single phase appliances. In high voltage distribution situations
it is common not to have a neutral wire as the loads can simply be connected
between phases (phase-phase connection).
A single-phase load may be powered from a three-phase distribution system
either by a connection between a phase and neutral or by connecting the
load between two phases. The load device must be designed for the voltage
in each case.
In places using a 415 volt 3 phase system, the phase-to-neutral voltage
is 240 volts, allowing single-phase lighting to be connected phase-to-neutral
while three-phase motors to be connected to all three phases.
In North America, a typical three-phase system will have 208 volts between
the phases and 120 volts between the phase and neutral. If heating equipment
designed for the 240-volt three-wire single phase system is connected to
two phases of a 208 volt supply, it will only produce 75% of its rated
heating effect. Single-phase motors may have taps to allow their use on
either 208 V or 240 V supplies.
Meters are categorized depending on the volume (flux) of the meter.
Gas Meters are generally measure in cubic meters per hour. Gases are compressible
and change volume when placed under pressure or are heated or cooled. A
volume of gas under one set of pressure and temperature conditions is not
equivalent to the same gas under different conditions.
When gases or liquids are transferred for their energy content, such as
the sale of natural gas, the flow rate may also be expressed in terms of
energy flow, such as GJ/hour or BTU/day. The energy flow rate is the volume
flow rate multiplied by the energy content per unit volume or mass flow
rate multiplied by the energy content per unit mass. Most flow meters will
be used to calculate the volume or mass flow rate which is then adjusted
to the energy flow rate by the use of algorithms to turn the raw flow data
into volumes at base conditions (consisting of specified absolute pressure
Prepaid Gas Meters are typically available with the following features:
- Maximum flux (m3/h): Available in: 2.5, 4.0 or 6.00
- Working pressure: 0.5 to 10 kPa
- Mechanical Counters upto 99999.999
- LCD Display
- Easily replaceable batteries powered at: 4.5v-6v
- Suitable for: Natural Gas, Liquefied Petroleum Gas (LPG)
- Not Suitable for: Water Gas or Coke Oven Gas (Synthesis containing
carbon monoxide and hydrogen)
- Anti-Explosion certified
water meters are mechanical flow meters. Commonly used meters are piston
meters, also known as rotary piston or semi-positive displacement meters.
The piston meter operates on the principle of a piston rotating within
a chamber of known volume. For each rotation, a count for the amount of
liquid is computed.
Various prepaid water meter are available depending on the nominal bore
(NB). NB (nominal bore) also refers to Nominal Pipe Size (NPS). The Nominal
Pipe Size (NPS) is a North American set of standard sizes for pipes used
for high or low pressures and temperatures also indicating the required
The European designation equivalent to NPS is DN (nominal diameter) in
which pipe sizes are measured in millimeters. Based on the pipe size, the
outside diameter (OD) and wall thickness can is obtained by use of reference
tables. See: http://www.engineeringtoolbox.com/commercial-pipe-metric-data-d_1496.html.
Prepaid Water Meters are typically available with the following features:
- Nominal Bore (mm): Available in: 15,20,25
- Maximum flux (m3/h): Available in: 3, 5 or 7
- Water Temperature: 0-40C
- Working pressure: below 0.1MPa
- Mechanical Counters (m3) upto 9999.9999
- LCD Display