In
multiple-unit residential buildings in North America,
lighting and convenience outlets can be connected
line-to-neutral to give the 120V utilization voltage,
and high-power loads such as cooking equipment, space
heating, water heaters, or air conditioning can be
connected across two phases to give 208V. This
practice is common enough that 208V single-phase
equipment is readily available in North America.
Attempts to use the more common 120/240V equipment
intended for three-wire single-phase distribution will
likely result in poor performance since 240V heating
equipment will only produce 75% of its rating when
operated at 208V.
Where
3 phase at low voltage is otherwise in use, it may
still be split out into single phase service cables
through joints in the power supply network or it may
be delivered to a master distribution breaker panel at
the customer's premises. Connecting an electrical
circuit from one phase to the neutral generally
supplies the country's standard single phase voltage
(120VAC or 230VAC) to the circuit.
The
power transmission grid is organized so that each
phase carries the same magnitude of current out of the
major parts of the power transmission system. The
currents returning from the customers' premises to the
last supply transformer all share the neutral wire,
but the 3 phase system ensures that the sum of the
returning currents is approximately zero. The delta
wiring of the primary side of that supply transformer
means that no neutral is needed in the high voltage
side of the network.
Wiring
Phase-Phase
Wiring
directly
between two phases provides √3 or 173% of the
single-phase voltage (208VAC in US; 400VAC in Europe)
because the out-of-phase waveforms add to provide a
higher peak voltage in the resulting waveform. Such
connection is referred to as a line to line connection
and is usually done with a two pole circuit breaker.
This kind of connection is typically used for high
power appliances, such as (in the US) a 2 kW, 208 volt
baseboard heater.
3 phase
power systems may or may not have a neutral wire. A
neutral wire allows the 3 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).
3
Phase Loads
The
most common class of 3
phase load is the 3
phase electric motor. A common 3 phase induction
motor has a simple design, inherently high starting
torque, and high efficiency. Such 3 phase motors are
applied in industry for 3
phase pumps, fans, blowers, compressors, conveyor
drives, and many other types of motor-driven
equipment. A 3 phase motor is more compact and less
costly than a 1-phase motor of the same voltage class
and rating; also 1-phase AC motors above 10 HP (7.5
kW) are not as efficient and thus not usually
manufactured.
Large
air conditioning equipment (for example, most York
air conditioning units above 2.5 tons (8.8 kW) cooling
capacity) use 3 phase motors for reasons of economy
and efficiency. Read more about 3
phase power loads here.
3
Phase Loads Run on 3 Phase Power Generated on 1 Phase
Power
There
are many places and instances where 1 phase power is
the only type of power that is available, or where the
power company wants to charge tens, or even hundreds
of thousands of dollars to install and supply 3 phase
power. In this situation a quality 3
phase generating phase converter is the easy
choice to be run on 1 phase to power 3 phase equipment
of any type.
Quality
3 phase converters are super efficient and a a good
choice for this use. Click here to read
more about powering
3 phase loads with 3 phase power generated from 1
phase power.
3 Phase
Converters
Often
the advantages of 3 phase motors, and other 3 phase
equipment, make it smart and easily worthwhile to
convert single-phase power to generate 3 phase. Small
and large customers, such as residential, rural
businesses, or farm properties may not have access to
a 3 phase supply, or may not want to pay for the extra
cost of a 3 phase service, but may still wish to use 3
phase equipment. Such 3
phase converters may also allow the frequency (see
also frequency
converters) to be varied allowing for different
equipment frequency requirements (50Hz, 60Hz, 400Hz,
etc.) and also for motor speed control (VFDs).
Some locomotives are driven by 3-phase motors with 3
phase converters converted from the incoming supply of
either DC or 1 phase AC.
The
two main types of 1 phase to 3 phase converters are Rotary
Phase Converters and Static
Phase Converters. Click here to read more
about 3
phase converters.
Continue And Read About Additional 3 Phase Power
Details:
3 Phase Contents
