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Difference between single phase
and-3-phase E-mail: geno03245w@gmail.com |
 More detail: A three phase motor has a label that specifies phase or 3P, and would not be found in household fans, pump, HVAC or appliances etc, but would be found in business HVAC, or commercial pumping stations etc  Larger image Chart above illustrates the increased power available with 3 phase by comparing horsepower rating for 30-40 amp motor control switches by voltage and number of poles, with 2 pole for single-phase, and 3-pole for 3-phase. At the same voltage, 3-phase delivers more HP per than single-phase. 600 volt is maximum voltage found in ordinary commercial applications, but not every commercial building have or need 600 volt service. 600 volt service must be specified. 600 VAC maximum, when protected by a 30A time delay fuse Resource: Motor switch manual |
All single-phase circuits
require 2 wires to complete circuit. .... unlike commercial 3-phase used for motors etc that require 3 wires to complete circuit. With 120 volt single-phase, it requires 1 Hot and 1 Neutral .... and has efficiency of pedaling bike with 1 leg With 240 volt single-phase, it requires 2 out-of-phase Hot wires, ... and has efficiency of pedaling bike with 2 legs The problem with single-phase ... when both pedals are briefly at top and bottom at same time, the power drops to zero. Commercial 3-phase requires 3 out-of-phase Hot wires, ... and has efficiency of pedaling bike with 3 legs due to higher average power compared with single phase. 3 phase delivers more power than single phase because no two pedals are at the top and bottom at same time, so 3-phase delivers smoother, more continuous power. 3-phase is not available for residential homes because of cost factors, such as heavier materials, more wires, complicated load factors, more transformers, and imbalance issues etc. More detail: "Industrial and commercial 3-phase electric systems differ from residential single-phase: 3-phase power is more complex, but more efficient in motor applications, and large area uses. Higher voltages of 277/480v and 347/600v distribution systems are more efficient, but considerably more dangerous, and should only be maintained and modified by trained and qualified electricians." "In a balanced 3-phase system, the wires can be about 75% the size of conductors (wires) for a single-phase two-wire system of the same KVA (power) rating. This helps offset cost of supplying the third wire required by 3-phase systems." Terminology: KVA is Kilo volt amps, or 1000 volt amps. Since volts x amps = watts (power), the KVA rating means kilowatts and how much power is produced by a motor, transformer, heating element etc. KVA (kilowatt) is a static number for comparing available power, and not to be confused with KWH (kilowatt-hour), which is a measurement of billable wattage (power) consumption over 1 hour of time. Buy: Motor switch MS302 30 amp 2-pole switch MS402 40 amp 2-pole switch MS303 30 amp 3-pole switch MS403 40 amp 3-pole switch 3-pole motor starter Resource: What is 3-phase Transformer theory .pdf What is power factor pdf 3-pole contactors |
 Generator illustration: Larger image |
How are wires out-of-phase from
each other? Out-of-phase means the electrons on one Hot wire are accelerating different directions at any given moment from the electrons on other Hot wire(s). It's important to note that electricity is dynamic and is measured over time. How it happens: Passing a magnet over a coil (winding) of wire causes electrons to move along the wire, creating electricity. This is called electromagnet induction. Inside a power plant generator, the electromagnet rotates in a 360°circle going past 3 coils of wire located exactly 120° apart. The magnet has a south and north pole. As the south pole gets close to the coil, the electrons begin to accelerate one direction on the wire. As the south pole moves away and the north pole approaches the coil, the electrons slow down, momentarily stop, before accelerating back the other direction down the wire. Each time the electrons stop, the voltage drops to zero. The generator spins at 60 times per second (60 cycles, 60 Hz, frequency are common terms) and the direction change happens so quickly that the end user cannot see their light bulbs are actually flickering with the momentary drop to zero volts, and the average voltage is always above zero so the lights stay on. Back and forth the electrons oscillate on each wire, producing what is called alternating current. The magnet arrives at each coil at different times, so the acceleration of electrons on each coil is different, or out of phase. Since there are 3 coils in the generator, 3 Hot wires emerge from the power plant. A single Hot wire is taken from one end of each coil. The other ends of the 3 coils are connected together to form the Neutral wire. (This is called a WYE configuration where amperage on each coil equals amperage on each line, each wire carries the same voltage, and voltage between Hot and Neutral is same on each line.) Each Hot wire carries electrons that are accelerating different directions at any given moment, thus causing the 3 Hot wires to be out of phase from each other. At the same time, each Hot is out of phase with the Neutral wire. DC or direct current, produced by solar panels or batteries, causes electrons to move one direction only, and must be changed into matching phases of alternating current before being transmitted along power company wires. Resource: Household single-phase generator More about 3-phase generation How to set up solar array Why you need a ground wire |
 Larger image of gridSingle phase is a derivative of 3-phase from the power plant. Illustration shows 3 phase from power plant to household single-phase How it happens: 3 phase from power plant transmits 300,000-500,000 volts across groups of 3 Hot wires, accompanied by a Neutral wire. One Hot wire comes off each of the 3 coils inside the generator. The other ends of the 3 coils are connected together to form the Neutral wire. The result is Hot to Hot has potential voltage, and Hot to Neutral has potential voltage. The Neutral travels with the Hot wires and is bonded to the ground rod array to protect the grid against overvoltages, malfunctions and lightning. At the distribution level, there are still 3 Hot wires plus Neutral, but voltage has been reduced at substation transformers to 4500-7200 volts. Single phase is derived by taking one 7200 volt Hot wire and the Neutral off the 3-phase. The Hot and Neutral are then connected to residential transformer. Transformers at local substation reduce high voltage into 7200 volts so it can be distributed safely along wires that are suspended nearer to ground and can pass close to trees. Once power reaches each home and business, voltage is further reduced by transformers, ensuring that households and businesses receive safe and usable low volt, high amp power. It works nicely because household 120-240 voltage can be safely controlled by small switches, relays, cell phone chargers etc contained within steel and plastic enclosures, while the amperage (and heat) is controlled by circuit breakers (overcurrent protection) and then distributed to outlets, switches, dryer etc using correctly sized wire to match amp rating of breaker. Resources: See inside main breaker box Basic residential electric Why you need ground wire Wire and breaker size |
 Larger image   Voltage per turn x number of turns |
Residential
transformer for single phase service -Transformers work on the principle of magnetic induction where applying electricity to one coil of wire creates a magnetic flux that energizes the other coil of wire with electricity. -'Transformers have no moving parts, ensuring a long trouble-free life under normal conditions.' Inside a transformer are coils of wire called the primary and secondary windings. Each coil is wrapped around a laminated iron core or more efficient amorphous metal core. The metal core is shared by both coils, but the coils of wire are 'insulated' from each other. They are electrically separated. There is no wire in common between the primary and secondary coils, only the metal core is shared. How transformers work pdf -Having different numbers of turns of wire, or varying the turns ratio, on each coil will reduce or raise voltage. Different voltages can be achieved throughout the grid by varying the number of turns on the primary and secondary coils. -The 7200 volt Hot wire and Neutral are connected to primary coil via 2 taps H1 and H2 located on top of transformer. -Applying 7200 volt to the primary coil will produce 240 volt on the secondary side because the transformer selected for the job has the correct turns ratio for residential voltage. Connecting the 7200 volt Hot and Neutral across the transformer's primary coil 'completes the circuit' causing electrons to oscillate back and forth 60 times per second. This flow of electrons on the primary coil causes electrons on the secondary coil to oscillate in the same frequency. -The secondary side has 3 taps X1 X2 X3 located on side of transformer: 2 outputs X1 X2 for Hot wires and 1 output X3 in center for Neutral wire -Residential homes receive 3 wires consisting of 2 out of phase Hots and 1 Neutral. The Neutral wires on both primary and secondary side of transformer are bonded to the ground wire at the pole. All Neutrals throughout the grid are connected together and bonded to ground wires that connect to ground rods to create massive array of grounding that provides safety and stability to the grid. -To get 240 volt, you pull a Hot wire from each end of the secondary coil. These two Hot wires are out of phase from each other because electrons are oscillating back and forth on the secondary coil, and since each Hot wire is connected to a different end of the coil, each Hot wire carries electrons that are accelerating different direction from each other at any given moment of time. -By pulling a Neutral off the center of the coil, you get 1/2 voltage or 120 volt potential. As a result, 120 volt is achieved using 1 Hot and a Neutral. While 240 volt is achieved using a Hot wire from both ends of the secondary coil. -As a footnote, drawing 2 Hots from same side of coil yields no voltage when connected to an appliance since both Hots are in phase with each other... each Hot must come from the opposite end of secondary coil. Resource Why you need ground wire |
| More detail: Transformer construction. ''The core provides a low resistance path for magnetic flux. The iron core is typically made from very thin individual laminations, each coated with insulation. By insulating between individual laminations, losses from eddy currents that are magnetically induced on the iron core are reduced.'' Other losses include hysteresis loss, or heat loss, from iron atoms in the core resisting polarity change when the atoms realign with changing polarity caused by oscillating current, plus loss from resistance of the winding (wire) itself. ''Loss of efficiency is the ratio of power delivered on the primary side, to power delivered on secondary side. Transformer loss can range from .5 to 8%'', meaning 92-99% efficiency dependent on amount of amperage flowing through the circuit, and ambient weather conditions etc. Amp rating of overhead conductors 'Each phase of a transformer is composed of two separate coil windings wound on a common metal core. On some transformers, the low-voltage winding is placed nearest the core; the high-voltage winding is then placed around both the low voltage winding and core. Other transformers have separate coils that sit next to each other. Strength of a magnetic field depends on the amount of current (amps or number of electrons) and number of turns in the winding. When current is reduced, the magnetic field shrinks.' Primary vs secondary. ''The primary is always connected to the source of power, and the secondary is always connected to the load.'' So if home has solar power that feeds back into the grid, then the lower voltage side can become the primary when power is flowing from the home to the distribution wires.'' Another example, during a power outage, if the home or business generator is running, and connected to breaker panel and main breaker is not turned OFF, then electricity will travel through the transformer and energize distribution wires at full voltage. This creates electrocution hazard for linemen working to restore power, or clearing storm debris among downed power lines. Turns ratio. ''Electric field surrounding power lines is primarily a function of the voltage.'' ''The amount of voltage induced in each turn of the secondary winding will be the same as the voltage across each turn of the primary winding. The total amount of voltage induced will be equal to the sum of the voltages induced in each turn." This explains why the primary and secondary coils have different number of turns, and where the calculation comes from. Single-phase and 3-phase Current or amperage draw from power lines. The current is inversely proportional to both voltage and number of turns on the transformer. E volts N turns I amps (amps is current or flow of electrons).  If
primary volts E1 are 7200
volts, and secondary volts E2 for
household single-phase service is 240 volts. Suppose the main breaker
is 250 amps then I2 is
250 amps. With residential single-phase transformer, the turns ratio is 30:1. This means I1 can be calculated: 250 amp divided by 30 = 8 amps. This means the 7200 volt primary line must be able to deliver 8 amps to the primary coil ... ... during maximum usage. Voltage remains unchanged (unless there is a surge event): 7200 on the primary and 240 volts on the secondary, no matter how many amps are pulled by the household. Voltage drop does not occur in normal conditions because all circuits are wired in parallel, not in series. Since electricity is dynamic, and delivered on demand, 8 amps would only be consumed off the primary when the home was using maximum amps on all circuits. The 250 amp main breaker in household panel would be near to tripping off. The effect is multiplied when the distribution line supplies power to 100's or 1000s of homes and businesses. Compare the same amp draw for 3-phase. Primary volts E1 are the same 7200 volts. Let's suppose the main breaker is also the same 250 amps so E2 is 250. But let's change the secondary voltage E2 to 480 volts commonly found in a commercial 3-phase service. The turns ratio would be 15:1. This means primary amperage I1 can be calculated: 250 amp divided by 15 = 16 amps. This means the 7200 volt primary line must be able to deliver 16 amps to the primary coil. Except each leg of the 3-phase circuit pulls 16 amps, from 3 separate wires at staggered times as the generator rotates. Unlike single-phase that pulls 8 amps from 1 of the 3 Hot wires. Overall, the effect is that 3-phase delivers more power, more kVA or Kilo Volt Amps or Kilowatts. -37 strand bare aluminum alloy wire is among the commonly used distribution lines. The 7/8" diameter wire can carry 500-1000 amps depending on ambient weather conditions. Cooler temperatures, clouds, and wind help lower resistance, so the voltage can push more electrons (amperage) through the conductor matrix with less power loss. Photo taken during installation of power lines. NEVER touch a power line without 100% certainty the line is not carrying electricity.  If everybody on the distribution line was consuming maximum amps during a record heat wave, then the amperage on the power line would begin to heat the circuit breaker at the substation. If the substation breaker tripped the line, another circuit might pick up the load, but sometimes at reduced power, resulting in brownout where the voltage drops. Or loadshedding where sections of the grid are shut down for a period of time. Grid improvements for reliability have minimized the problem for short-run, but as summer temperatures increase, the practice of reducing consumption is best choice. Rooftop solar panels can likewise assist. Resources: Source page 6 Overheat power line proximity devices 20034865 page 3 How to wire generator transfer switch What causes electrocution Override air conditioner to reduce run time How many amps on power line |
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 Larger image |
Residential
single-phase breaker box After leaving the transformer, residential wires go to the meter box that records billable Kwh of electrical usage, and then into the main breaker box. Once inside the main breaker box, the 2 Hots and 1 Neutral are connected to 3 separate busbars. The 2 Hot wires are connected to the main breaker which is snapped over the top of 2 busbars. The two Hot busbars are electrically separated and never come into contact with each other. The Neutral is connected directly to the Neutral busbar which is always bonded to the Ground busbar. The ground busbar is connected to a ground wire going out to the ground rod (not shown). 240 volt comes from a double breaker that draws 2 wires, one wire from each Hot busbar. 120 volt is drawn from a single breaker that is snapped over either Hot busbar. \ Resources: See inside main breaker box Why you need ground wire |
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3-phase commercial electricity Illustration show 3 phase arriving at business The same 3-phase 7200 volt distribution wires used for residential power are used to supply 3-phase for businesses. Each Hot wire connects to a different transformer. The transformers work on same principle as residential transformers, with a primary and secondary coil, except wiring configurations are different. With residential transformer, voltages are uniform 120-240. But with commercial 3-phase service, there is a choice of voltages ranging from 208-208-208-120V to 480-480-480-277V to 600-600-600-347V etc, with 600V being the Hot-to-Hot line voltage, and 347 being the Hot-to-Neutral phase voltage calculated using a ratio of √3 or 1.732. Other common electric services include 120-240-208 high leg delta, and the wiring configuration, or the way wires are connected to the transformer taps, and the transformer selected for service are different, but the concept of primary and secondary remains the same. Some services do not have Neutral wire, but most do. All services are grounded. Once a voltage is selected for the service, the power company installs the correct transformers and configures the wiring different ways to achieve voltages specified for the building. Most businesses also have 120 volt Hot-Neutral single-phase available for outlets, same as a residential home, but usually the lights for commercial stores, buildings, schools etc are connected to higher voltage, for example 240 volt, 277 volt or 480 volt, to run more efficiently. Resources: What is 3-phase How to wire 3-phase Transformer configurations 3-phase transformers .pdf What is 208 volt What is 277 volt What is high leg delta |
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3-phase
breaker box Single-phase residential breaker box has 4 busbars with one busbar for Neutral, one for ground, and 2 Hot busbars. 3-phase breaker box is different and has 5 busbars with 3 Hot busbars, a ground busbar, and a Neutral busbar. Using a 3-pole circuit breaker, and taking 1 wire from each Hot busbar gives 3-phase electricity to run motors and equipment. Each Hot is out of phase with each of the other Hot wires. Taking 1 Hot wire and a Neutral, or 2 Hot wires instead of three, yields single phase from the 3-phase breaker box. The difference between commercial single-phase and residential single-phase is that voltage choices vary with 3-phase service. For example, you can get 120, 208, 240, 277,480 volt single-phase from a 3-phase service, depending on which transformers and which wiring configuration was specified for the service. 3-phase motors are connected with 3 wires, with each wire connected to a different winding inside the motor. Resources: How to wire 3-phase |
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Switching 3phase loads 20-40 amp loads can be switched using the manually-operated 3-pole motor control switch seen in illustration at top of page. Single phase is used for automated switching of 3-phase: a single-phase timer, thermostat, PLC, or electronic circuit is used. The illustration on left shows T104 timer activating a 3-pole contactor that turns the 3-phase load on-off. How it works: Pull 2 Hot wires off the 3-wire circuit to get single-phase. In this example, the 3-phase service is 208-208-208-120 WYE or 240-208-208-120 High Leg Delta. The available voltages are determined by type of transformer and transformer wiring installed by the power company. The coil on the contactor must be rated same voltage on wire, and meet or exceed amp rating of circuit. Resources: Contactors 3-pole contactors T104 timer How to wire 3-phase timer How to wire motor control contactor |
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More detail: Single-phase Sine wave shows 4 different aspects of 120-240 volt single-phase electricity. 1) Rise and fall of voltage over time on Hot Line 1 and Hot Line 2 found on typical 120-240 volt household electricity. 2) Average Voltage: Each time the electrons stop, voltage drops to zero, as represented by the center line showing 0 volts. As the electrons accelerate one direction on the wire, voltage rises as shown in TOP half of sine wave. As the electrons slow, voltage drops. Electrons stop momentarily and voltage reaches 0 volt again. As the generator keeps spinning, the electrons begin accelerating the other direction and voltage rises as shown in BOTTOM half of sine wave. The voltage rises to more than 120, but using calculus, it can be shown that the average voltage is 120 on each Hot wire. Average voltage is not accidental, and comes from mathematically engineered electric production that delivers standardized voltages across the grid. "Switching a relay or solid state switch at the zero-crossing point reduces spark across the contacts, extending relay life, and also reduces EMI (electromagnetic interference)." Resource: Extend life of relay by switching at zero cross .pdf 3) Time: The illustration shows the length of one cycle which is equal to one full rotation of the generator. This is called cycles, frequency or hertz. The generator in the US and Americas rotates 60 times per second. 4) Phase: Illustration shows how Line 1 and Line 2 are out of phase with each other, with electrons on each line accelerating different direction at any given moment of time. |
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More detail: 3-phase Sine wave shows 4 aspects of 3-phase electricity as it emerges from generator. 1) Rise and fall of voltage over time on Line 1, Line 2 and Line 3 found on 3-phase electricity. 2) Average Voltage: Power plant generator can produce 30,000 volts. Voltage reaches 0 on each individual line, but at no time does voltage reach 0V on all 3 lines at same time. This translates to higher average voltage per rotation of generator for 3-phase compared with single-phase. When 3-phase is connected to a motor, the average higher voltage means less amperage is needed, which means motor runs cooler. Amperage is the heat on the wire that trips a circuit breaker. Volts x amps = power (watts), so 3-phase can deliver more power with less heat loss, making 3-phase more efficient than single-phase. Lower amps also means that wires can be smaller, thus lowering cost of installation. "The horsepower rating of three-phase motors is about 150% greater than for single-phase motors with a similar frame size. The power delivered by a single-phase system pulsates, and the power falls to zero three times during each cycle. The power delivered by a three-phase circuit pulsates also, but it never falls to zero. In a three-phase system, the power delivered to the load is the same at any instant. This produces superior operating characteristics for three-phase motors." 3-phase circuits and basic math .pdf 3) Time: The illustration shows the length of one cycle which is equal to one full rotation of the generator. 4) Phase: Illustration shows how Line 1, 2 and 3 are out of phase with each other, with electrons on each line accelerating different direction at any given moment of time. |
| More detail: Three phase power can be transmitted longer distance using smaller conductor (wire) than single-phase, making it possible to transmit long distance at lower cost. Smaller conductors mean less weight so towers and poles can be located farther apart, further reducing cost. Electricity is volts and amps. Voltage is the force that pushes amperage along the wire. Amperage is the current of electrons flowing on the wire. Voltage is a potential between conductors, and generally remains steady, while amperage rises and falls with demand, with more electrons flowing on each wire when demand is high. The problem with high demand, when more loads are drawing power and more amperage is flowing, the hotter the wire gets, and the more energy is wasted. Heat occurs as voltage pushes amperage (current of electrons) against the matrix, or atomic structure, of the conductor. The conductor always offers resistance to the flow of electrons, and because resistance is like friction, a large current of electrons causes the wire to get hot. Each conductor is rated by ampacity or number of amps it can carry, with larger wires able to carry more .... with other factors playing a role too: For example, windy, cloudy and cool conditions allow more amperage with less heat loss, while hot sunny conditions reduce the amp rating and increase heat. If voltage is pushing too many amps (electrons) for the conductor rating, or the conductor is too small for load, then resistance causes the wire to get hot, resulting in power loss, inefficiencies and higher cost. If heat on wire exceeds the amp rating, then the breaker at substation will trip and protect the wire. Resource: Ampacities of power lines To solve the problem of heat loss, long distance transmission wires are high voltage and low amperage. Using high voltage and low amperage means more force is pushing fewer electrons against the conductor matrix, which means less resistance from the conductor and less heat.  High
voltage conductors are suspended high above the ground and spaced far
apart, utilizing air as an insulator. This is to prevent electricity
from jumping (arcing) to other wires, or to the transmission tower, or
to the earth. The higher the voltage, the more space is needed to
keep the voltage under control.High voltage also requires large and expensive switchgear, and is extremely dangerous, making it impractical and hazardous for ordinary residential and commercial use. (However, some industrial applications require high voltage and consume immense amounts of power, frequently needing their own substation and/or co-generation plant.) To solve the problem of high voltage, transformers are used throughout the grid to step up or step down voltage. Amps and volts are inversely proportional. When volts are lowered, amps are raised. Using transformers, the power company can change the volt-amp ratio to accomplish different objectives. | |
30 amp
breaker use 10 gauge / Buy 10-2 gauge/ 30 amp 10-3/ 30 amp Southwire electric tools |
Yellow 12 gauge 20 amp Yellow/ #12 gauge wire for 20 amp with ground Buy 12-2 gauge/ 20 amp 12-3/ 20 amp Rolls of stranded wire NMB is house wiring UF is underground |
White 14
gauge 15 amp White/ #14 gauge wire for 15 amp with ground Buy 14-2 gauge/ 15 amp 14-3/ 15 amp NMB is house wiring UF is underground |
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50-60 amp breaker use 6
gauge> Buy 6-2 wire Southwire electric tools NMB is house wiring UF is underground |
40-50
amp breaker use 8 gauge Buy 8-2 wire< Southwire electric tools NMB is house wiring UF is underground< |
 Copper ground wire Use same size as other wire in circuit Buy Spools of ground wire Ground rods at Amazon |
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