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WYE and Delta are terms used to describe commercial 3-phase wiring configuration for transformers used in the electric grid
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Difference
between Delta and Wye
WYE and Delta are terms used to describe commercial 3-phase wiring configuration for transformers used in the electric grid |
 Fig 1-1 WYE 3 coils wired in parallel 120-208 volt
4-wire 3-phase with ground
3 transformer coils (windings) wired in WYE configuration : The 3 coils are wired in parallel with each other. Amperage on each line equals amperage on each coil. Phase Voltage between Hot and Neutral is same for each line. When windings are connected wye, the voltage between any two lines (line to line) will be 1.732 times the phase voltage (line to neutral), and the line current will be the same as the phase current. The common point of the three windings is called the neutral because equal voltages exist between this point and any of the three phases. Resource What is 208 volt What is 277 volt |
 Fig 1-2 Delta 3 coils wired in series ... end to end 120-208-240 volt
4-wire 3-phase with ground
3 transformer coils (windings) wired in Delta configuration : The 3 coils are wired in series with each other, like batteries end to end. Amperage on each line is 1.732 times the amperage on each coil. Higher amperage means more amps per volt, giving more power per volt. Each line carries the same voltage. When transformers are connected delta, the line current will be 1.732 times the phase current, and the voltage between any two will be the same as that of the phase voltage. Resources Transformer Basics pdf 3-phase power math .pdf What is high leg delta |
 In a wye connected
system, the line voltage is higher than the phase voltage by a factor
of the square root of 3 (1.732).
Line current and phase current are the same in a wye connection. |
 The line current of a delta connection is higher than the phase current by a factor of the square root of 3 (1.732) Source: 3-phase power math .pdf Delta transformer calculations .pdf |
| Transformers Transformers are used throughout the grid to accomplish different objectives. Transformers control the inverse relationship between voltage and amperage. Raise the voltage and the amperage goes down. Lower the voltage and the amperage goes up. For example, wires leaving the power plant might carry 500,000 volts. The high voltage means low amps and low heat on the wire which allows economic long-distance transmission of electricity. While high voltage is good for transmission, the switchgear and wiring needed for 500,000 volts is too large, expensive and dangerous for ordinary use inside a home or building. Using transformers, the power company can change the volt-amp ratio. The result is homes and buildings receive low volt, high amp power. It works nicely because 120-240-208-277-480 volt power can be safely controlled by small switches, relays, cell phone chargers etc contained within steel and plastic enclosures, while the amperage (heat) is controlled by circuit breakers and then distributed to outlets, switches, motors, lights etc using correctly sized wire to match amp rating of breaker. WYE and Delta wiring configurations are one method of using a transformer to reach a volt-amp objective. |
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| Before going farther, it's
important to describe how a transformer works. Transformers work on a basic principle of magnetic induction where applying electricity to one coil of wire creates a magnetic flux that will energize the other coil of wire with electricity. How transformers work pdf Inside a transformer are two coils of wire called the primary and secondary coils. Each coil is wrapped around a laminated iron core or more efficient amorphous metal core. The metal core is shared by both coils, but both coils of wire are 'insulated' from each other. They are electrically separated. There is no wire in common between the coils, only the metal core is shared.  Having different numbers of turns of wire, or varying the turns ratio, on each coil will raise or lower voltage. Different voltages can be achieved throughout the grid by varying the number of turns on the primary and secondary coils. The power company connects 4500-7200 volts from the distribution lines to the primary coil. This produces voltage on the secondary coil. Different transformers are selected depending on the voltage specified for end user. The end user's wires are connected to the secondary coil and power is routed into the main breaker panel. |
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 Illustration shows WYE-WYE electric service Primary side of transformers is wired in WYE Secondary or customer side of transformers is wired in WYE This is typical of WYE, 4-wire, 3-phase service Common voltages include: 120-208 and 277-480 120 and 277 are the Phase voltages measured between 1 Hot and Neutral 208 and 480 are the Line voltages measured between 2 Hot wires |
 Illustration shows WYE-Delta electric service. Primary side of transformers is wired in WYE Secondary or customer side of transformers is wired in Delta This is typical of High-Leg Delta, 4-wire, 3-phase service Common voltages include: 120-208-240, and sometimes 240-418-480 120-208 are the Phase voltages measured between 1 Hot and Neutral 240 is the Line voltage measured between 2 Hot wires |
| Figures 1-1 and 1-2 above are
representation of wiring for WYE and Delta on the secondary side of three transformers. Typical 3-phase service has 3 secondary coils. There are variations (not shown on this page) called Open WYE and Open Delta etc that have 2 coils. The actual appearance of wiring is different than the representations above. For example, the transformer coils do not actually touch each other. Instead they are connected by a wire. Figure 1-1 WYE represents each transformer coil as a zig-zag line. WYE (star) transformer coils (windings) are wired together to form the Neutral wire. There is 1 common point shared by each of the 3 coils of wire as shown in Figure 1-1. The common point gives rise to the Neutral wire. The other end of each coil gives rise to the 3 Hot wires. Measuring voltage from the center point to end of any coil is called the phase voltage. This can be seen in Fig 1-1 as 120 volts. Other WYE services can have different voltages depending on the turns ratio selected for the service. The voltage measured between any 2 Hot wires is known as the line-to-line voltage or simply as the line voltage. This can be seen in Fig 1-1 as 208 volts. In a wye connected system, the Hot wire to Hot wire line voltage is higher than the phase voltage by a factor of the square root of 3 (1.732). So 120 volts x 1.732 = 208 volts. In a wye-connected system, phase amps (current) and line amp are the same. Fig 1-2 Delta represents each transformer using four uuuu's. >Delta transformer coils are wired end to end. The Neutral wire if present is achieved by tapping into center of 1 coil. 'Line voltage and phase voltage are the same with Delta. If you measure Hot wire to Hot wire, you get same voltage as measuring both ends of one coil. However the amps vary between line voltage and phase voltage. Unlike Wye where phase and line voltage stay the same, with Delta, the line amperage is higher than the phase amperage. If phase amperage measure across one coil is 10 amps. the line amperage measured across two Hot wire is 10 amps x square root 3 or 1.732 = 17.32 amps. As the generator spins, and voltage on each wire rises and falls, each Delta coil is energized at different times. At any given time, two of the three coils are energized. This adds extra current when measuring between the Hot wires.' Delta has lower amps/ meaning less heat. For example many transformer banks are wired Delta on the Power company or Primary coils, and Wye on the customer or secondary coils. The reason for this: the distribution voltage connected to primary side can be 4500-7900 volts, and using delta configuration means lower amps which means the manufacturer can use smaller wires on the primary side coils and save money, yet still deliver full power to the customer. Materials used for the power grid are a balance of cost, safety, and function. Star-Delta (WYE-delta) is also a configuration used for motor starter timers, such as a star-delta timer. With motors, they consume more amperage to start. To reduce the expense and heat, the motor is started with the star or wye configuration, and after the motor starts, the circuit is switched to delta for higher efficiency. Why use 3-phase "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 with basic math .pdf How to identify transformer wiring What is 3-phase How to wire 3-phase 3-phase timer |
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| Why do they use a combination of Wye
and Delta configurations? "The four most common three-phase transformer configurations are wye-wye, delta-delta, wye-delta, and delta-wye configurations. Each configuration presents different characteristics. WYE-WYE or Delta-Delta configuration, the voltage, current, and phase relationships between the primary and the secondary are identical to the relationships found in a conventional single-phase power transformer. This means that the values of the line voltages and currents at the secondary are equal to those of the line voltages and currents at the primary." WYE primary Delta secondary: Line voltage relationship √3: 1 Line current (amp) relationship 1: √3 Phase shift 30° lag Delta primary WYE secondary: Line voltage relationship 1: √3 Line current (amp) relationship √3: 1 Phase shift 30° lead |
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| Use only 600 volt wire. Lamp cord, extension cords are not rated 600 volt. Use copper wire only. Aluminum wire is fire risk and should be avoided or installed by professional. 30 amp breaker use 10 gauge / 120-240 volt 30 amp outlet can be installed on 30 amp breaker only/ use 10 gauge wire ... cannot be connected to 15-20-40 amp breaker.  Orange/ #10 gauge wire, with ground ... 30 amp capacity. Safe maximum: 30 x 80% = 24 amps. Buy: 10-2 gauge/ 30 amp 10-3/ 30 amp Southwire electric tools |
Yellow
12 gauge 20 amp 120 volt 20 amp outlet can be installed on 20 amp breaker, but not 15 amp breaker/ use 12 ga wire. ... cannot be connected to 30-40 amp breaker. 1  Yellow/ #12 gauge wire, with ground ... 20 amp capacity. Safe maximum 16 amps. Buy: 12-2 gauge/ 20 amp 12-3/ 20 amp NMB is house wiring UF is underground Rolls of stranded wire HOOK UP Wires |
White
14 gauge 15 amp 120 volt 15 amp outlet, AFCI, GFCI, timer, switch etc can be installed on 15 or 20 amp breaker. Never connect 15 gauge wire to 20-30-40 amp breaker.  White/ #14 gauge wire, with ground ... 15 amp capacity. Safe maximum 12 amps. Buy: 14-2 gauge/ 15 amp 14-3/ 15 amp NMB is house wiring UF is underground |
| 50-60
amp breaker use 6 gauge / 240 volt 50 outlet can be installed on 50 amp breaker only  Buy: 6-2 wire Southwire electric tools NMB is house wiring UF is underground |
40-50
amp breaker use 8 gauge / 240 volt 40 amp outlet can be installed on 40 or 50 amp breaker only  Buy: 8-2 wire Southwire electric tools NMB is house wiring UF is underground |
  Copper ground wire. Every device, load, metal enclosure etc must be grounded. Ground wire must be continuous throughout installation, never switched on-off, never used as a Neutral wire. Generally ... use same size as other wire in circuit Buy: 12 gauge copper ground wire Ground wire Green ground wire Ground pigtails Ground rods/ ground clamps at Amazon |
 Non metallic flexible cables must carry ground wire, but do not have hazard of short circuit causing injury from shock. Armored steel cable can be used as a grounded connection, and will protect wires from damage. Metal can be energized from an insulation failure. All conduit ...metal, plastic ... flexible and rigid ... must be attached to structure, and attached to enclosures, boxes. Movement, damage and deterioration are major cause of electrical failure. Buy: Non-metallic flexible conduit Power whip Armored cable Southwire armored cable cutter Pull boxes |
 Electrical tools must be insulated. Always best to disconnect power, but insulation failure, lack of proper grounding, grounded neutral, lack of GFCI, out-of-code wiring, generator operating without transfer switch, and other problems still pose a risk to anyone working on electric power ... even when breaker is off. Buy: Electrician tools kits KLEIN TOOLS Tools kits IRWIN tools KNIPEX Telephone cable knife Low Voltage Mounting Bracket for Telephone |
 600 volt 12 ga Stranded wire ot THHN wire is good for conduit with multiple wires ... but stranded cannot be installed under screw terminals on outlets, switches, timers etc without risk ... of heat causing splayed strands ....that come loose ... and begin to arc. Connect stranded to short piece of solid copper wire, and attach solid to screw terminal. Do not solder residential or commercial wiring. Project wire, extension cords, thermostat, bell and automotive wire are not rated for residential or commercial wiring. Only wire maked 600 volt can be used for permanent household wiring. Buy: Southwire 600 volt stranded wire Rolls of stranded wire HOOK UP Wires |
 Protect wiring from damage Use nipper instead of pliers or screwdriver for removing staples (and nails). Do not damage cable or wires inside cable. -Code says: Cable SHALL BE secured without damage to the outer covering. NEC sec. 336-15 Buy End cutting nippers at Amazon |
  Electrically insulated tools When removing insulation from wire, do NOT score or put cuts on surface of copper wire. Doing so increases resistance and heat on wire and creates possible weak point. Buy tools: KLEIN TOOLS Wire strippers at Amazon Electric Wire Stripping Machine Linesman pliers Utility knife at Amazon |
 Multimeters Voltage is tested across two separate wires. Ohms or resistance is tested across both ends of same wire. Amperage is tested along one or two points on same wire. Buy: Analog multimeter Multimeters at Amazon Klein multimeter Electric testers at Amazon Clampmeter for testing amp flow on line |
 GFCI circuit breaker A GFCI circuit breaker will protect all boxes on circuit. Circuit must be grounded. Ground wire must be continuous and connected to each piece of equipment. White wire on circuit breaker must be connected to Neutral busbar inside the breaker panel. Buy GFCI circuit breakers |
Push down 1" wide Push down breaker Plug-in breaker Buy single-pole: Choose from 15 to 60 amp Eaton CL series Siemens 15-60 amp Single-pole tandem breaker Tandem breakers |
Push down 2" wide Push down breaker Plug-in breakers Buy double-pole: Choose from 15 to 125 amp Choose from 15 amp to 200 amp Eaton CL series circuit breaker Siemens circuit breaker Double pole GFCI |
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