Electrical Wiring

I'm not an electrician and someone else can surely give you a better answer than this, but here goes: * Electricity- is the reason why electronics has a function to used by man. -support our appliances.

* Electronics are the things that need electricity to run on. Electronics are things like stereos, graphic equalizers, car stereo amplifiers, the guts of a GPS device, etc., ... it can also refer to the stuff inside these devices like wires, circuit boards, capacitors, resistors, RAM, circuits, etc. Example:

Here's an anology: Imagine one of those old grain mills next to a creek that's powered by the running water. The water would be like the electricity and the gears, wheels, and presses inside would be the electronics.

Whichever way it is connected, no matter whether it is in a star configuration or in a delta configuration, a 3-phase motor's start-up current can be more than 4 times its normal running current.

If the star configuration is used when first switching-on power to a 3-phase motor, a much smaller "start-up surge" is forced onto the power lines than if it were switched-on directly in the delta configuration.

So "using star for start-up" achieves very worthwhile purchase cost savings because smaller circuit breakers and thinner 3-phase line wire sizes can be installed to supply power to the motor.

However, leaving it running in star has a major disadvantage: the motor can never deliver as much power and torque as when it is running in delta.

For that reason a 3-phase motor was usually started in star mode and then - after reaching a steady speed - switched over to run in delta mode to achieve its maximum power output.

The explanation for this is easier to understand if you draw a sketch of the wirings and their connections, but unfortunately we cannot use diagrams when giving an answer here! Anyway, if you draw the circuit diagram for the windings connected in a "star" or "Y" configuration, it should look like a three-pointed star, with a phase input power line attached to each point of the star.

Thus, when a 3-phase motor's three windings are connected in a star configuration, the current from each individual phase power input line goes directly into one winding and is then series-connected to both of the other two windings via the star's "center-point".

If you draw the circuit diagram for a delta configuration, it should look like a triangle with a phase power input line attached to each point of the triangle.

Thus, when a 3-phase motor's three windings are connected in a delta configuration, each winding is effectively connected directly to two phase supply lines. The third phase supply line is also connected to that winding, but indirectly via the other two windings. They are connected in series to one another, and that series pair is connected in parallel across the first winding, to form the "delta".

The much lower starting current is the main reason why a three-phase motor was usually started in star mode and then - after gaining a steady speed - was switched over to run in delta mode to achieve its maximum power output.

Update: Electronic motor-control systems, which offer soft-starts in DELTA configuration, are now replacing the use of manual or semi-automatic star-delta starters.

Technical explanation

When the windings of a 3-phase motor are connected in STAR:

• the voltage applied to each winding is reduced to only (1 /.'/'3) [1 divided by root three] of the voltage applied to the winding when it is connected directly across two incoming power service lines in DELTA.
• the current per winding is reduced to only (1 /.'/'3) [1 divided by root three] of the normal running current taken when it is connected in DELTA.
• so, because of the Power Law V [in volts] x I [in amps] = P [in watts],

  the total output power when the motor is connected in STAR is:

  PS = [VL x (1/.'/'3)] x [ID x (1/.'/'3 )] = PD x (1/3) [one third of the power in DELTA]

  where:

  VL is the line-to-line voltage of the incoming 3-phase power service

  ID is the line current drawn in DELTA

  PS is the total power the motor can produce when running in STAR

  PD is the total power it can produce when running in DELTA.

• a further disadvantage when the motor is connected in STAR is that its total output torque is only 1/3 of the total torque it can produce when running in DELTA.

For more information please see the answers to the Related Questions shown below.

This Answer is the same as the for the Question 'Why is power for a country's mains grid usually generated as 3-phase electricity not single phase?'

Single phase power has a sine wave voltage that crosses zero before reversing its polarity. In the region near the zero-crossing there is not much power. At zero there is none at all. So single phase loads often need some trickery to deliver output in this area. Often it is just the inertia of the motor or appliance.

Three phase power is always delivering power on one of its phases, and is thus preferred for machines, motors and appliances that use lots of power.

Three phase power generation is preferred if the application needs very high power, or nees relatively small power output but with with weight restrictions - as in automobiles, where the power is generated in a 3-phase alternator and then converted to DC using rectifiers!

Use of DC (Direct Current) is the next step up for smooth high-power devices but requires rectification, regulation and smoothing to be useful.

Another problem with DC is that, for efficient long distance transmission, it cannot be simply converted to much higher voltages than the voltage at which it was generated at the power station.

Similarly DC cannot - simply by using transformers - be converted down to safer, much lower AC mains voltages for use by consumers.

Conversion of DC to AC requires the use of expensive high-power electronic "power inverter" systems and the opposite - the conversion of high-power AC to DC - requires the use of very big power rectifiers.

AC (Alternating Current) is used for high power generation and distribution because it can easily be transformed, using transformers, to achieve very efficient power transmission over very long distances and can then be transformed down to low voltages for distribution to consumers.

Two phase, and higher multi-phases are also used, but very rarely, for a few very specialised applications.

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A three phase system provides constant torque, whereas single phase does not.

With three phase you will get more power per kilogram of metal to generate electrical energy.

For a given load, a three-phase supply uses less copper than a single-phase system. In other words, it's more economical!

the necesscity of two three phase transformers operating in parallel are as follows...

• if the one transformer fails to give supply,then another transformer can be used in parallel and hance,continuity of supply can be maintained.
• one transformer can be easily take out from the supply for repair & maintanance.
• if the load on the substation increases beyond the rated values of transformer, then another transformer can be used to share rhe load of the substation.

If you had to ask this question here you need to learn more about your local wiring code re all the items you must use for this new motor circuit.

So that the new installation is safe and legal - and complies with the terms of your home or business insurance policy - you must use the correct type and size of cable, the correct type of circuit breaker and the correct type of wall outlet.

Serious home fires can result from incorrectly-installed new circuits.

Another answer

NEC table 430.248 lists this motor as drawing 17 amps, !7 x 1.25 =21.5 amps. Number 10 copper wire.

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As always, if you are in doubt about what to do, the best advice anyone should give you is to call a licensed electrician to advise what work is needed.

Before you do any work yourself,

on electrical circuits, equipment or appliances,

always use a test meter to ensure the circuit is, in fact, de-energized.

IF YOU ARE NOT ALREADY SURE YOU CAN DO THIS JOB

SAFELY AND COMPETENTLY

REFER THIS WORK TO QUALIFIED PROFESSIONALS

An LED, or light emiting diode, can have many functions. Commonly used as a solid state light emitter, LEDs of nearly any color of light are available, including ultraviolet and infrared.

A less obvious use of a light emitting diode is to detect light. A LED makes a very efficent and narrow band light detector. It will produce electric current in response to light that is about the same wavelength (and therefore color) as when it is used as an emitter.

Another use of an LED is to make a fairly stable voltage reference; A red LED when forward biased will have a steady voltage drop of about 1.8 volts, an orange LED produces a voltage drop of about 2.0 volts, and about 3.5 volts for blue and white emitting LEDs.

LEDs can be used as modulated light emitters to transmit speech, music and digital information. A good example is a television remote control which digitally pulses a infrared LED to change channels, control volume, and so on.

LEDs are used in solid state switches when optically coupled to a photodiode or photo resistor. LED flashlights are very common, and some small light bulb replacements are available, with larger bulb replacements soon to come. Some links are provided below:

Use one leg of the 240v and the neutral wire. Most electric dryers run the motor this way. The heating element is 240v but the motor is 120v.

NO, THAT IS DANGEROUS ADVICE because a 240 volt service has a circuit breaker which is sized for the current draw of a large 240 volt appliance, so it would have a rated amperage that is too high to protect a 120 volt motor running on its own.

Only 240 volt appliances such as dryers, air conditioners, etc. are safe to use on 240 volt circuits.

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As always, if you are in doubt about what to do, the best advice anyone should give you is to call a licensed electrician to advise what work is needed.

Before you do any work yourself,

on electrical circuits, equipment or appliances,

always use a test meter to ensure the circuit is, in fact, de-energized.

IF YOU ARE NOT ALREADY SURE YOU CAN DO THIS JOB

SAFELY AND COMPETENTLY

REFER THIS WORK TO QUALIFIED PROFESSIONALS.