Electrical Wiring

A "three-phase system" is a polyphase system having three phases. The term "polyphase system" just means a system having multiple phases. If it is used by itself, "a polyphase system" doesn't mean "a three-phase system".

In a vacuum breaker the moving contact and fixed contact are sealed inside a vacuum chamber. Electrons cannot flow in a vacuum, therefore as soon as the moving contact seperates from the fixed contact the arc meets an infinite resistance and is immediately extinguished. Because of this, the gap between the fixed and moving contacts when the breaker is open need only be a tiny amount.

so the workplace is tidy

You have to know the power loading and phase angle (or power factor) between each pairh of the phases, otherwise you could be making serious errors.

The reactive power depends on the load and not the generator. Reactive power can be detected at the generator, and the load disconnected if there is too much being drawn.

A generators's voltage depends on the speed, and the power produced depends on the current in the field winding.

An alternator running on a bus bar, as in a grid system, runs synchronously with the grid it is connected to. In this case the power produced depends on the rate that steam is supplied to the turbine, and although the speed stays constant, any increase in power output is accompanied by an advance in the phase angle of the rotor.

A transistor works by using a small amount of electricity to control a much larger supply of electricity, much like turning a valve to control a supply of water.

Transistors consist of three main parts - a base, a collector, and an emitter.

The base is the part for the larger electrical supply. The collector is the larger electrical supply, and the emitter emits that supply. By sending different levels of currents from the base, the size of the current can be regulated to the collector In this way, a very small amount of current may be used to control a large amount of current, like an amplifier.

ANSWER: A VOM can identify the transistor as NPN PNP just by checking the diodes inside the transistor. Example NPN positive lead to base should show low resistance to the other terminals

Any two legs of the 480V will give you 240 V Single phase.

I apologize for the wrong information here. A friendly member reminded me of the correct answer.

I stand corrected. Any two legs would be at 480 single phase. One leg to neutral will give you 277volts not 240 (408/1.73). You would need to install a step down transformer on the 277v line to achieve 240v.

Disadvantages of DC:

* High power transformation of voltage is less convenient than AC. AC uses a transformer.

* DC does not have the natural break in transmission that AC has (zero twice per cycle) and does not switch off as easily

* DC does not provide time to synchronous clocks * DC dynamos or generators are less efficient at converting input power to output electricity than AC alternators. That is why altenators with rectifiers are now used in vehicles instead of DC dynamos.

A zigzag transformer is used in connection with 3 phase and is made up of 6 coils connected in a "Y" manner. Each leg of the "Y" is made up of a coil on a different phase leg of the transformer. The neutral formed by the zigzag connection is very stable. Therefore, this type of transformer, or in some cases an auto transformer, lends itself very well for establishing a neutral for an ungrounded 3 phase system. Many times this type of transformer or auto transformer, lends itself very well for establishing a neutral for an ungrounded 3 phase system. Many times this type of transformer or auto transformer will carry a fairly large rating, yet physically be relatively small. This particularly applies in connection with grounding applications. The reason for this small size in relation to the nameplate KVA rating is due to the fact that many types of grounding auto transformers are rated for 2 seconds. This is based on the time to operate an overcurrent protection device such as a breaker. Zigzag transformers used to be employed to enable size reductions in drive motor systems due to the stable wave form they present. Other means are now more common, such as 6 phase star.

Simply because it is cheaper. (You dont need the extra wire)

However you can only use a 3 wire system if the load is a balanced load. If the load is not balanced you need the fourth wire (neutral/return) to take the out of balance current.

Developing solution is a common BPR phase that includes detailed process definition, system requirements writing and system development, training development, implementation planning, operational transition plan, pilots and trials.

Yes, just use L1 and L2 ( just 2 of the 3 legs), or one of the legs to a neutral wire if equipped. Just make sure the voltage is the same as the 220 volts you wish to have with single phase service.

It increases. The time constant of a simple RC circuit is RC, resistance times capacitance. That is the length of time it will take for the capacitor voltage to reach about 63% of a delta step change. Ratio-metrically, if you double the resistance, you will double the charge or discharge time.

Two wattmeter method is used in a three phase sysstem to measure the true power without regard to the balance ie. It can be used to measure both balanced loads and unbalanced loads.
The three phase power could be measured using single phase wattmeters in each loads of the system. But using three wattmeters is quite unnecessary as we can measure it by using only two wattmeters.

The three phase power could be measued by using single phase wattmeters , haing a current coil in one line and a potential coil connected between the line and some arbitrary common junction point. If that arbitrary common point is chosen on one of the three lines, then the wattmeter connected to that line will indicate zero power because it's potential coil has no voltage across it. hence, that wattmeter may be eliminated, and the three phase power can be determined by means of only two single phase wattmeters.

You should not need a wiring diagram. If the generator has a star point (wye) connection then the phase voltage to ground (star point) is 277 volts. 480/1.73 = 277.

Both of these devices are safety devices used to open a faulted circuit and stop the current flow.

Wow your in some serious stuff. Are you worried about rotation. 4160 is not something to be messed with if your not a qualified electrician or lineman. If you mess up you can have a big fire ball on your hands.

Just use 2 of the wires instead of 3.

Current (measured by an ammeter)

and

Voltage (measured by a voltmeter)

R= V/I

Resistance equals voltage divided by current

================================

That's wonderful, but the measurement doesn't "affect" the resistance

of the wire.

The factors that do "affect" the resistance ... i.e. determine what the

resistance will be ... are

-- substance of which the wire is composed

-- dimensions of the wire: thickness and length.

Terminology gets misapplied but a 3-phase converter produces a 3 phase supply from a single phase supply. The only proviso is that generator, converter and motor are all suitably rated and compatible.

For power factor improvement so that the KVA demand is reduced.

7.5kVA is a value derived from the voltage multiplied by the current.

Without knowing one, you cannot know the other.

For example, think of the number 10kVA

This could be made by :10kV * 1A or 5kV * 2A or 1kV * 10A or 2kV * 5A.

You couldn't possibly know which is the initial pair.

The current is the same in the three live wires. The voltage can be described as the line voltage (phase to neutral) or the phase voltage (phase to phase) which is larger by a factor of sqrt(3).

So a line voltage of 230 v corresponds to a phase voltage of 400 v.