Electrical Engineering

208 v. equipment is a little smaller and cheaper, and 208v. is slightly safer to use. However, 480v. runs on half the amperage 208v. equipment does, which means equipment or devices cost almost 50% less to operate.

With respect to energy consumption, the answer above is incorrect. It is true that equipment that operates at 480v does operate at roughly half the amperage vs. 208v, however, it operates at over twice the voltage. Your local power company charges you per kilowatt hour (voltage x amperage), not on amperage alone.

Example, a 208v motor that draws 10 amps would consume (208v x 10a) 2.080 kilowatts per hour.

The same motor on 480v would draw roughly half, 4.3 amps (480v x 4.3a) and would also consume 2.080 kilowatts per hour.

So in terms of power consumption, they are virtually the same. The main reasons one would opt for higher is the fact that you can install smaller wire and you can run longer distances.

It's a ratio that is directly proportional (at least with electric motors/inductive loads). If you were comparing a 240v motor to a 480v motor the ratio would be exact, if a 480v motor draws 5 amps, the same motor on 240v would draw 10 amps.

Ohm relay.......

The wattmeter will read downscale (backwards).

The mean load voltage, in other words the average voltage, is zero in an ac system.

Due to armature reaction

To bend a copper flat bar, first, you should heat the area you want to bend using a torch to make the metal more malleable. Once heated, you can use a bending tool or vise to gently shape the bar to your desired angle. Always wear appropriate safety gear and work in a well-ventilated area when using torches. After bending, allow the copper to cool gradually to maintain its strength.

The output from a DC generator is not pure DC due to the presence of ripple voltage, which results from the mechanical commutation process. As the generator's rotor rotates, the commutator segments switch connections, leading to fluctuations in voltage. While the output is predominantly direct current, these variations can cause it to deviate from a perfectly smooth DC signal. Additional filtering may be required for applications needing a more stable output.

For decrease the rectifier number

The operation of inverting direct current(DC) to alternating current(AC) is commonly achieved by utilizing the DC source(battery, solar panel, etc.) to generate a sinusoidal waveform at 60Hz which is the same type of shape as a household AC outlet. The waveform is created at very low voltage levels by small electronic components arranged in a circuit called an oscillator. With that small waveform, another circuit will boost it using different types of amplification methods such as transformers, Field Effect Transformers or circuits of the kind. The final AC voltage is in turned controlled by a regulating circuit which increases the power output from the amplifier to match the load requirement of your devices.

Bare in mind that in order for one to achieve 10Amps of AC at 120 Volts, a 12 Volts battery would need to supply approximately 100 Amps to the amplifier circuit.

Here is an example

P = Power = Voltage(V) x Current (I)

If you have 12 V, you need roughly 42 Amps to generate 500Watts

If you have 120V, you need roughly 4.2 Amps to generate 500Watts

therefor, you need 42Amps at 12V to provide a 500Watts load at 120V

A part of electricity.

Power Factor ranges from zero to one. Watts which is a measure of the work being done is Volts x Amps x PF. As you can see it is most efficient to have a PF = 1. The PF is the measure by which the current waveform is out of phase with voltage waveform. They are in phase for a pure resistive load and deteriorates with inductive loads like motors.

Electric Generator. :)

In 120/208V 3 phase system you have 5 wires: three hots, one neutral, and one ground. You have 208V between any two hots and 120V between any hot and neutral. The neutral is the same as in a single phase system. Clarification: Only 4 wires maximum come from the pole - 3 phases and a neutral, and then only if the transformers are on the pole. The ground is always locally derived from a ground rod(s) and/or cold water pipe ground. Most of the time, only 3 wires come in from the pole - the 3 phases in a Delta configuration (Delta has no neutral). The neutral is then derived from a local transformer connected in a Delta-Wye setup. The neutral is the center connection in the Wye. So, from the utility feeder to the transformer - 3 wires. From the transformer (wherever it is located) to the building service entrance panel - 4 wires. The ground is connected at the service entrance panel, and from there to the rest of the building you would have all 5 wires. Clear? In the US, 208/120 is a standardized mains voltage, but in some parts of the world, the phase-to-phase voltage is 220. In that case, the phase-to-neutral potential (in a 3-phase system) would be 127 Volts, not 120.

One ohm is the resistance through which a current of one ampere will induce an electrical potential difference of one volt.

Ohm's Law: Resistance is Voltage divided by Current

Ni chrome is a low resistance wire used in heaters and toasters.

What is meaning of Transformer sensitivity?

choke is used before drives to reduce the source supply fluctuation problem , which will effect drives

you match the frequencies but with a 90 degree phase shift

A cable tester is used to test the electrical connections in a cable or other wired device. There are two ways to test for a connection: continuity test and resistance test. A cable tester can also test for a short by determining voltage.

The Dielectric Discharge (DD), sometimes called re-absorption current, test is performed during the discharge cycle after the test. There are three components of current (charging, polarization and leakage currents) present during a standard insulation test, which make it difficult to determine the dielectric discharge.

Rather than measuring the polarization current during an insulation test, the DD test looks at the de-polarization and capacitive discharge currents at the conclusion of the insulation test.

The device under test (DUT) must be charged for an adequate amount of

time to be stabilized therefore, the only remaining current component is

leakage current. The DUT is then discharged at the completion of the

insulation test and the current flow is measured during a standardized time

of one minute. This current is dependent on the overall capacitance and the ending test voltage.

Dielectric discharge is calculated as:

Dielectric Discharge = I (after 60

seconds) / Volts x Capacitance

The DD test can identify excess discharge currents that happen when a layer of multi-layer insulation is damaged or contaminated. This condition will be missed by both the spot test and the Polarization Index test. Discharge current will be higher, for a known voltage and capacitance, if an internal layer is damaged. The time constant of this individual layer will differ from the other layers, causing a higher current than for insulation that is good.

Homogenous insulation will have a DD value of 0 while good multi-layer insulation could have a value as high as 2.

Source: http://www.aemc.com/

It works on the principle of "MAGNETIC LOCKING". When two unlike poles are brought near each other, there exists a tremendous force of attraction between those two poles.

Two years and about 60 credits.

i don't know......sorry =)