Electrical Engineering

An impedance diagram (sometimes called an impedance triangle) results when a series circuit's voltage phasor diagram is divided throughout by its reference phase (current) -this results in resistance (=VR/I), inductive reactance (=VL/I), capacitive reactance (=VC/I) and impedance (=V/I) andillustrates the Pythagorean relationship between the circuit's impedance, reactance, and resistance.

slip speed control refers to induction machines

s=(synchronous speed-motor speed)/synchronous speed

by varying slip the machine can be either be operate in generated mode or motor mode

A triac is a semiconductor-based solid state electronic switch. The main applications are those which require the electronic switching of AC circuits. The switching can go from 100% on to 100% off (or vice versa) or can allow only portions of each AC cycle to pass through, which varies the amount of power supplied to the load. That is how triac-based AC lamp dimmers work.

They are usually made of a plastic called urea-formaldehyde.

its a symbol

A == B

(- 12V +)

(- 12V +)

(- 12V +)

A single 12V battery in series with 4x 12V batteries connected in parallel...

Total voltage from A to B is 24 volts!

Note that the single battery in series will limit the total current capacity to that of a single battery.

The 7408 is a 2 input AND gate. This takes two logic signals and outputs a true if and only if both inputs are true. There are four gates on this part. There are numerous voltage levels based on the technology used (the silicon, etc.) to produce the part.

There is a good Wikipedia article here http://en.wikipedia.org/wiki/List_of_7400_series_integrated_circuits which shows the whole list of these gates. Understand that this is not necessarily the way the parts are numbered from the manufacturer. TI, for example encodes not only the part type (AND gate, etc.) but the technology and the packaging into the part number. While the packaging will not determine what logic rules it follows, it is important for the physical device to match its place on a board. An example of such a part from TI is an SN74LVC08. This is a Low Voltage CMOS part which is the 7408 part you refer to. The technology is omitted from the generic statement because the important thing is usually the function. The "SN" denotes the manufacturer, and the "LVC" between the "74" and "08" denotes the technology used. Note that the "74XX" is generally termed 7400 series logic, even if, for example the number is 74126 for a quad bus buffer.

The withstand voltage is the amount of electrical potential, measured in volts, which can safely be applied to an object in various environments, typically dry or damp or wet conditions, at normal atmospheric pressure and temperature.

The object must still remain functional after the voltage test has been completed.

This question refers to a test done in dry conditions.

The question also mentions power and frequency, which are attributes which refer to the type of electrical service being used to perform the test. The electrical service may be either alternating current, running at a certain frequency, or direct current.

Millionth is the name for the power of 10 to the negative 6 power. The prefix for this is micro.

Transmission line can be on H frame up to 66 kv, it can be on structral hollow MS/ wooden high Mast similar one used for illuniating open area , or letice strcutral tower , this depends on level of volatge and type of conductor, land profile and tower spoting.

Adv. Digital

· easy to store and use, that is why computers use it.

· Digital data is designed and artificially created, so it is efficient.

· Less expensive

. DSP is easier to reconfigure as it is made up of h/w as well as s/w.

Disadv. Digital

· Digital communications require greater bandwidth than analogue to transmit the same information.

. Due to Quantisation , an error is alwz there.

current that does't use in power measurement is called reactive current.

Gas insulated substations do have some advantages. They are preferred in cities and large towns, and are considered to be safe, reliable, and maintenance free.

The CT standard output is 5 amps at the rated input amps. The CT will have a marking like 400:5, 100:5, or similar, where the bigger number is the input current that will cause 5 amps to flow in the CT secondary. Divide the span by 5 to get the multiplier. For instance: CT - 400:5 400 / 5 = 80 So, if you measure, say, 3 amps from the CT, the primary current is: 3 * 80 = 240 A

The normal method for controlling output of an alternator is to vary the field current. In a PM alternator, there would be no field windings to control. The only way I could think of would be to vary the speed of rotation. This might work if the output was rectified (DC), but would be a problem if the output is AC, since the frequency would also change. I have not seen a PM alternator per se. Unusual.

It's outside the scope of this answer to go into the theory, but a 3 phase motor by convention normally rotates anticlockwise when viewed from the 'driven' end.

To check phase sequence, the usual method is to use a phase sequence indicator. Originally these were like a miniature three phase motor encased in a hand-held device. If the flying leads were connected RYB, BRY, or YBR, the disc in the psi would rotate anticlockwise. If the flying leads were connected RBY, BYR, or YRB the disc would rotate clockwise. Nowadays, the mechanical aspect of the phase sequence indicator has been repalced with solid state devices that indicate on one of two leds if the sequence is c/w or ac/w.

To check phase sequence you look for which phase out of the three phases peaks first. You could probably put each phase on an oscilloscope and see which one peaks first. Phase sequence is usually taken as positive anticlockwise from the reference voltage ( the phase that peaks the first).

Wood is relatively strong, weathers fairly well, is (or was, at least) readily available, and is inexpensive. Utility power generation is, after all, a for-profit business.

Ohm's law: voltage is current times resistance. Restating this; current is voltage divided by resistance, so increasing resistance would decrease current.

Go to your local Apple store and ask about the topic . I will also tell you that alot of positions are opening up because apple has just come out with a apple think pad when i did i got an application for the job and filled it out and received the think pad in the mail a week later

The windings melt. Also may start a fire if surround conditions permit.

The Canadians.

colosium

An op amp is made from transistors, resistors and capacitors. It is enclosed in a "chip".

A basic instrumentation amp is made of 2 op-amps.

you can't have a single op-amp perform as good as a instrumentation amp, although it can perfrom the same task.

An i-amp has much better CMMR (common-mode rejection) and a higher input impedance.