Electrical Engineering

Yes, most large motors are three phase. Usually single phase motors only go up to 10 HP. Larger than this and the wire size and contactors used to control the motors becomes extreme. For example a single phase 10 HP motor on 115 volts draws 100 amps. The same single phase motor on 230 volts draws 50 amps.

The same 10 HP motor on three phase system draws the following amperage; 230 volts is a 28 amp draw, 460 volts is a 14 amp draw and 575 volts is a 11 amp draw.

As you can see the higher the voltage becomes, the smaller the wire feeder size is needed and much smaller size contactor can be used to control the motor.

VA, or volt-amperes, is a measure of the output of the transformer. VA is also called apparent power. Watts on the other hand, is also called true power. If the transformer feeds a resistive load, then watts are equal to VA, because the voltage and current are in phase. If the transformer feeds a reactive load, such as a motor, then the voltage and current are no longer in phase, and the true power (watts) is less than apparent power.

Since the true power, or watts delivered can change depending on the load, it is not very useful as a transformer rating. The VA remains constant irregardless of the load characteristics, and so is a much better indicator of transformer performance.

Yes and no. The initial phases of swallowing are under voluntary control, but swallowing takes several different muscles to act in a synchronized way and after initiation of the swallow, the later phases are automatic and not voluntary.

A microampere is simply one millionth (1x10-6) of an ampere.

An iron core, usually in the form of two horizontal parallel parts and three parallel vertical parts to form two 'windows'. On that core there are two coils of wire wound round the central iron part. One coil is the primary and one is the secondary.

The metal cores can look like the letter E and they are interlaced (sandwiched) l so that one faces up and the other faces down on top of each other. The wires are usually wrapped around a guide before the cores are placed in it. The wire is copper wire and it is coated with laquer for insulation because this does not take as much space as normal plastic or rubber insulation. The cores are wrapped according to whether the transformer is increasing (step up) or decreasing (step down) the voltage. Some applications require the transormer to be encased in a shell to reduce electrical noise.

Current transformer and voltage transformer . This transformers are actually measuring instruments which measures the quantity of current and voltage coming out of the substation.

somthing that sycronizes stuff in a genorator

A stair stepper can be purchased at stores such as Sears, Amazon, Brookestone, and Wal-Mart. It should also be noted that the stores mentioned are a few places that a stepper can be purchased.

Although there are many filter types and ways to implement them, here's an active low-pass filter that's greatly simplified if R1=R2 and the op amp stage is a unity gain follower (RB=short and RA=open). Designing a 2-pole Butterworth filter requires just a few steps. 1. Choose a cutoff frequency fo (Hz). As an example, select fo=10 kHz to reduce a noise signal at 50 kHz and pass your desired signals below 5 kHz. 2. Pick a convenient cap value C2 between 100pF and 0.1 uF. Suppose you've got plenty of 1000pF caps in stock, select this value for C2. 3. Make C1 = 2 x C2 C1 = 2 · C2 = 2000pF 4. Calculate R1 = R2 = 0.707 / (2 · π · fo · C2) R1 = R2 = 0.707 / (2 · π · 10kHz · 1000pF) = 11.2 K ohms ......Rajiv......(scet)

Sounds like a relay to me.

AC alternates - so the current naturally passes through zero twice very cycle. Interruption in an AC Circuit breaker takes place at one of those natural current zeros.

There is arcing during the course of interruption - dielectric strength builds up gradually as the breaker contacts physically open, and until the contacts have opened sufficiently, conduction will re-establish after the initial currents zeros. But once the contacts are open sufficiently to provide enough dielectric strength, the arc will be extinguished. The breaker mechanism may include provides to accelerate arc extinction - typical scheme include arrangements that extend and cool the arc.

DC does not alternate, so there are no natural current zeros. That implies two things. First, the physical opening of the breaker must be faster and physically greater to create sufficient dielectric withstand to extinguish the arc. That is usually what is done with smaller breaker.

But for breakers with larger electrical ratings, it may be necessary to include a provision to force an artificial current zero. One approach is to include a capacitor that is charged by the normal DC voltage, and that is inserted into the circuit as the breaker opens to oppose the normal voltage to force the current to zero.

voltage is equal to resistance multiplyed by current. you have the 2 pieces of info, just multiply

Yes!

ohms law states V = I*R; V = (.005)(1000) = 5volts.

Yes

Not necessarily. In a simple circuit V=IR, so if the resistance in a circuit remains constant, then voltage and current are directly proportional, so an increase in one will increase the other. If you were to change resistance and keep voltage constant, then the current would be inversely proportional to resistance, so as resistance went up, current would go down.

The resistor allows current to enter the electromagnet in an electric motor. The resistor regulates the amount of current that enters the electric motor.

as mechanical maintenance engineer following responsibility

1.doing preventive maintenance and keep machine condition good as possible.

2.finding machine requirement in running condition

3.attend machine breakdown and find the route course of same

4.check machine all spare parts and constable items stock as required.

The main difference is that lighting caps are required to contain a bleed resistor in parallel across the cap s terminals to drain the high voltage contained in the capacitor to safe levels (usually within a minute or so) after the equipment is switched off. Motor run caps don't require bleed resistors due to them being constantly connected to the motor windings which act like a resistor to drain the capacitor after use.

Depends on where you want to put it! Assuming, that you're asking ~how you'd "install" a Definite purpose contactor.

Speed control of any kind of motor is important because it enable the user of the motor to restrain the motor speed to the needed or required speed to accomplish a specific task. omatycoon@gmail.com

micro farad

In order to determine power from volts and amps, we need to know the power factor and efficiency, but the question did not provide that information, so I will make an educated guess that the efficiency is 0.95 and the power factor is 0.92. The actual motor nameplate ratings will have to factor into the real calculations.

460 V times 120 A is 55.2 KVA. The question did not say, but it is assumed that the 120 A is per phase, so divide by 1.732 (square root of 3) to get winding power of 31.9 KVA, and then multiply by 3 to get total winding power of 95.6 KVA. Multiply by 0.92 and 0.95 to get power in watts of 83.6 KW.

If you want to know kilowatt-hours for 30 days, multiply by 30 and 24 to get 60.2 mega watt-hours.