Electrical Wiring

Bodies directly surrounding the body (Penn Foster)

A: They are both the same the first is the product volts times amperes the second is related to volts and amperes also. The difference is the second term is used to rate transformers power output in terms of voltage to amperes. Example a 1kva means that you can expect 1kv at 1 ampere on the transformer output . But here is the trick the transformer only put out 250 volts So now what It means is 250v at 4 amperes nothing has changed the power remains the same 1 kw

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To convert KW to KVA just leave the power factor (pf) out of the equation.

Formula for Kilowatts = I x E x pf/1000.

Formula for KVA = I x E /100.

The usual supply in Russia is 220 v 50 Hz which corresponds to a 3-phase supply of 381 v. You need to check your motor to see what voltage range it is designed for, but 381 v is only 4.8% low so it should be all right.

To make any electrical circuit work it has to be complete. Source of power to the load, the load itself and a return path from the load back to the source. The source in this case being the distribution panel. Any breaks in this complete path will cause the current to stop flowing and the device to not work. A light fixture and light switch work on this principle, open the circuit and the light goes out.

90 kW on 480 volts single phase would be 187.5 amps. On 480 v 3-phase it would be 108 amps.

In order to convert from single phase to three phase, you need an inverter or some kind of motor-generator.

Variable Frequency Drives for electric motor speed control now feature single phase input with three phase output for motor loads up to 3HP. Good for the home shop where you got a deal on some equipment but lack 3 phase power. For instance, Google this: ATV12H075F1

Buy either a phase convertor or motor-generator with the proper input and output ratings. Essentially you have to generate your own 3-phase power using the 220V as the energy input. There is no wiring or connection scheme that will directly do this.

A single wattmeter can measure power due to one phase only. But circuit arrangements , popularly called:

1) 2-wattmeter method (requiring two wattmeters)

2)3-wattmeter method (requiring 3 wattmeters)

can be used for measuring power inn 3-phase circuit. The details of these method can be found in any standard book on electrical engineering.

AC motors are not suitable for tape recorders because the speed can not be kept sufficiently constant. Tape recorders use dc shunt-wound motors with electronic speed control.

You use a megger. This allows you to check what the condition of the insulation of the motor windings are. An ohms check on each phase should be an easy way if it reads OPEN then there's your bad phase. Otherwise there are diffrent types of 3 phase motors, could be the brushes, commutator, sliprings, many many things.

Switching any two of the three phases will cause the motor to turn in the opposite direction. This rotation change should be done in the motor's junction box so that the colour phasing will remain accurate throughout the circuits system. For that reason, motors used where the direction of travel matters (like for elevators or escalators) are equipped with reverse phase relay devices that prevent the motor from operating unless the phases are wired in the correct order.

Switch two leads of the wires going to the motor for ex. L1,L2,L3 change to L1,L3,L2.

If this motor is wired for wye-delta starting, it will be easier to change the incoming power than at the motor junction box. Wye delta motors are six lead or twelve lead motors and lead pairing is critical on a wye delta setup. If the motor is started across the line like a standard nine lead motor, then by all means change it at the motor junction box.

This could be dangerous if you aren't very careful. Take the transformer out of the welding machine. Put it on a wooden bench. Apply 12 volts to the input side with a car battery. Measure the input volts with a volt meter and write down the value. Then use your volt meter to measure the output voltage. If you have no output voltage then your transformer is obviously blown. You should read an output voltage that is higher than the input voltage based on the number of winding in the coil and/or the manufacturers specifications. According to Faraday's law the only output voltage you will read is at the exact time power is applied to or taken away from the input when using dc power. Otherwise you will have to apply ac power which is much more powerful ( and more dangerous ) than the 12v dc. Your volt meter may not be designed to read high enough voltage for the output you would see with 110 v ac.

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 generators, motors, machines and appliances that use lots of power. If the application is large power, or small power with weight restrictions (like automobiles!) Three Phase is preferred. 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 be transformed down to safer, much lower mains voltages for use by consumers.

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.

The resistance of a forward biased pn junction is zero.

Incoming power goes through the main breaker to the lugs feeding all branch breakers/fuses. Shutting off the main breaker shuts off power to all other breakers/fuses downstream.

This may not match with NEC's definition. You should check that too.

under voltage relay is used to protect the electrical equipment from the low voltage below the rated voltage till 80% of the network potential.

u/v relay is used to give a signal to emergency generator to start whenever the system voltage drops below (80%).

U/V relay number is (27) which is available in most electrical circuits to protect the following circuits by insulating them whenever the low voltage occurs:

LV/MV switch boards.

Motor feeders

Generator Circuits

Transformer circuits

u/v relay is considered to be one of the main protective relays in electrical design.