Electrical Engineering

over speed control is recommended for all prime mover driven generator to prevent over frequency operation of load connected to a system supplied by the generator and also to prevent possible over frequency operation of the generator itself from Ac system.

CA type breakers are designed to meet California's specific electrical codes, while BR type breakers are more commonly used in other states. In terms of compatibility, CA type breakers are typically not interchangeable with BR type breakers due to differences in design and specifications. It is important to use the appropriate type of breaker based on your location and electrical system requirements.

No, using two single phase surge protectors in place of one three phase surge protector is not recommended. A three phase surge protector is specifically designed to protect all three phases of a power system simultaneously and provide comprehensive protection. Using individual single phase surge protectors may leave some phases vulnerable to surges and compromise overall protection.

DC (direct current) flows in one direction only, while AC (alternating current) changes direction periodically. DC is commonly used in batteries and electronic circuits, while AC is used in household electrical systems because it can easily be converted to different voltages using transformers.

In principle you can use a common wire for ac and dc in a low voltage low power circuit, for example 12 volts at up to about 20 watts. If the ac is at a power-supply voltage it must use separate wiring to comply with safety standards.

In low-power dc equipment like radios it is normal to use a step-down transformer with the ac live and neutral connected to the primary, and the earth connected to the transformer case, the chassis and one side or other of the dc supply taken from the secondary via a rectifier and smoother.

Fully loaded - 2.62 amps at 11kV. The no load depends on the transformer design, but it will usually be significantly less than the full load amps (not sure on this size, but on larger transformers it is typically ~.05 - .1% full load, so you'd be looking at ~2.5 mA RMS).

The connection type is not important. Transformers are very efficient, thus there is not a whole lot of loss in the "average" transformer. The actual loss will depend on the design criteria of the transformer.

There are two ways: If the amps are the same on all three phases (voltspp is the phase to phase voltage): amps * voltspp * 1.73 = watts If the amps are different on each phase (voltspn is the phase to neutral voltage): (ampsA + ampsB + ampsC) * voltspn = watts In a 480V system, 480 is phase to phase and 277 is phase to neutral, likewise 208/120, etc. Example - 12A on all phases, 480/277V system: 12 * 480 * 1.73 = 9965W Example - phase A = 4A, phase B = 6.3A, phase C = 2.2A, 208/120V system: (4 + 6.3 + 2.2) * 120 = 1500W

Yes, but it would have to be a pretty big and expensive wind generator. You would need an inverter to produce at least 500 watts of 3 phase power. Unless you also had some big batteries, you could only run your motor when the wind is blowing!

To calculate three-phase meter reading in kWh with CT coils, you need to first determine the current ratio provided by the CT coils. Multiply the current readings obtained from the CT coils with the current ratio to get the actual current values. Then, multiply the actual current values with the voltage and power factor to get the power in each phase. Finally, sum the power in each phase and multiply by the time in hours to get the kWh reading.

The correct spelling is 'brake' rather than 'break', but the 'drum' you refer to is used when testing the output power at the shaft of an induction motor. The diameter will depend on the power of the motor, and the test equipment used. 'Brake power' refers to the output power of the machine measured in watts or, in the United States, in horsepower. If you know the output power (by conducting this test) and the input power (using a wattmeter), then you can determine the machine's efficiency.

No, a single-phase supply cannot be directly used in a three-phase system. The voltages and phases are different, so additional equipment such as a phase converter or transformer would be needed to convert the single-phase supply to match the requirements of the three-phase system.

Yes, just splice a potentiometer (dimmer knob) in series and it should work just fine. In fact they are a lot more energy efficient at just a little below max output, and look just as bright.

The resistance R in ohms (Ω) is equal to the voltage V in volts (V) divided by the current I in amps (A)

ohms law.

no

Ohms law does not consider inductance

Current

There are 1,000 terawatts in one gigawatt. This is because one terawatt is equal to one trillion watts, and one gigawatt is equal to one billion watts.

For questions of this type, it seems the main issue may be one of definitions and industry terms. See if this makes sense:

Line voltage is a very ambiguous term. For instance, say you are wiring a doorbell transformer. You feed 120V into the primary, and 18V comes out the secondary. The electrician would say the output is "low voltage" and the input is "line voltage". He simply means the building wiring, or "lines". Now, if you go out to the breaker panel, you will measure 120V from each "leg" to neutral, but you can also measure 240V from leg to leg. It's all line voltage. Line voltage simply means the voltage present in that particular power distribution system.

Now the power in your house is "single phase" (well, in almost all homes, anyway). Single phase is fine for most anything, but motors are a special case. Motors need something to create a rotating magnetic field to get them turning. Single phase power doesn't have anything to do that, so they need some sort of a gimmick, like a capacitor, to create a "phase shift" to get the rotation.

Single phase AC (alternating current) simply means the voltage goes positive then back down to zero, then negative then back up to zero. That's one complete cycle. The cycle is divided into 360 degrees, like a circle. The positive voltage goes from 0 to 180 degrees, and the negative half 180 back to 0.

Now 3-phase power has, you guessed it, 3 hot wires. Each hot wire, when paired with a neutral, is a single-phase source. Heres the big difference: Phase A starts its positive cycle. When it is 120 degrees into the cycle, phase B starts going positive. When Phase B is 120 degrees finished with its cycle, phase C starts going positive. When phase C is 120 degrees into its cycle, that's a total of 360 degrees, and phase A is done with one cycle, and the whole process starts over. Picture 3 people doing "the wave" at a football game. Same principle.

This time difference, or "phase shift" is what makes 3-phase power unique. 3-phase motors use the phase shift directly to produce the rotating magnetic field they need to turn. Think of 3 people in a circle, tossing a ball around. see the "circular" motion? Now picture two people tossing the ball back and forth. No circular motion there. That's the difference between single-phase and 3 phase.

So, electricians use the term "phase" to refer to one of the three hot wires in a 3-phase (also correctly called multiphase or polyphase) power system. The term "phase" voltage is just as ambiguous as "line" voltage. To be accurate, you must specify whether you mean phase-to-phase voltage, or phase-to-neutral voltage.

Confused? if you go into a large commercial building with 3-phase power, many times the incoming panel will have voltmeters on the front. In one building, the first meter will be labeled "phase-to-phase voltage", and the second meter will be labeled "phase-to-neutral voltage". Go into the building NEXT DOOR, and the same meters will be labeled "line-to-line voltage" and "line-to-neutral voltage". See? the terms are used pretty interchangably.

In a 3-phase system, each phase, leg, or line has the same potential, or voltage (except for a very few wierd and pretty outdated systems). If you measure from phase A to Phase B you will get the same reading as B to C, also the same as C to A. So, measuring any two phases will tell you what the line voltage is, but that motor still needs all 3 phases to get the rotation.

To understand the different voltages you find in a 3-phase system, see the related questions for another answer that relates to that subject.

You'll need to control the motor with a large, three-pole relay, called a "contactor". If the motor is of significant size, you'll need a special kind of contactor called a motor starter (or motor protector). This is a current-protected contactor with current-based heaters sized appropriately for the motor load. They allow for the high starting currents typical of inductive motor loads and provide protection at lower currents as the motor runs.

Contactors and motor starters will have a coil voltage that's typically 24VAC, 120VAC or 208VAC. That control voltage will be switched through the single pole, normally open points of the time clock. All electro-mechanical time clocks will be able to deal with most any control voltage. Some newer solid state time clocks may not be rated to 120VAC or 208VAC so you'll need to verify the control voltage of one when deciding on the other.

A number of companies in the U.S. make contactors and motor starters: Cutler Hammer, Allen Bradley (Rockwell) and Square D are a few well known brands in the States. Other manufacturers (Siemens, et al) are more prevalent in other countries. Check with an industrial electrical supply or commercial equipment and motor supply like W.W. Grainger.

An inverter is the apparatus that changes direct current (DC) to alternating current (AC). It does this by converting the fixed voltage and direction of DC electricity into an oscillating voltage and alternating direction of AC electricity.

No, single-phase 200V from Japan cannot be directly used with two-phase 120V/240V in the US. The voltage and phase differences between the two systems make direct compatibility impossible. A voltage converter or transformer would be needed to convert the electrical supply to match the requirements of the equipment.

For a 37 kW induction motor, a cable size of approximately 10 AWG (American Wire Gauge) would be suitable for typical installations. However, the specific cable size required would depend on factors such as the length of the cable run, ambient temperature, and voltage drop considerations. It is recommended to consult with a qualified electrician to determine the appropriate cable size for your specific application.

The reading on the 3-ph meter would equal the sum of the three separate readings on the single-phase meters.

The neutral sides of the single phase meters do not need to be connected to the neutral wire as long as they are connected together.

Yes, there is a control knob on the gen-set that will have a label called field excitation or just field. Look at the volt meter and turn this control in a clockwise direction. The voltage should increase as you turn the control.