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This is because the phase angles are almost 90 degrees apart between the voltage and the current. Since the power is the product of these two almost 90 degrees out of phase sinusoidal waveforms - any phase angle error will result in a much higher error than two sinusoidal signals that are shifted by a much smaller angle. Therefore the phase angle errors in all the instrumentation (Voltage and Current transformers) will contribute far more to errors for low power factors.

If you wan ...

Every motor type (synchronous, squirrel cage and wound rotor induction, direct current, permanent magnet, linear, switched reluctance, etc.) all have a "sweet spot" in terms of efficiency. Some are designed to work well at low- to moderate-power ratings and high speed; others are best suited for high-power and slow speeds.

Most low-power motors are designed to operate against fairly simple load torque profiles; this means they can be optimized quite readily because there isn't much ...

If you operate a 3600 rpm (60 Hz) synchronous generator at 3000 rpm (50 Hz), the power output will be reduced, simply because the mass of the rotor remains constant and you reduce its rotational speed. Based on the laws of physics, kinetic energy is directly proportional to the mass and the square of the velocity. Conversely, if you operate a 3000 rpm (50 Hz) generator at 3600 rpm (60 Hz) the power output wi ...

Electromagnetic Interference (EMI, also called radio-frequency interference or RFI when in radio frequency) is a disturbance that affects an electrical circuit due to either electromagnetic induction or electromagnetic radiation emitted from an external source.

All motors create magnetic fields because of the currents passing through the windings - or just because they have strong magnets (permanent magnet designs). Stronger magnets will create stronger fields - which will extend t ...

All electrical equipment has a definite life span and its replacement depend upon the manufacturer's advice. However I would advise periodic inspection to see the condition of the relay or contactor such as condition of the coil if its visible from outside, including any testings if required; the condition of the contacts, to see they are clean, carbon and rust free, and in good contact or in open position as the case may be; and the connection of the wires to the terminals and the terminal t ...

Allowable current density is not a random choice. It is directly related to the temperature of the conductor and is dependent on the insulation (on the individual strand, on the turn, and on the completed coil), the method and efficiency of the cooling, the heat transfer properties of the surrounding magnetic materials, and the nature of the current itself (AC or DC).

As a really rough approximation, a current density of 3000 ampere / mm^2 equates to something like a temperature ri ...

The purpose of a generator set is to transform the energy in the fuel used by the prime mover into electrical energy at the generator terminals. Since nothing is perfect, the amount of energy input is ALWAYS greater than the amount of energy output, resulting in an efficiency that is ALWAYS less than 100 percent.

Every fuel has a basic "heat value": this is usually broken down into two cases. The first case uses a LOW value that corresponds to the assumption where the water vapor c ...

In a single phase AC motor (at starting) there is only one pulsating field. For the sake of analysis only it could be represented by two rotating fields of equal magnitudes and rotating in opposite directions. If the rotor of this single phase motor is moved by any means, the stator field is still a pulsating field but the rotor induced currents will produce a rotating field and for the sake of analysis this rotating field is added to the component of the stator field rotating in the same dir ...

When using a standard DOL (direct on line starter), star delta starter or even n liquid starter standard bearings in the motor is not a problem. When using a Soft Starter or VFD it is recommended that bearings are insulated. This is to prevent rotor/bearing racking which could result in a direct short. But in the event where a none insulated motor is available it could be used as a short term option. Unfortu ...

Grounding of a generator is required for two reasons. Firstly you will need to gain a reference for your voltage. You may get 380v between phases and 220v to neutral but if the neutral starts to float due to ground surges or induced voltages with in the ground, your voltage to earth may rise above the insulation levels of your system, especially electronic items. This can happen normally but extremes when lightning is around. Secondly, there will be no earth fault path so the first earth faul ...

A rotating machine with either better-quality materials in terms of its "active" components (lamination steel and conductors) OR better understanding of the design OR both will generally have a higher electrical efficiency for the same power/speed/volt combination. Better-quality materials for mechanical interaction (brushes, bearings, seals, etc.) will also act to improve electrical efficiency.

Alternatively, adding more "active" material to a specific power/speed/volt design can ...