# Power and frequency relationship

### Utility frequency - Wikipedia

electric power is the rate at which electrical energy is transferred by an electric circuit the rate per second of a vibration constituting a wave either in a material as . AC frequency is the number of cycles per second in an alternating current (AC) sine wave. Power line frequency (normally 50 Hz or 60 Hz). Variable-frequency . Usually the first step on any power supply designer's checklist is to choose an appropriate Increasing the operating frequency can reduce the size of these.

This conductor provides protection from electric shock due to accidental contact of circuit conductors with the metal chassis of portable appliances and tools. Bonding all non-current-carrying metal parts into one complete system ensures there is always a low electrical impedance path to ground sufficient to carry any fault current for as long as it takes for the system to clear the fault.

### Relationship between frequency and power - Electrical Engineering Stack Exchange

This low impedance path allows the maximum amount of fault current, causing the overcurrent protection device breakers, fuses to trip or burn out as quickly as possible, bringing the electrical system to a safe state. AC power supply frequencies[ edit ] Further information: A low frequency eases the design of electric motors, particularly for hoisting, crushing and rolling applications, and commutator-type traction motors for applications such as railways.

However, low frequency also causes noticeable flicker in arc lamps and incandescent light bulbs.

The use of lower frequencies also provided the advantage of lower impedance losses, which are proportional to frequency. Effects at high frequencies[ edit ] Play media A Tesla coil producing high-frequency current that is harmless to humans, but lights a fluorescent lamp when brought near it A direct current flows uniformly throughout the cross-section of a uniform wire.

Reactive power and voltage relationship in power transmission line

An alternating current of any frequency is forced away from the wire's center, toward its outer surface. This is because the acceleration of an electric charge in an alternating current produces waves of electromagnetic radiation that cancel the propagation of electricity toward the center of materials with high conductivity.

## Electric power and frequency, what is the relationship between them?

This phenomenon is called skin effect. At very high frequencies the current no longer flows in the wire, but effectively flows on the surface of the wire, within a thickness of a few skin depths.

For example, the skin depth of a copper conductor is approximately 8. Since the current tends to flow in the periphery of conductors, the effective cross-section of the conductor is reduced.

This increases the effective AC resistance of the conductor, since resistance is inversely proportional to the cross-sectional area. The AC resistance often is many times higher than the DC resistance, causing a much higher energy loss due to ohmic heating also called I2R loss.

Techniques for reducing AC resistance[ edit ] For low to medium frequencies, conductors can be divided into stranded wires, each insulated from one another, and the relative positions of individual strands specially arranged within the conductor bundle.

• Utility frequency

Wire constructed using this technique is called Litz wire. This measure helps to partially mitigate skin effect by forcing more equal current throughout the total cross section of the stranded conductors. Litz wire is used for making high-Q inductorsreducing losses in flexible conductors carrying very high currents at lower frequencies, and in the windings of devices carrying higher radio frequency current up to hundreds of kilohertzsuch as switch-mode power supplies and radio frequency transformers.

Techniques for reducing radiation loss[ edit ] As written above, an alternating current is made of electric charge under periodic accelerationwhich causes radiation of electromagnetic waves. Energy that is radiated is lost. Depending on the frequency, different techniques are used to minimize the loss due to radiation. This reduces losses from electromagnetic radiation and inductive coupling.

A twisted pair must be used with a balanced signalling system, so that the two wires carry equal but opposite currents.

Each wire in a twisted pair radiates a signal, but it is effectively cancelled by radiation from the other wire, resulting in almost no radiation loss. Coaxial cables[ edit ] Coaxial cables are commonly used at audio frequencies and above for convenience.

A coaxial cable has a conductive wire inside a conductive tube, separated by a dielectric layer. The current flowing on the surface of the inner conductor is equal and opposite to the current flowing on the inner surface of the outer tube. The electromagnetic field is thus completely contained within the tube, and ideally no energy is lost to radiation or coupling outside the tube.

Coaxial cables with an air rather than solid dielectric are preferred as they transmit power with lower loss. Waveguides[ edit ] Waveguides are similar to coaxial cables, as both consist of tubes, with the biggest difference being that the waveguide has no inner conductor. Waveguides can have any arbitrary cross section, but rectangular cross sections are the most common.

## Alternating current

Because waveguides do not have an inner conductor to carry a return current, waveguides cannot deliver energy by means of an electric currentbut rather by means of a guided electromagnetic field. R of the heater doesn't change. Many US wall clocks will run slow in Australia. They are synced to the very accurate 60Hz of the power system.

### Relation between frequency and power | CrazyEngineers

Today nearly all electronics use "switching" power supplies and take a very wide input. They have become very efficient and small. Most things with large motors or lots of power will still be specialized. Towne Springer May 1 '14 at 4: In terms of eddy current lossesthey increase with f for same power density slightly. For long haul DC is best.

There is no advantage to use 50 or 60Hz power systems in general but specific components may have preference. But Aircraft prefer much higher f, for lower mass generators. I'm not too sure about what my question was, im amazed at how much detail everyone has gone into! I'll take some time to have a look and try to understand what everyone is saying and see if it helps my understanding, thanks everyone!

Overall, the benefits and disadvantages of 50 - 60 Hz relative to each other probably do balance out.