Recently I was thinking about a generator project and realized that is beyond my current understanding of AC power. I have been doing some research since but I am really having a hard time understanding the frequency part of AC power sources. From what I understand the frequency of an AC signal is the number of full +/- voltage cycles in a signal.
To make discussion simpler lets consider an A/C generator that is driven by a constant 1500 RPM. If that generator has has 4 poles this would result in 50 Hz, since there are 6000 magnet switches every minute, which is 3000 full voltage changes a minute which is 50 changes a second.
Now lets assume I have the same sort of generator (size, etc) but it has 12 poles like an usual car alternator, it will produce 150Hz AC power. At this point I am really wondering why any appliance would care. If you consider it within a full second nothing really changes, there is the same amount of time in positive voltage and negative voltage as if it would be running with 50Hz. It just switches three times more often.
Why exactly do A/C appliances care how often the voltage inverts with A/C power sources?
So an induction motor designed to run on 60Hz will run slower on 50Hz. This isn''t usually a problem as this essentially de-rates the motor. On the other hand, running a 50Hz motor on 60Hz might be a problem as the motor can deliver more power than it''s designed for.
Universal motors won''t care.
Appliances that internally convert AC to DC (including home computers and other electronics) won''t care, mostly. Power supplies that support 50Hz need more input capacitance than 60Hz ones.
IT gear power supplies have largely migrated to designs that support all worldwide line voltages and frequencies, so they''re designed specifically to not care. Specifically, they have bigger capacitance rated at higher voltage to accommodate both 50Hz and 230/240V as they are rectified to DC.
Magnetic iron cores are rarely efficient at spanning over a decade or maybe 2 of frequency unless ferrite. So automotive alternators are not as efficient as fixed f types. Eddy current losses tend to increase exponentially with frequency and Z also increases with f until self winding parallel resonance (LC).
200 to 400 Hz magnetics in iron cores have thinner laminates and ferrites also change composition with RF frequency with lower mu and more conductive particles. So the big torroids once used in audio power amps or SMPS are high mu until they start to exceed a certain f.
The main problem with magnetics and high current is if you lower the frequency too much, they can saturate and turn into resistors, so V/F ratios are used in variable speed motor AC controllers.
Read the appliance label near cordset for safety approvals.
DC flows in one direction. Alternating Current goes forwards, then goes backwards. The rate at which it flows back and forth is it''s frequency, ie. how often it flows in a direction.
Some devices rely on this frequency to control power, motor speed, calibrate, etc. ie device operations. Utility supply frequency eg. 60 Hz is very low for high precision devices eg. computers, so they have their own oscillators to do the job, mostly quartz crystals that run in MHz. In this case the AC supply just gets converted, or rectified to DC just to power the device.
Any device that runs on DC doesn''t rely on power supply frequency, when powered by AC mains adapter, or charger. One instance though, this frequency would matter a little in this case is on the efficiency of the power supply, since reactance and impedance wastes energy, just like resistance in powered loads, and is based on quality of components inside the power supply, specifically capacitors and inductors.
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The supply frequency of an AC circuit refers to the number of complete cycles of alternating current that occur per second. It is measured in Hertz (Hz) and is typically 50 or 60 Hz for most household and industrial circuits.
The supply frequency can be calculated by dividing the number of cycles of alternating current by the time taken for those cycles to occur. This can be measured using an oscilloscope or a frequency meter.
The supply frequency of an AC circuit is primarily determined by the power grid and the generator used to produce the electricity. However, factors such as load on the circuit, changes in voltage, and changes in frequency can also affect the supply frequency.
In most cases, the supply frequency of an AC circuit cannot be changed as it is determined by the power grid. However, some specialized equipment, such as frequency converters, can be used to change the frequency for specific applications.
If there is a mismatch between the supply frequency and the equipment''s required frequency, it can cause damage to the equipment or affect its performance. It is important to always ensure that the supply frequency matches the frequency requirements of the equipment being used.
Although single-phase power is more prevalent today, three-phase is chosen as the power of choice for many different types of applications. Generators at power stations supply three-phase electricity. This is a way of supplying three times as much electricity along three wires as can be supplied through two, without having to increase the thickness of the wires. It is usually used in industry to drive motors and other devices.
Three-phase electricity is by its very nature a much smoother form of electricity than single-phase or two-phase power. It is this more consistent electrical power that allows machines to run more efficiently and last many years longer than their relative machines running on the other phases. Some applications are able to work with three-phase power in ways that would not work on single phase at all.
Mind you, since three-phase electricity is rarely used for domestic purposes, the table below is only relevant to electricians, electrical engineers and other technically skilled people. Travellers and laymen should take a look at the single-phase voltage table.
Alternating current (ac) frequency is the number of cycles per second in an ac sine wave. Frequency is the rate at which current changes direction per second. It is measured in hertz (Hz), an international unit of measure where 1 hertz is equal to 1 cycle per second.
At its most basic, frequency is how often something repeats. In the case of electrical current, frequency is the number of times a sine wave repeats, or completes, a positive-to-negative cycle.
The more cycles that occur per second, the higher the frequency.
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