Alternating current refers to the current that changes periodically at any time and direction, and the average current in a period is zero. Unlike direct current, its direction changes with time, while direct current does not change periodically. Usually, the waveform of alternating current is sinusoidal. Alternating current can effectively transmit electricity. But there are actually other waveforms, such as triangle wave and square wave. The commercial power used in life is sine wave alternating current.
When electromagnetic induction was discovered, the method of generating alternating current was known. The early generators were invented by michael faraday, an Englishman, and Puzhengsu Percy, a Frenchman. 1882, British electrician James Gordon built a large two-phase alternator. Lord Kelvin and Sebastian ziani de Ferranti developed early alternators with frequencies ranging from 100 Hz to 300 Hz. ?
189 1 year, nikola tesla obtained the patent of high frequency alternator (15000Hz). 189 1 year later, power supply will be provided by multiphase alternator. Thereafter, the AC frequency of the alternator is usually designed between 16 Hz and 100 Hz, and it is used in conjunction with arc lamps, incandescent lamps or motors. ?
According to the law of electromagnetic induction, when the magnetic field around a conductor changes, an induced current will be generated in the conductor. Usually, the rotating magnet is called rotor, and the fixed group in the coil with conductor wound on the iron core is called stator. When it passes through a magnetic field, it generates an electric current. The basic machine that generates alternating current is called alternator.
The difference between alternating current and direct current
Alternating current and direct current are two common current forms, which are obviously different in the direction, nature and application of charge flow.
1, flow direction:
Alternating current: Charge flows alternately in positive and negative directions periodically.
Direct current: the charge flows continuously in one direction.
2. Voltage change:
Alternating current: the voltage changes in the form of periodic sine wave, and the amplitude changes from positive to negative and then to positive.
Direct current: the voltage remains constant and does not change periodically.
3. Charge properties:
Alternating current: The magnitude and direction of electric charge change with time.
Direct current: the magnitude and direction of charge remain unchanged.
4. Transmission distance and loss:
Alternating current: Alternating current can be efficiently transmitted through transformer, which is suitable for long-distance transmission. However, there will be some resistance loss during transmission.
Direct current: Direct current will have a large energy loss when it is transmitted over a long distance, so it is not suitable for long-distance transmission, but the loss is small in a short distance.
5. Application areas:
Alternating current: Alternating current is widely used in household, industrial and commercial electricity, transportation, communication and other fields.
Direct current: Direct current is commonly used in electronic equipment, battery power supply, photovoltaic power generation and electric vehicles.
It should be noted that many electronic devices and power systems need to convert alternating current into direct current, and vice versa. Energy conversion is carried out by using transformers, rectifiers and inverters.