this always used in inverters and UPS As in standby UPS And line interactive UPS ,the output frequency must be always track the input frequency as it supply the load from utility in standby mode, for any change that will affect the load .
as example the frequency of the utility was with permitted values say 58Hz and suddenly the main power cutout, so UPS must be on same frequency so when convert to backup stored power mode ,the load doesn't affected and power continue to supply the load from the batterys through inverter , so output frequency must be always synchronized to utility frequency (mains) in case of any fault happened, hope i answered your question.
Sherif Salah
R & D Engineer at Arrow Electronics
twice the input frequency
There are several methods for generating FM signals but they all basically involve an oscillator with an electrically adjustable frequency. This type of oscillator uses an input voltage to affect the frequency of its output. For example, when the applied voltage increases, the oscillator output frequency increases and when the applied voltage decreases, the oscillator output frequency decreases as well. If no voltage is applied to the oscillator its output will be a signal at its centre frequency. The amount of frequency variations is deviated around the oscillators' centre frequency.
Frequency response is the measure of the frequency of the output a device gives in response to a stimulus that it receives. The frequency response is a characteristic of the device.
The transition frequency of a transistor is the frequency in which the transistor will no longer provide any amplification or gain output. The frequency is out of the transistors's range.
A PLL is different than a VCO. Each has its own use. Actually a PLL (Phase Locked Loop) contains a VCO (Voltage controlled oscillator). A VCO is an oscillator whose frequency is related to an input voltage. You can use it when you need a varying frequency that is controlled by a varying voltage. But it is not great at outputting a consistant exact voltage because it is very sensitive to its environment (e.g. temperature). A PLL will "lock" its output frequency to some input frequency. So it can oscillate at a frequency that is controlled by an input oscillator. Not too useful if the output frequency is the same as the input. But the output frequency can be divided before it is compared to the input. This allows the output frequency to be higher (some multiple of) the input frequency. Once a PLL is "locked on" to an input frequency it can be very stable.
The mains voltage is 230 volts, and the frequency is 50Hz.
no
The standard AC mains in India is 230V/50 Hz .
The mains supply in Scotland is 50Hz.
50Hz
no
The mains voltage in Cyprus is 230 volts at a frequency of 50 Hz.
It depends on the rectifier. For a half-wave, it's the same as the AC mains: i.e. 60 Hz mains gives 60 Hz ripple. For a full-wave or a bridge, it's twice the AC mains: 60 Hz mains gives 120 Hz ripple. Three-phase systems are more complicated, so you would need to check in an electrical engineering book.
It depends on the rectifier. For a half-wave, it's the same as the AC mains: i.e. 60 Hz mains gives 60 Hz ripple. For a full-wave or a bridge, it's twice the AC mains: 60 Hz mains gives 120 Hz ripple. Three-phase systems are more complicated, so you would need to check in an electrical engineering book.
twice the input frequency
According to the Wikipedia article on mains electricity by country, the power in the UK operates at 50Hz. There is a link below to the article.
Audio output frequency is that range of frequencies that can be heard. For humans, that is generally considered to be the range of 20Hz to 20kHz.