In , German physicist Heinrich Rudolf Hertz Feb, to Jan-1, , the first person confirmed the existence of radio waves, and had a great contribution in Electromagnetism, so the SI unit of frequency Hertz is named as his name.
Hz Hertz is the frequency unit of the vibration cycle time of electric, magnetic, acoustic and mechanical vibration, i. This unit is also used for measuring and describing the signal bandwidth.
The EM wavelength of 1 kHz signal is km, which is about miles. Standard amplitude modulation AM broadcast bandwidth is in the range of kHz to kHz. Some EM transmissions are in millions of kHz. Log in. Install the app. Contact us. Close Menu. Welcome to EDAboard. To participate you need to register. Registration is free.
Click here to register now. Register Log in. JavaScript is disabled. For a better experience, please enable JavaScript in your browser before proceeding. You are using an out of date browser. It may not display this or other websites correctly. You should upgrade or use an alternative browser. Thread starter Gundam Start date Oct 31, Thank you. Disclaimer: Whilst every effort has been made in building this calculator, we are not to be held liable for any damages or monetary losses arising out of or in connection with the use of it.
This tool is here purely as a service to you, please use it at your own risk. Full disclaimer. Do not use calculations for anything where loss of life, money, property, etc could result from inaccurate calculations. Let's first have a quick look at the different sections beginning with the switching inverter section. C1 and C2 are charged in series from the single phase V mains through the diode bridge to a total of about V which is divided equally among both of them.
There is no power factor correction so this design is really only suitable for relatively small loads. A couple of resistors of equal value in parallel with C1 and C2 assure the voltage is distributed equally among both capacitors. I happened to have K but I probably would have chosen a somewhat lower value like K.
An NTC limits the inrush current. I also added a fuse to the inverter section which is not shown in the diagram at the line input. This is common sense and the only protection against overloads. The load is connected on one end to the middle point of C1 and C2 and the other end is alternatively switched between the high and low rails by the half bridge formed by TR1 and TR2. This is to protect from transients due to inductive loads.
I mounted the pair of transistors on a radiator although with the reduced load they hardly warm up but the inverter circuit could be upgraded to handle greater power by just increasing the value of C1 and C2 and transistor heat would not be a problem.
This is the good part of working at a low frequency such as 50 Hz, 60 Hz. Peak value is important for devices which charge capacitors to peak value and RMS is important for other devices. For this reason this waveform is the best rectangular approximation to a sine wave and is commonly called "modified sine wave".
I, personally, dislike this marketing term because it is quite inaccurate. Rectangular wave or "modified square wave" would be more accurate. Some devices might require true sine wave from the frequency converter. Many voltmeters measure average volts and correct by a factor of 0. Such an instrument when measuring a rectangular "modified sine wave" like this one will under-indicate by a factor of 0. Waveform True sine Modified Sine Peak 1.
Actual voltage from the mains have the top very much clipped due to all the rectifier-capacitor loads. TR1 called "low side" is easy to control because the source is at the same base reference level as the controlling circuit but TR2 called "high side" is a bit more tricky because it is floating and goes all the way between both rails.
There are many ways to solve the problem of translating the level of the control signal. You can search for "high-side control" or similar terms. There are many discrete circuits and integrated solutions.
I considered using a IRS for simplicity but it was relatively expensive and difficult to find so I decided to go with my own discrete solution using an old optocoupler which I already had.
The design is extremely simple and works well at 60 Hz but would not be suitable for high switching frequencies because TR2 delays in switching off and the circuit would have to be altered to make it switch off faster which would not be complicated to do. This is because the gate discharges through the capacitor rather than having a signal forcing it down. Change the value of the resistor speeds up the switch-off time but requires higher current while the transistor is turned on.
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