Hi!
I want some hint or idea regarding how to vary frequency of AC 250V 50 Hz input. I want to generate 250V AC with variable output frequency. I need some solid state solution. Please help me...
Varying AC frequency
Re: Varying AC frequency
Hi Dale!
Frequency anything from 5Hz to 50kHz.
Current ~ 50 Amp<p>Sunil
Frequency anything from 5Hz to 50kHz.
Current ~ 50 Amp<p>Sunil
Re: Varying AC frequency
Waoh, 250V, 50A at 50Khz, that would be a challenge. That is 12.5kW at almost RF frequency!<p>How about a generator with a variable speed engine driving it. In a simple AC generator the frequency is essentially the speed of rotation. I don't think you could get quite the frequency range you want though.<p>If that aint anough, look into gov't surplus radio broadcast or radar equipment and truck mounted power systems.<p>For lower voltage, current and bandwidth, I would suggest a function generator driven into an audio amplifier. 200W would get you about 40V, 5A through a 8ohm load. An automotive amp would be well suited for this especially with bridgable outputs.
Re: Varying AC frequency
Not to discourage Sunil, but that's 10 octaves of frequency range! AND at 50 amps! Hope you have deep pockets for this project.
Could we ask what it is for, in case theres an alternative possibility to achieve your goal?
Could we ask what it is for, in case theres an alternative possibility to achieve your goal?
WA2RBA
- Chris Smith
- Posts: 4325
- Joined: Tue Dec 04, 2001 1:01 am
- Location: Bieber Ca.
Re: Varying AC frequency
You probably mean 5 to 50 Hz? <p>In that case its not that hard. <p>Do get back?<p>50 Kilo Hz is RF,.... and also the absorbing mechanism of any kind, other than a open antenna, would have much trouble keeping up with the load impedance match of that magnitude.
Re: Varying AC frequency
Thanks all for your kind suggestions. I am really very sorry for mistakenly typing 5Hz to 50 kHz, in fact Chris Smith is right. I mean 5 Hz to 50 Hz. Now please suggest is there any solution for getting it. I want to convert an input 250V 50A (Max) 50 Hz AC to 250V 50A AC at desired frequency in range 5Hz to 50Hz. I don't want to use any electromechanical system like generator and looking for only solid state devices. The frequency I want to vary is as per input data in real time domain. Take it in this way that I want to frequency modulate and demodulate my input data on 250V 50 A similar to FM, where the freq. variation range should be 5Hz to 50 Hz.<p>Hope to get some useful resonse now..
regards,
Sunil
regards,
Sunil
- Chris Smith
- Posts: 4325
- Joined: Tue Dec 04, 2001 1:01 am
- Location: Bieber Ca.
Re: Varying AC frequency
I would start with a Step wave generator such as the UPS [Un-interruptible power supply] style power supplies used on computers. Tap in to the frequency department of the convertor board, and vary its frequency by means of a separate timing device, or if its not a chip design for the frequency handling, alter what you can to get that range by the use of a pot, or what ever holds the RC function at 50 Hz?<p> If there is a chip and it is propriety and un-alterable, cut it out all together and build a simple stair case generator and feed it back into the rest of the circuit at the same point, to control the FETS that make up the rest of the supply unit. <p>British and Australian units use 240 volts 50 cycles. <p> I forget What India uses as I haven’t been there in a while?
***************
Actually I meant to add in you will need to do other things, like replace the Fets with large ones that can handle the 50 amps. But use the original unit to copy and build a larger version and you can Run this unit off of batteries, or a AC input rectified back to DC, with large caps, and adjusted acording to your design? <p>DC is essential on the IN put so that you can vary the out put with out any affect from a sine wave coming in.<p>[ March 24, 2004: Message edited by: Chris Smith ]</p>
***************
Actually I meant to add in you will need to do other things, like replace the Fets with large ones that can handle the 50 amps. But use the original unit to copy and build a larger version and you can Run this unit off of batteries, or a AC input rectified back to DC, with large caps, and adjusted acording to your design? <p>DC is essential on the IN put so that you can vary the out put with out any affect from a sine wave coming in.<p>[ March 24, 2004: Message edited by: Chris Smith ]</p>
Re: Varying AC frequency
Thanks Chris,
In INDIA we use 220-250V 50Hz AC. In fact what you have mentioned, I am also looking on the same line but I am not much aware about functioning of UPS or Power Inverters. Because of this I have recently posted new thread seeking help and info on working of these UPS and inverter stuffs. <p>Are you aware of any good source of technical info on UPS/Inverters?<p>Thanks,
Sunil
In INDIA we use 220-250V 50Hz AC. In fact what you have mentioned, I am also looking on the same line but I am not much aware about functioning of UPS or Power Inverters. Because of this I have recently posted new thread seeking help and info on working of these UPS and inverter stuffs. <p>Are you aware of any good source of technical info on UPS/Inverters?<p>Thanks,
Sunil
Re: Varying AC frequency
Sunhil,
If you're looking to control a motor, Pulse Width Modulation circuitry through Hi-power Triacs or SCR's.
If you're modulating actual power ( for whatever reason) you have to consider effects on the power utility's grid.
For data, search "carrier current" systems. They use a transformer to AM modulate your wall outlet with a few kHz, to send data/music locally. But not far.
For true FM modulation, the circuits almost exclusively have a DC voltage source, with a fixed frequency oscillator being pushed (modulated) OFF that center frequency.
So, you'd have to RECTIFY 240V,40A,50Hz to DC, feed a mammoth oscillator, and then modulate.
I would look more at phase modulation, if it's data. Either harmonics of the 50Hz (150Hz & 200Hz) sent as pulses, or an H.I.D. lamp ballast (which has capacitors and an inductor) with a carbon-pile resistor (battery tester) as an RLC network to phase-shift a component onto the 50Hz. In either case, the phase / pulse mod. signal could be a few % of line current, and still be detected. Of course, your BAUD RATE will be 25-50 Hz at best.
If you're looking to control a motor, Pulse Width Modulation circuitry through Hi-power Triacs or SCR's.
If you're modulating actual power ( for whatever reason) you have to consider effects on the power utility's grid.
For data, search "carrier current" systems. They use a transformer to AM modulate your wall outlet with a few kHz, to send data/music locally. But not far.
For true FM modulation, the circuits almost exclusively have a DC voltage source, with a fixed frequency oscillator being pushed (modulated) OFF that center frequency.
So, you'd have to RECTIFY 240V,40A,50Hz to DC, feed a mammoth oscillator, and then modulate.
I would look more at phase modulation, if it's data. Either harmonics of the 50Hz (150Hz & 200Hz) sent as pulses, or an H.I.D. lamp ballast (which has capacitors and an inductor) with a carbon-pile resistor (battery tester) as an RLC network to phase-shift a component onto the 50Hz. In either case, the phase / pulse mod. signal could be a few % of line current, and still be detected. Of course, your BAUD RATE will be 25-50 Hz at best.
Can't we end all posts with a comical quip?
Re: Varying AC frequency
My first thought is possibly to first rectify AC to DC then use a multiple mosfets in parallel. A variable signal unit controls the gates. The transistors mounted on a square tube that water circulates thru. The modulation might use the number of mosfets at any given moment but I am not sure what else would be necessary it seems like some kind of massive current control would be tied in.
In which case the triacs phase properties suggested would be useful.<p>Another approach might be to have a small fm modulator/exiter followed by a large linear..<p>[ March 25, 2004: Message edited by: dimbulb ]</p>
In which case the triacs phase properties suggested would be useful.<p>Another approach might be to have a small fm modulator/exiter followed by a large linear..<p>[ March 25, 2004: Message edited by: dimbulb ]</p>
- Chris Smith
- Posts: 4325
- Joined: Tue Dec 04, 2001 1:01 am
- Location: Bieber Ca.
Re: Varying AC frequency
I would contact some of the manufactures them self. I did some extensive research back about 5 or more years on the step wave and UPS design and I recall the manufactures of these devices had quite a bit of information and diagrams on the subject. <p>Most are made in china these days, but you should be able to look up brands like “trip lite” and a few other US companies?<p> I even saw at the time a few Chinese web sites with full diagrams of their products. <p>The only data sheet I had many years back was on the Stair case generator it self, but Im not sure I still have that one in my data base?<p> It would show you the principal [only] behind the ramping of the signal. I ll look to see If I still have it?
Who is online
Users browsing this forum: Ahrefs [Bot] and 19 guests