Convert electrical frequency and change square to sin wave
Convert electrical frequency and change square to sin wave
(OP)
I am a plasma physics innovator. I just completed the design of a power generator using plasma-MHD. The system outputs square waves at approximately 3000 Hz with powers output between 2.5 MW (500 Hz) to 20 MW (3 kHz). Does anybody know how I can convert this to useable utility power frequency (50/60 Hz)? I can do this by slowing down the system, but I am loosing too much power. Also, I am extracting power through multi pin electrodes at maximum 60 Amps per pin, so each pin can create its own circuit (at high frequency the pin current is under 1 amp). Is there a simple method to digitally change the shape from the square wave output to a sin wave to match the shape and frequency of the local utility power lines?






RE: Convert electrical frequency and change square to sin wave
RE: Convert electrical frequency and change square to sin wave
Yes, rectify to DC then invert.
At 20MW you are at utility levels. Find the companies that convert DC to 3phase AC for power transmission. Your application should be easy.
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: Convert electrical frequency and change square to sin wave
Cycloconverters were used to drive very large variable speed low speed motors many years ago. They are more-or-less extinct since the advent of PWM drives (and all their subsets).
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Sometimes I only open my mouth to swap feet...
RE: Convert electrical frequency and change square to sin wave
Another method for atheeanne would be to drive a motor and use this to turn a generator. I think maybe all other methods would require the use of harmonic filters.
RE: Convert electrical frequency and change square to sin wave
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: Convert electrical frequency and change square to sin wave
A star for you. I don't normally tend to think of 20MW systems as single phase. Oops! I haven't seen a single phase cycloconverter - I'm not sure that such an animal even exists.
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Sometimes I only open my mouth to swap feet...
RE: Convert electrical frequency and change square to sin wave
RE: Convert electrical frequency and change square to sin wave
RE: Convert electrical frequency and change square to sin wave
I'm in the rectifier camp on this one. Too many other problems trying to convert something at that high of a frequency.
JRaef.com
Eng-Tips: Help for your job, not for your homework Read FAQ731-376
RE: Convert electrical frequency and change square to sin wave
Each pin constitutes an independent circuit, so even though we are speaking at overall utility power levels we need to change the shape of the pulse at much lower levels per each circuit of each pin. I guess, this will be easier to deal with. The generation and reenergizing of plasma in the plasma reactor is in the order of microseconds, so it is conceivable that higher frequencies are possible to nearly continuous wave (DC), but it would create more problems with cooling. For aerospace and ionic levitation, a new field in aerospace and space propulsion, the power generator is fine, since high voltages (40kV in average) and low current levels can be brnached from each pin. One pound of weight has been lifted (levitated) with 716 watts trough air ionization (demonstrated in 1964).
In order to have the plasma-MHD generator useable for power distribution (utility), however, we need a good sine wave at an acceptable frequency. Each pin circuit can be treated independently and than connected together to the grid. I need help from here; any comments?
RE: Convert electrical frequency and change square to sin wave
There is a wave which bounces from one end of the tube to the other.
The wave makes an output of 60A flow on each pin, but not at the same time, since the wave is travelling across the pins.
So you cannot simply add all the currents on all the pins to get 6000A.
Maybe I misunderstood?
itsmoked, a square wave to a motor: yes, but a great deal of harmonic heating (and noise). It could be rectified and applied to a dc machine, but then isn't the voltage applied to the individual windings of a dc machine similar to a square wave? It seems to be a dc voltage switched by the commutator.
RE: Convert electrical frequency and change square to sin wave
The rectifier method seems to make the most sense since it would allow complete flexibility of the MHD generator allowing throttling etc that would be very limited with any other methods so far mentioned.
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: Convert electrical frequency and change square to sin wave
Good point, however, think of this: in my previous example 100 pins are set along a 10 inch plasma tube. The plasma is oscillating back and forth at 6 kHz. This means that a full square wave (positive and negative) is obtained at 3 kHz (a period of 333 microseconds); 167 microseconds for half of square wave. Since the pins are set up along the 10 inch plasma tube the current seen and extracted by each pin will be some 1.67 microseconds apart; 100 pins (the length of the tube and the plasma traveling in one direction) will extract 60 amps per each pin (not at the same time of course but very close together in the same direction of plasma travel) that yields a total of 6,000 amps along the tube 1.67 microseconds exposure per pin per half wave (60 amps X 100 pins). In reality, with the plasma moving back and forth exposed to a perpendicular magnetic field, one will see a square wave on the positive (above the axis) side 167 microseconds long (in one direction) and on the negative side (in the other direction). So one square wave above and below the line will have a total period of 333 microseconds, each formed by 100 segments above the axis and 100 segments bellow the axis 1.67 microseconds apart. With an output power of a generator capable of producing 14.5 MW, and the output extracted voltage of 7,200 Volts, the total current extracted should be about 2,000 amps (in one direction of plasma tube travel) or 20 amps per pin (1.67 microseconds apart) and 2,000 amps on the return of the plasma putting the wave below the axis, also at 2,000 amps per length of the plasma tube or 20 amps per pin 1.67 microseconds apart.. Are there any comments? I am not an expert, so I hope you can help me find a way to go to 50-60 Hz frequencies sin waves.
RE: Convert electrical frequency and change square to sin wave
RE: Convert electrical frequency and change square to sin wave
From memory, TMEIC is using a development of the transistor base (old = IGBT, new =IEGT), and Siemens is using a development of the thyristor base.
http
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htt
IEGT:
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IGBT:
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TMEIC TM-70 specification and application guide (up to 30MW at 3.3kV):
http://www
That's all for now.
RE: Convert electrical frequency and change square to sin wave
Or will each pin generate only a short pulse while the plasma moves past, say a constant 20 amps for 1.67 microseconds, then no current until the plasma comes back the other direction? In this case, if you connect all the pins together, you will collect 100 pulses of current that are 1.67 microseconds apart, and you will get a 20 amp square wave at 3 kHz, not a 2000 amp square wave.
RE: Convert electrical frequency and change square to sin wave
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: Convert electrical frequency and change square to sin wave
Dave, thank you for your advise, I will look into the specified links for the TMEIC from Siemens.
RE: Convert electrical frequency and change square to sin wave