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Registered Member #58454
Joined: Thu Feb 18 2016, 06:33AM
Location:
Posts: 23
I wondered if staging the Cockcroft-Walton voltage multiplier can be arranged so that adding stages increases the voltage by factors of 2. As they are used now, the voltage is only increased additively by adding additional stages. That is, adding another stage increases the voltage to 3 times, another to 4 times, another to 5 times, etc. I was seeking an arrangement that would instead multiply the voltage times two with each stage. The response I got was the CW takes AC then sends it to DC. So I would need to then convert the output to AC to apply another CW under this arrangement. But then this would bring it back to the same AC range at the beginning.
So how about this circuit, the Greinacher voltage quadrupler:
I'm looking at the quadrupler discussed there not the doubler. Then even if when adding a DC to AC converter the peak AC voltage got halved, the peak AC out would still be double that of the initial AC in.
So repeating this circuit consisting of a Greinacher quadrupler followed by a DC to AC converter, I would get a voltage doubling at each stage.
Registered Member #11591
Joined: Wed Mar 20 2013, 08:20PM
Location: UK
Posts: 556
Why would you want to do that? The impractical bit is the DC to AC converter (inverters). The CW multiplier is only practical at low currents and high voltages, which means that the AC to DC converter would have to run at exponentially higher voltages and lower currents. Such inverters do not exist, unfortunately.
Registered Member #58454
Joined: Thu Feb 18 2016, 06:33AM
Location:
Posts: 23
hen918 wrote ...
Why would you want to do that? The impractical bit is the DC to AC converter (inverters). The CW multiplier is only practical at low currents and high voltages, which means that the AC to DC converter would have to run at exponentially higher voltages and lower currents. Such inverters do not exist, unfortunately.
I'm investigating the ionocraft, commonly called "lifters":
They require thousands of volts. The high voltage is usually provided by transformers. But transformers are heavy. I need a lightweight means to increase the voltage to that extent. If I just used CW multipliers I would need thousands of stages to get the voltage I need starting from battery voltage. But if I get a circuit that could double the voltage at each stage I would only need ten.
Registered Member #58454
Joined: Thu Feb 18 2016, 06:33AM
Location:
Posts: 23
Erlend^SE wrote ...
I don't quite see the problem: start with a transformer and CW stack up from it.
What are you trying to do?
The best power to weight I've seen for a transformer is 1 watts per 3 grams weight. But the lifters typically manage only about 1 gram weight of thrust produced per watt of power used. So you can't use a transformer. They would have to be made lighter than the ones available now at least by a factor of 3, actually even better than that since that is not including the weight of the lifter itself or the battery. That is why I'm investigating lightweight means of producing the high voltage.
Do a google image search on "lifters", "power supplies", "high voltage". You'll find the lifters are flimsy little devices that weigh no more than a few grams but the power supplies are large and heavy weighing in the range of kilograms.
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
Robert Clark wrote ...
The best power to weight I've seen for a transformer is 1 watts per 3 grams weight. . . .
i build planar HV transformers for my lifter research, and will be starting an entirely new development phase soon.
Ive been able to get much better than 1 watt per 3 grams already, way better. Modern mosfets, ferrite and high frequency have solved a lot of DeSeversky's mass problems. the bigger problem is where to get power. that gets heavy to.
there are five pages here:
The power supplies your looking at arent meant for power density, they're typically meant for industrial, commercial and decades long use for the buyer, that's why your seeing such poor numbers i think.
My website isn't fully up yet, but Ive been doing ionocraft research operation since the mid 90's.
Registered Member #58454
Joined: Thu Feb 18 2016, 06:33AM
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Posts: 23
Patrick wrote ...
Robert Clark wrote ...
The best power to weight I've seen for a transformer is 1 watts per 3 grams weight. . . .
i build planar HV transformers for my lifter research, and will be starting an entirely new development phase soon. Ive been able to get much better than 1 watt per 3 grams already, way better. Modern mosfets, ferrite and high frequency have solved a lot of DeSeversky's mass problems. the bigger problem is where to get power. that gets heavy to.
there are five pages here:
The power supplies your looking at arent meant for power density, they're typically meant for industrial, commercial and decades long use for the buyer, that's why your seeing such poor numbers i think. My website isn't fully up yet, but Ive been doing ionocraft research operation since the mid 90's.
Thanks for the response. There are cases for where it is important to have lightweight power conversion for the consumer and the power density is still poor. For instance I was impressed by the small size of the Apple adapter(charger) for the iPhone. It's a small cube about an inch on a side. Having those adapters lightweight is important for the consumer of course since frequently you have to log around your charger with your phone.
The charger works by using a small transformer to convert 120V AC to 5V DC. But despite the need to be lightweight it still weighs 20 grams for 5 watts of power, a power to weight ratio of 1 to 4. This is for downshifting the voltage, but the transformers I've seen for shifting the voltage upwards, have similar ratios.
I'd like to see a transformer you built yourself or found from a commercial source that got better than a 1 to 1 power(watts) to weight(grams) ratio.
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
how much power do you need, and at how many volts ? and specifically how are you using this lifter ? is it tethered ?
this transformer is specifically meant for my lifter research: these are planar high frequency transformers, specifically meant for high power. Fully engineered and made by me.
I 3D printed a special bobbin after detailed FEA field strength analysis of the cross section.
The red part is wet wound epoxy to create a voidless secondary. there are 100 turns under there. this transformer isnt fully tested but reaches 7.5kv, its meant in its finished form to be 21-25kv, with advanced features, modulation, current limit and secondary side regulation. its far lighter and is scary powerful than any other bare transformer ive seen or made. with the right circuit board this beats whats your asking for.
Scalability favors larger power supplies and disfavors smaller ones like a wall-wart. packing efficiency being one problem of many.
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Can staged voltage multipliers be multipliplicative instead of additive?
