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Registered Member #135
Joined: Sat Feb 11 2006, 12:06AM
Location: Anywhere is fine
Posts: 1735
Hi Bob,
This is a 300V (can go to 450V if you're not careful) SMPS I'm designing for a friend of mine. Runs off of 9-15V, 86% efficiency at the moment, should be higher soon, and it is VERY HEAVY for 20W.
Many people have tried, but the major problem is the power source, ultimately a battery, is very heavy.
and trying to get 50-75KV out of a compact SMPS is a challenge.
Instead of trying to make the supply smaller, you are going to have to make the lifter surface area larger.
If you do the calculations for the energy required (I have not), I would bet you a can of coke that to get 15 min. run time of a self-contained lifer, that is battery and SMPS, the power source would probably weigh no less than 10 lbs, and the lifter would be nearly the size of a Football field.
I'm not trying to be mean or anything, just realistic.
Registered Member #55219
Joined: Tue Jun 09 2015, 11:21PM
Location:
Posts: 80
how bout a small flyback (lopt) xfmr such as those used in plasma globes and those from small crt tv's (5" or less) / 1980's cam-corder eyepieces? drive it with a SMT mazzilli zvs driver (logic lvl mfets) from a single 18650 lipo (high discharge rated)... Smallest thing I can think of... and still going to be heavy for the ionocraft
Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140
I thik that 10 lbs. is very pessimistic,
since batteries seem to be around 0.2 g/W the most obvious solution seems to be many many small LiPo cells in series impossible to get more W/g
do not ask me how to switch it on/off without electrocution
P.S. regarding stability: the lower vanes can be simply operated by a central pendulum connected by a thin metal rod. one pendulum can control multiple surfaces.
Registered Member #58454
Joined: Thu Feb 18 2016, 06:33AM
Location:
Posts: 23
jdub1581hv wrote ...
how bout a small flyback (lopt) xfmr such as those used in plasma globes and those from small crt tv's (5" or less) / 1980's cam-corder eyepieces? drive it with a SMT mazzilli zvs driver (logic lvl mfets) from a single 18650 lipo (high discharge rated)... Smallest thing I can think of... and still going to be heavy for the ionocraft
I looked at small transformers available for purchase and they had worse than 1 to 3 power(watts) to weight(grams) ratios. I would think if these commercial products such as plasma globes had very light for their power transformers then such would be available for purchase, but I haven't seen any. Remember it's not just they be light weight, but also high power for that light weight.
See for example the small sized high voltage converters here:
In the example of the plasma globe it's likely the transformers are small but the power requirements are smaller.
Registered Member #58454
Joined: Thu Feb 18 2016, 06:33AM
Location:
Posts: 23
Hazmatt_(The Underdog) wrote ...
Hi Bob,
This is a 300V (can go to 450V if you're not careful) SMPS I'm designing for a friend of mine. Runs off of 9-15V, 86% efficiency at the moment, should be higher soon, and it is VERY HEAVY for 20W. Many people have tried, but the major problem is the power source, ultimately a battery, is very heavy. and trying to get 50-75KV out of a compact SMPS is a challenge. Instead of trying to make the supply smaller, you are going to have to make the lifter surface area larger. If you do the calculations for the energy required (I have not), I would bet you a can of coke that to get 15 min. run time of a self-contained lifer, that is battery and SMPS, the power source would probably weigh no less than 10 lbs, and the lifter would be nearly the size of a Football field. I'm not trying to be mean or anything, just realistic.
The weight of the batteries is not really the problem. Batteries of high power for the weight already exist because they are needed for small electric powered airplanes and drones. See for example the batteries here:
They already get multiple times better than 1 watt power per gram of battery weight.
Many amateurs have built tesla coils (air core transformers). What are some of the power to weight ratios for those?
But how lightweight can an air cored transformer be? Less than 1 gram weight per watt power output would be ideal.
From a formal point of view, there is no weight/power ratio for air cored transformers. Imagine a transformer loaded by some resistance with an input voltage of say 10 V. There will be some current in the windings causing losses due to the copper resistance. Now apply a 100V. Then currents will be multiplied by 10. Input power will be multiplied by 100. Losses will also be multiplied by 100. So the loss to power input ratio i.e. the efficiency will stay the same. Your transformer might go up in smoke, but that is a cooling issue not one of efficiency.
You will want, of course, the transformer to be efficient, aside from the power it can handle. That's an interesting question by itself, so I went through the math initially neglecting skin effects. The result is surprising. For a toroidal shape, the power loss fraction depends solely on the mass of copper m, frequency f and the size of the toroid s. The result is:
Ploss/Pinput = 20000 kg * s / (m * f), s in m and f in Hz.
So for a 5cm toroid and a frequency of 50kHz, the power loss would be about 10% for 200 g of copper. That is quite a bit and since I neglected skin effects, the efficiency could be significantly worse. A large frequency increases efficiency only up to a certain point, since the skin effect will limit efficiency gains.
I believe you will be better off with a ferrite core. That will reduce the amount of copper needed so that its weight becomes insignificant compared to the weight of the core. There are cores in the 10s of grams range, which can handle a kW of power at say a 100kHz. It probably makes sense to add a Greinacher multiplier stage behind the transformer in order to alleviate insulation issues.
Registered Member #58454
Joined: Thu Feb 18 2016, 06:33AM
Location:
Posts: 23
Uspring wrote ...
Robert Clark wrote:
But how lightweight can an air cored transformer be? Less than 1 gram weight per watt power output would be ideal.
From a formal point of view, there is no weight/power ratio for air cored transformers. Imagine a transformer loaded by some resistance with an input voltage of say 10 V. There will be some current in the windings causing losses due to the copper resistance. Now apply a 100V. Then currents will be multiplied by 10. Input power will be multiplied by 100. Losses will also be multiplied by 100. So the loss to power input ratio i.e. the efficiency will stay the same. Your transformer might go up in smoke, but that is a cooling issue not one of efficiency. You will want, of course, the transformer to be efficient, aside from the power it can handle. That's an interesting question by itself, so I went through the math initially neglecting skin effects. The result is surprising. For a toroidal shape, the power loss fraction depends solely on the mass of copper m, frequency f and the size of the toroid s. The result is: Ploss/Pinput = 20000 kg * s / (m * f), s in m and f in Hz. So for a 5cm toroid and a frequency of 50kHz, the power loss would be about 10% for 200 g of copper. That is quite a bit and since I neglected skin effects, the efficiency could be significantly worse. A large frequency increases efficiency only up to a certain point, since the skin effect will limit efficiency gains. I believe you will be better off with a ferrite core. That will reduce the amount of copper needed so that its weight becomes insignificant compared to the weight of the core. There are cores in the 10s of grams range, which can handle a kW of power at say a 100kHz. It probably makes sense to add a Greinacher multiplier stage behind the transformer in order to alleviate insulation issues.
Thanks for the informative response. Perhaps switching to aluminum wires would save on the weight of the wiring? Aluminum weighs 1/3rd as much as copper.
About iron or ferrite core transformers the best I could find in power to weight ratio were in the range of 1 watts per 3 grams. But the lifters can only manage about 1 gram-force thrust per 1 watt of power input. So we would need to improve the power to weight ratio of the transformers by better than 3 times for this to work.
A transformer you mentioned at only 10's of grams weight able to handle a kW of power would work if it can go into say the thousand volt output range. Do you have a link for it?
Registered Member #58454
Joined: Thu Feb 18 2016, 06:33AM
Location:
Posts: 23
Thanks for that. I looked at the link, and while it did give equations for calculating the wattage of a transformer, it didn't give any weights. The 1 watt per gram goal is a severe constraint.
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Lightweight air core transformer?
