Is a voltage doubler economic?

R

ruxton.stanislaw

Senior Member
Location
Arkansas
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Laboratory Engineer
Is it economic to design a voltage doubler to convert 400Y/230 V to 1.5 kV DC or would a traditional transformer and rectifier be more cost effective? Assume 150 kW; 100 A on the DC load.
 
herding_cats

herding_cats

Senior Member
Location
Kansas
Occupation
Mechanical Engineer
Rectification can have drastic effects on power factor. Check on your utility tariff if there is a penalty for low power factor. If you want answers regarding economics, this could be a big part of the deciding factor.

Is this a battery formation thing or? What's the application?
 
herding_cats

herding_cats

Senior Member
Location
Kansas
Occupation
Mechanical Engineer
You are getting into the realm of a cascade multiplier. Yes, it's triple. This is how stun guns are wired. LOL
 
synchro

synchro

Senior Member
Location
Chicago, IL
Occupation
EE
topgone said:
Yep. It would be a voltage tripler! Grabbed from the web:
View attachment 2570657
Click to expand...

That half-wave tripler would draw DC current from the input, which could then saturate whatever transformer is supplying the 400/230VAC . And so a full wave version would need to be used.

A problem with voltage multipliers is that all of the output current is supplied by means of the charging and discharging of capacitors. And so you're going to need big capacitors to supply the required 100A, and they will be undergoing reasonably high stress. I suspect that there will also be relatively large harmonic currents drawn on the supply side of a voltage multiplier.

By using a transformer to boost the voltage followed by a 3-phase rectifier bridge, capacitors would just be needed to filter the ~13% ripple of a 6-pulse rectifier to the extent required.
The L-L voltage from the transformer can be used to drive the rectifier without causing a significant AC common-mode voltage on the DC output by leaving the secondary of the transformer floating, and then grounding one side of the rectifier's DC output. The isolation provided by the transformer allows this, and it should have other benefits as well.

Switching supplies could be used to boost the voltage, using transformers and/or inductors which would be relatively small because the switching frequency is significantly higher than 60 Hz. I'm not sure if there is something commercially available like this that would fit your needs.
 
R

ruxton.stanislaw

Senior Member
Location
Arkansas
Occupation
Laboratory Engineer
electrofelon said:
Probably to provide inverse reactive current for unilateral phase detractors, that would be my guess.
Click to expand...
Thanks guys, for the input. This is the closest guess! It is to run through an inverter for a different grid and it would technically be a voltage tripler, yes. Isolation is not required, because of the transformers on both sides. For the power factor, what can we do; more capacitors on the AC side? Minimal ripple is preferred; I can specify capacitors as large as necessary including a final filtering stage.

I like the idea of the switching supplies; I will look into that more. Thanks!
 
W

winnie

Senior Member
Location
Springfield, MA, USA
Occupation
Electric motor research
Wait, you are actually going to implement an encabulator? I thought those were only jokes!

Seriously, you are going to be joining two non-synchronous AC systems using an inverter, but only at an operating level of 150kW? And you already have transformers on both sides of this link?

It would seem to me that the most economical solution is to provide the necessary voltage change on one or the other of the transformers that you must already have in the system, rather than adding an additional transformer or voltage tripler.

At the power level you are considering, IMHO the design effort to do anything else would be more expensive than the cost of replacing one of the existing transformers with a known design which provides the voltage change.

-Jonathan
 
R

ruxton.stanislaw

Senior Member
Location
Arkansas
Occupation
Laboratory Engineer
winnie said:
Wait, you are actually going to implement an encabulator? I thought those were only jokes!
Click to expand...
I am waiting for the new model to come out. :)

winnie said:
Seriously, you are going to be joining two non-synchronous AC systems using an inverter, but only at an operating level of 150kW? And you already have transformers on both sides of this link?

At the power level you are considering, IMHO the design effort to do anything else would be more expensive than the cost of replacing one of the existing transformers with a known design which provides the voltage change.
Click to expand...
Thank you kindly Jonathan, for your input. It is in segments of a maximum of 150 kW for regulatory reasons, however, will add up to several MW in the end. Approaching this at 150 kW at a time also ensures we are doing everything the best we can in terms of efficiency and reliability of the hardware etc.

The deciding economic factor regarding transformers is that they are supplied by the utility as part of the connection fee/usage commitment, on both sides, provided that we use the standard commercial voltage here (400Y/230 V 50 Hz). In this case, for any non-standard voltage, we would need to either pay for or supply the transformer ourselves.
 
W

winnie

Senior Member
Location
Springfield, MA, USA
Occupation
Electric motor research
@electrofelon made an Encabulator reference in post #11; OP joked in post #14 that it was close to what they are actually doing. I batted back with a joke question in post #15.

However it seems that the OP has a real project involving power transfer between two different voltage non-synchronized systems.

-Jonathan
 
junkhound

junkhound

Senior Member
Location
Renton, WA
Occupation
EE, power electronics specialty
My LOL was for practicality at 150 kW, did not run a design but think one would need cubic YARDs of capacitor sizes.
 
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