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Voltage Conversion without Harmonics?

Voltage Conversion without Harmonics?

Voltage Conversion without Harmonics?

Is anyone aware of voltage regulation devices on the market which can convert one AC voltage to another AC voltage without intermediate DC storage and without creating harmonics on the output?  

RE: Voltage Conversion without Harmonics?

Check out ferro-resonate transformers. SOLA is one mfg.

RE: Voltage Conversion without Harmonics?

Suggestion: Check for AC-AC Matrix converters or AC-AC cycloconverters.

RE: Voltage Conversion without Harmonics?

The answer here is yes.  This is a technology called Sequential Discharge Rectification (SDR) which has no dc bus.  It can go AC-AC, AC-DC and DC-DC with less than 1% harmonic current current distortion on input or output, no VAR problems and can go, for example, 440V input to 4.16kV output without transformers.  As SDR is some 8-10 times faster than electronic breakers it done not need them.

I introduced the technology to the UK Royal Navy and then the US Navy for 22MW VFDs for electric proplusion (it is now called in NATO 'resonant conversion'.  ALready a US Army Abrahams Main Battle Tank has been coverted from gas turbine to SDR electric drive with a small diesel generator with tremendous increase in range and maintenance periods.

It is the technology of the future.  

RE: Voltage Conversion without Harmonics?

Comment on the previous posting converter:
The Sequential Capacitive Discharge (SCD) converter consists of Input Filtering, Input Thyristors, Resonant Circuit, Output Thyristors, and Output Filtering Sections. It is suitable for permanent magnet motors, induction motors, etc. It is less suitable for a many-phase motor such as 15-phase or so.  The SCD converter needs noticeable number of capacitors and special type of thermally designed inductors. It is efficient, has a low harmonic distortion and is low cost. In addition to the above posted features, it can be used for VAR controls, harmonic compensation, and electronic transformation.
It is patented by Dr. R. Limpaecher and Dr. E. R. Limpaecher under US Patent number 6118678. It needs to be applied a lot to become the proven technology.

RE: Voltage Conversion without Harmonics?


You are spot on.  Rudi did development the SDR technology through work under the star wars programme.

Although it does need SCRs, caps and inductors it is still around 30/35% cost of conventional 6 Pulse PWM drives without the usual input harmonics (35-38% Ithd based on either ac line or dc bus inductance respectively {assuming 5% source impedance} nor output harmonics or dv/dt problems.  

Rolls Royce is trying to develop it for the NATO electric propulsion projects but seemingly cannot yet get it to fly, hence the use of the 15 phase, multi-layer PWM currently being adopted.

It is best suited to large HP drive (above 800HP) or for MV drives up to 13.8kV.

As you also say it has other applications including active harmonic mitigation and electricity transmission (dc to ac conversion) and vice versa (i.e. linking networks of differing voltages and frequencies on the a single grid.

It does need to be applied in many fields but has potential but may be 5-10 years before we see it as a product in the normal sense.

As a new member it is good to see that the 'gossip shop' actually works and quickly.  Nice to know.

That's all from Scotland for now.

RE: Voltage Conversion without Harmonics?

Small encore: The US Patent 6118678 is available on
and is very informative. Also, Reference
1. R. Limpaecher, et. al, "Harmonic Free New Inverter Topology for High Voltage, High Power Applications," Twenty-Fourth International Power Modulator Symposium, Norfolk, VA, 2000. IEEE publication.

RE: Voltage Conversion without Harmonics?

Small encore: There has been other development pertaining to the previous postings and SCD, namely, Supervisor Dr. R. W. G. Bucknall and Student Lt J. E. Voyce RN (Electrical Option) worked on M.Sc. project "Investigation into the Sequential Capacitive Discharge Converter (SCD)" having very similar or idential circuitry as the one addressed in the previous postings. Visit "M.Sc. Marine Engineering Individual Project Abstracts 1998-1999" at
for more info.

RE: Voltage Conversion without Harmonics?


I tried to get the info on www.dephion.com but the website is no go.  Other than the MENG site is there anyway else I look up to see progress in SDR ?  Please advise...

RE: Voltage Conversion without Harmonics?

I'm flashed from SCD converter. Who has knowlege or know some webpages, finding application notes, descriptions and actual results from the SCD converter Ian C. Evans proposed above?

RE: Voltage Conversion without Harmonics?

I am also interested in online references that I may use to familiarize myself with this technology. Please limit suggestions to those that result in actual info instead of a link that a search engine returns but offers no real info or cannot be accessed without membership.

RE: Voltage Conversion without Harmonics?

How would this device compare to a variable autotransformer?

I'm guessing this electronic gizmo had higher cost.  But probably lower size/weight?  More flexible?

In solid state electronics class they told us about a "cyclo conerter".  Is this the same device?

RE: Voltage Conversion without Harmonics?

Suggestions/answers to the previous post marked ///\\\:
How would this device compare to a variable autotransformer?
///There are some features that cannot be compared, e.g.
1. Frequency variation
2. Four quadrant control
3. Tie between input and output
4. Etc.
Physically, the converter will have more attractive physical parameters.\\\
I'm guessing this electronic gizmo had higher cost.
///Presently, the cost is higher, but in the future, who knows?\\\
But probably lower size/weight?///Yes.\\\
More flexible?///Yes.\\\
In solid state electronics class they told us about a "cyclo conerter".  Is this the same device?///Yes, it is a version of cycloconverters with many attractive features:
1. High efficiency, .e.g. up to 99%
2. Flexible converter
3. Low current distortion, e.g. 1%
4. Principle of operation
5. Etc.
See US Patent 6118678 at one of those above download websites.\\\

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