Variable Voltage and Variable Frequency inverter circuit 3

[Wellyee]

Hi all,
I am looking for an inexpensive way of producing 3 phase pure sine wave, variable voltage (0-220Vp-p) and variable frequency (40-100Hz)independent to each other, from a single phase supply. My thought was to use an off-the-shelf pure sine wave AC/AC UPS and modify the IGBT drive circuitry to enable independent control of output voltage and frequency. Can anyone expert in the programming of such drive circuits point me towards the better end of IGBT controllers as I require good stability and fine control in producing a high quality PURE sine wave supply capable of delivering up to 4Amps/phase.
Other ideas are most welcome however I am weight restricted to less than 25kg.

 

[itsmoked]

You say three phase from single phase.

A VFD can do that.


Then you say 0-220V output.

A VFD can sort of do that. It's the zero end that will not be too good.


Then you say 40-100Hz.

A VFD can do that.


The a pure sine wave.

A VFD cannot do that. But adding a filter and perhaps a transformer to the VFD's output can do that.


You say 4Amps/Phase.

A VFD can do that.


You say 25kg.

Maybe you can do that. If the transformer is needed it will be close.


Then you say "control the frequency and voltage of the phases independently".

A VFD cannot do that in any way, shape, or form. Is that really necessary? I'm having trouble even rationalizing a need for that.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[sibeen]

Then you say "control the frequency and voltage of the phases independently".

Keith, I must admit that I didn't read the OP in that way. I'm assuming that he wants to be able to adjust the voltage and have the frequency stay stable or the converse, adjust the frequency whilst having the voltage remain stable.

 

[Skogsgurra]

For test purposes, I think.

Done that with the NFO Sinus drive. Modified the voltage control loop and got a simple synthesised three-phase source with 2.2 kW at maximum 230 V.

It takes some work to make it do what you want, but it is doable. I used a micro processor with three 12 bit DA:s to control the output voltages. Used it to test power circuitry with unbalanced and distorted three-phase voltages. Much, much cheaper than buying or even hiring a three-phase arbitrary generator with close to 10 A output.

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[Wellyee]

Thanks guys,
I do need to vary the voltage whilst maintaining a presettable Frequency. I've noted that VSDs control both voltage and frequency in a preprogrammed manner. I would be happy to use a VSD but again I need to have access to the driver circuit so as to remove that preprogram and reprogram a set (adjustable) frequency then use as a power supply with adjustable output voltage.

 

[Wellyee]

Thanks Skogsgurra,
I've had a quick search for the NFO Sinus Drive and note in their literature "NFO Sinus sets a new global standard with pure sinusoidal output voltage & current", which is definitely a requirement for my intended Test gear. Can you expand on how and where your got access to connect your D/As.
many thanks
Noel

 

[Skogsgurra]

I can send you photos. My address is available on the web.

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[jraef]

Actually you can adjust voltage independently of frequency (a better way of wording it) with most VFDs, if not directly then indirectly by virtue of the functions that allow programming your own V/Hz ratio. Tying that to external analog inputs may be problematic, but if it is available in programming and the VFD has serial communications, you could easily set up a micro-PLC to give you access to that function with external signals.

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