230VAC/50Hz -> 115VAC/60Hz converter

S

Squidster

Guest
Hello,
I'm trying to design a 230VAC/50Hz to 115VAC/60Hz converter. This is
specifically for applications that are frequency sensitive.

Specs:
Input: 220-240VAC/50Hz (plusminus 1Hz) @10A
Output1: 110-120VAC/50Hz (plusminus 1Hz) @20A \Combined is 20A
Output2: 110-120VAC/60Hz (plusminus 1Hz) @20A /

Here's the blocks:
1. 230VAC/50Hz input, offline rectified and filtered to 340VDC.
2. Chopped up (20-50Khz) either via a BJT or MOSFET power switch with PWM
controller (either 555 or PWM IC).
3. PWM wave fed into a high-frequency transformer (2:1)
4. Rectified secondary with schottky power diodes to recover DC.
5. This then is pass throught the 2nd. stage low-frequency choppers one
for 50Hz and one for 60Hz.
6. After going through the 50Hz and 60Hz choppers; we pass through a final
stage of low-pass-filter (LC, with fT=50 and fT=60 respectively)
7. Feedback from output fedback into the PWM controller.

Is there anything fundamentally wrong with the design?
I went through 2 stages because I wanted to avoid a huge mains transformer
rated at 20A!

Comments, caveats, experiences, component choices, are welcome!
I need some further design help on the:
- high-frequency 2:1 transformer
- PWM controller (IC recommendations?)
- chopper drive

Thanks!
/wai-sun
 
In sci.electronics.design Squidster <squidster3128@yahoo.com> wrote:
Hello,
I'm trying to design a 230VAC/50Hz to 115VAC/60Hz converter. This is
specifically for applications that are frequency sensitive.

Specs:
Input: 220-240VAC/50Hz (plusminus 1Hz) @10A
Output1: 110-120VAC/50Hz (plusminus 1Hz) @20A \Combined is 20A
Output2: 110-120VAC/60Hz (plusminus 1Hz) @20A /
Click to expand...
Must output be galvanicly isolated or something?

Here's the blocks:
1. 230VAC/50Hz input, offline rectified and filtered to 340VDC.
filter = capacitors?
Click to expand...

Extra capacitor network with a semiconductor in parallel with mains to
perform active powerfactor correction?
(needs feedback too ;)

2. Chopped up (20-50Khz) either via a BJT or MOSFET power switch with PWM
controller (either 555 or PWM IC).
3. PWM wave fed into a high-frequency transformer (2:1)

4. Rectified secondary with schottky power diodes to recover DC.
5. This then is pass throught the 2nd. stage low-frequency choppers one
for 50Hz and one for 60Hz.
6. After going through the 50Hz and 60Hz choppers; we pass through a final
stage of low-pass-filter (LC, with fT=50 and fT=60 respectively)
7. Feedback from output fedback into the PWM controller.

Is there anything fundamentally wrong with the design?
I went through 2 stages because I wanted to avoid a huge mains transformer
rated at 20A!

Comments, caveats, experiences, component choices, are welcome!
I need some further design help on the:
- high-frequency 2:1 transformer
pulvercore?
Click to expand...

- PWM controller (IC recommendations?)
- chopper drive
Click to expand...
Maybe IBGT will do the job?
You could even do sinewave pwm and have sine output..
 
"Squidster" <squidster3128@yahoo.com> schreef in bericht
news:pan.2004.10.13.08.26.05.920713@yahoo.com...
Hello,
I'm trying to design a 230VAC/50Hz to 115VAC/60Hz converter. This is
specifically for applications that are frequency sensitive.

Specs:
Input: 220-240VAC/50Hz (plusminus 1Hz) @10A
Output1: 110-120VAC/50Hz (plusminus 1Hz) @20A \Combined is 20A
Output2: 110-120VAC/60Hz (plusminus 1Hz) @20A /
Click to expand...
[snip]

Is there anything fundamentally wrong with the design?
I went through 2 stages because I wanted to avoid a huge mains transformer
rated at 20A!
Click to expand...
I don't know, but there is at least something fundamentally wrong
with the specs. 100% efficiency is impossible. Two stages at 80%
gives 65%.

--
Thanks, Frank.
(remove 'x' and 'invalid' when replying by email)
 
Squidster wrote:

4. Rectified secondary with schottky power diodes to recover DC.


Comments, caveats, experiences, component choices, are welcome!
Click to expand...
Specifically, Shottky diodes are normally only suitable for low voltage.

Those filters are going to be damn large too. Might be better to generate the
50 & 60 Hz using ( say 30kHz ) PWM rather than chopping.


Graham
 
Pooh Bear wrote:

--snip--

Specifically, Shottky diodes are normally only suitable for low voltage.
-- snip--
Graham
Click to expand...
http://www.cree.com/ftp/pub/CSD20060.pdf

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
 
On Wed, 13 Oct 2004 15:58:45 -0700, the renowned Tim Wescott
<tim@wescottnospamdesign.com> wrote:

Pooh Bear wrote:

--snip--

Specifically, Shottky diodes are normally only suitable for low voltage.
-- snip--
Graham


http://www.cree.com/ftp/pub/CSD20060.pdf
Click to expand...
Hmm... I wonder if they think it's a liability to mention that it's a
Silicon Carbide device?


Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
 
Spehro Pefhany wrote:

On Wed, 13 Oct 2004 15:58:45 -0700, the renowned Tim Wescott
tim@wescottnospamdesign.com> wrote:


Pooh Bear wrote:

--snip--


Specifically, Shottky diodes are normally only suitable for low voltage.

-- snip--

Graham


http://www.cree.com/ftp/pub/CSD20060.pdf


Hmm... I wonder if they think it's a liability to mention that it's a
Silicon Carbide device?


Best regards,
Spehro Pefhany
Click to expand...
Good question -- I don't do any design at 600V, but I question how much
better a SiC shottkey with a 1.5V forward drop is over a silicon diode.
I suppose the recovery time can't be beat...

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
 
Tim Wescott wrote:

Pooh Bear wrote:

--snip--

Specifically, Shottky diodes are normally only suitable for low voltage.
-- snip--
Graham


http://www.cree.com/ftp/pub/CSD20060.pdf
Click to expand...
Sadly the forward voltage makes it rather less helpful in this application
than 'normal' schottkies.


Graham
 
Pooh Bear wrote:

Tim Wescott wrote:


Pooh Bear wrote:

--snip--


Specifically, Shottky diodes are normally only suitable for low voltage.

-- snip--

Graham


http://www.cree.com/ftp/pub/CSD20060.pdf



Sadly the forward voltage makes it rather less helpful in this application
than 'normal' schottkies.


Graham

Well, I view that page as kind of a party trick -- something to pull out
Click to expand...
of my pocket whenever someone mentions that schottkeys are low voltage.

But it's not a bad forward voltage for something that'll hold off 600V,
and it should have really good reverse recovery characteristics, not to
mention thermal properties.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
 
Rich Grise wrote:

On Wednesday 13 October 2004 01:25 am, Squidster did deign to grace us with
the following:


Hello,
I'm trying to design a 230VAC/50Hz to 115VAC/60Hz converter. This is
specifically for applications that are frequency sensitive.

Specs:
Input: 220-240VAC/50Hz (plusminus 1Hz) @10A
Output1: 110-120VAC/50Hz (plusminus 1Hz) @20A \Combined is 20A
Output2: 110-120VAC/60Hz (plusminus 1Hz) @20A /

Here's the blocks:
1. 230VAC/50Hz input, offline rectified and filtered to 340VDC.
2. Chopped up (20-50Khz) either via a BJT or MOSFET power switch with PWM
controller (either 555 or PWM IC).
3. PWM wave fed into a high-frequency transformer (2:1)
4. Rectified secondary with schottky power diodes to recover DC.
5. This then is pass throught the 2nd. stage low-frequency choppers one
for 50Hz and one for 60Hz.
6. After going through the 50Hz and 60Hz choppers; we pass through a final
stage of low-pass-filter (LC, with fT=50 and fT=60 respectively)
7. Feedback from output fedback into the PWM controller.

Is there anything fundamentally wrong with the design?


Yes.

1. It's obviously homework. We don't do other people's homework for
free.

2. This is a terribly stupid approach to this problem, when you can
get a 50 HZ synchronous motor and couple it to a 115V 60 Hz generator,
for about one-tenth the time and money.

Have Fun!
Rich

1. If it were homework it'd be better framed (see Mr. Bemelman's
Click to expand...
comment about 100% efficiency).

2. I suspect that a solid-state solution would be smaller and cheaper
_if_ you're doing this for production -- but then I suspect that
_someone_ makes these already. The synchronous motor/60Hz generator
idea may work quite well if you can get something surplus.

If I were going to do this I'd also investigate just generating the
120VAC straight off of the 340VDC rail. As pointed out by Gibbo, you're
going to do a _lot_ of work on this -- it'd be a good vehicle for
learning power switching electronics (if you don't kill yourself), but
you should get help if you want to do this for production, or look for
an existing converter if you just need it.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
 
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