On Jul 11, 1:43*am, K7ITM wrote:
On Jul 10, 6:09 pm, raypsi wrote:





I searched but couldn't find anything on:

Using 2 transformers
*running the primary of one right off the mains
running the other transformer primary in series
*with a large motor run capacitor to phase shift
the primary 90 degrees.
Rectify and filter both secondaries
Diode "OR" the rectified filtered outputs.
This would give me better than double the frequency
As the phase shift would overlap the
120 cycle pulsating DC.

Basicly I have 2 Eico 751 power supplies.
I like to beef up the supply to my Eico 753.

73
N8ZU

Suggest you run a simulation of your circuit in something like
LTSpice. *It probably does not behave like you are thinking it will.
Transformers are wound with enough inductance that they look like a
moderately high impedance in parallel with the reflected secondary
load. *But if the secondary is loaded with a full-wave or bridge
rectifier into a big capacitance, then current flows only when the
secondary voltage is greater than the capacitor voltage (by a diode
drop or two). *So you end up drawing very little current on the
primary side, except when the voltage is near the peak. *As a result,
you don't get a nice phase-shifted sine on the primary side.

Even if the load looks resistive, the current in the load is not 90
degrees out of phase with the mains voltage; it's just 90 degrees out
of phase with whatever voltage drops across the capacitor.

Try some simulations with various loads and series capacitor values,
and you'll get a feel for what's going on. *If you want, I could send
you the simulation file I just hacked together as a starting point.

Cheers,
Tom- Hide quoted text -

- Show quoted text -


Thanks Tom,

Looks like I been just chasing my tail.

I'll have to go with a 3 phase rotory converter.
That's like a 3hp 3 phase motor with phase shift
capacitor plus a run capacitor,
to run a 3 phase 3hp motor from a
single phase.
I then pull 2 phases off the motor
to run my supplys
. They use 3 phase rotory converters
to deliver 3 phase power to equipment that has to
have 3 phase power to run properly.
I seen one running on youtube.

On Sun, 13 Jul 2008 03:18:42 -0700 (PDT), raypsi
wrote:

On Jul 11, 1:43*am, K7ITM wrote:
On Jul 10, 6:09 pm, raypsi wrote:





I searched but couldn't find anything on:

Using 2 transformers
*running the primary of one right off the mains
running the other transformer primary in series
*with a large motor run capacitor to phase shift
the primary 90 degrees.
Rectify and filter both secondaries
Diode "OR" the rectified filtered outputs.
This would give me better than double the frequency
As the phase shift would overlap the
120 cycle pulsating DC.

Basicly I have 2 Eico 751 power supplies.
I like to beef up the supply to my Eico 753.

73
N8ZU

Suggest you run a simulation of your circuit in something like
LTSpice. *It probably does not behave like you are thinking it will.
Transformers are wound with enough inductance that they look like a
moderately high impedance in parallel with the reflected secondary
load. *But if the secondary is loaded with a full-wave or bridge
rectifier into a big capacitance, then current flows only when the
secondary voltage is greater than the capacitor voltage (by a diode
drop or two). *So you end up drawing very little current on the
primary side, except when the voltage is near the peak. *As a result,
you don't get a nice phase-shifted sine on the primary side.

Even if the load looks resistive, the current in the load is not 90
degrees out of phase with the mains voltage; it's just 90 degrees out
of phase with whatever voltage drops across the capacitor.

Try some simulations with various loads and series capacitor values,
and you'll get a feel for what's going on. *If you want, I could send
you the simulation file I just hacked together as a starting point.

Cheers,
Tom- Hide quoted text -

- Show quoted text -


Thanks Tom,

Looks like I been just chasing my tail.

I'll have to go with a 3 phase rotory converter.
That's like a 3hp 3 phase motor with phase shift
capacitor plus a run capacitor,
to run a 3 phase 3hp motor from a
single phase.
I then pull 2 phases off the motor
to run my supplys
. They use 3 phase rotory converters
to deliver 3 phase power to equipment that has to
have 3 phase power to run properly.
I seen one running on youtube.

Rotary converters in 2008 ????

There are quite a few solid state converters for driving 3 phase
bidirectional motors even from as single phase supply at such low
power levels.

If the original requirement was to generate sufficient power into a
tube transmitter anode supply, I would look into a switching power
supply.

There are of course problems finding high voltage rectifiers for
higher frequencies than 50/60 Hz and the RF noise might be an issue,
but if you can kill the power supply during receive, the RF noise
should not be an issue.

Paul OH3LWR