Low frequency HV generator
iJim, Thu Apr 28 2016, 09:17AMHi All,
I've a neon sign transformer (10kV, 50mA) that I use for generating high voltages. I would like to vary the frequency of operation by +/- 10 Hz and the output voltage. Any ideas on the best way to go about this? i can live with some harmonics, but would like the output to at least resemble a sine wave. My first thought is to use an audio amplifier to provide the low voltage variable amplitude/frequency sine wave. This would be fed in to the low voltage winding of a mains transformer which would drive the neon transformer... Seems like a lot of messing around. I guess another option would be to build a switching power supply and use some filters on the output, but I'm hoping for a relatively quick solution that doesn't require designing something new.
Cheers
Jim
Re: Low frequency HV generator
Mads Barnkob, Thu Apr 28 2016, 09:33AM
You could try to drive the transformer with a VFD variable frequency drive, frequency inverter.
You might need 3 NSTs connected in f.ex. Delta to simulate a 3 phase motor.
Mads Barnkob, Thu Apr 28 2016, 09:33AM
You could try to drive the transformer with a VFD variable frequency drive, frequency inverter.
You might need 3 NSTs connected in f.ex. Delta to simulate a 3 phase motor.
Re: Low frequency HV generator
Erlend^SE, Thu Apr 28 2016, 10:42AM
Audio amplifier and signal generator, add transformer between amplifier output and nst as needed.
Erlend^SE, Thu Apr 28 2016, 10:42AM
Audio amplifier and signal generator, add transformer between amplifier output and nst as needed.
Re: Low frequency HV generator
Patrick, Thu Apr 28 2016, 04:28PM
An SMPS wont be quick or easy.
Patrick, Thu Apr 28 2016, 04:28PM
An SMPS wont be quick or easy.
Re: Low frequency HV generator
radiotech, Mon May 09 2016, 05:13AM
I have driven 120 VAC circuits with frequencies other that 60 Hz.
Here is what was used.:
Variac.
Solid State Stereo Audio Amplifier 200 Watt.
Function Generator
Phase splitting transformer ( actually a Type 120 telephone repeating coil.
The function generator delivers voltage on its 600 ohm output to the primary of the repeating coil.
The secondary of the repeating coil can be wired as two windings in series with center tap.
The center tap goes to amplifier ground. The (+) end goes to the left channel in, The (-) end,
to the right channel in. Aux inputs work best. Amplifier set to 'flat' tone controls in center,
all filters off.
The amplifier is now configured in mono differential. Do not let the amplifier clip.
The left speaker + terminal is connected to the contact arm of the Variac.
The right speaker + terminal is connected to common Variac terminal.
The driven variable frequency load is connected between the common Variac terminal
and the line input terminal.
The system is operated as follows: Connect an AC voltmeter across the connected load.
Adjust the Variac, voltage control, and remember, reducing the setting , increases the
voltage output.
What the Variac is doing is acting as a variable auto transformer, matching the output
impedance (essentially a constant voltage source) to your load impedance at 120 VAC.
A 200 Watt amplifier intended to drive an 8 ohm speaker can deliver 40 volts at 5 Amps.
The setup is used in classroom for certain labs.
Maintain situational awareness with this hookup !
And if you are doing neon magic, keep it within the circle.
-
radiotech, Mon May 09 2016, 05:13AM
I have driven 120 VAC circuits with frequencies other that 60 Hz.
Here is what was used.:
Variac.
Solid State Stereo Audio Amplifier 200 Watt.
Function Generator
Phase splitting transformer ( actually a Type 120 telephone repeating coil.
The function generator delivers voltage on its 600 ohm output to the primary of the repeating coil.
The secondary of the repeating coil can be wired as two windings in series with center tap.
The center tap goes to amplifier ground. The (+) end goes to the left channel in, The (-) end,
to the right channel in. Aux inputs work best. Amplifier set to 'flat' tone controls in center,
all filters off.
The amplifier is now configured in mono differential. Do not let the amplifier clip.
The left speaker + terminal is connected to the contact arm of the Variac.
The right speaker + terminal is connected to common Variac terminal.
The driven variable frequency load is connected between the common Variac terminal
and the line input terminal.
The system is operated as follows: Connect an AC voltmeter across the connected load.
Adjust the Variac, voltage control, and remember, reducing the setting , increases the
voltage output.
What the Variac is doing is acting as a variable auto transformer, matching the output
impedance (essentially a constant voltage source) to your load impedance at 120 VAC.
A 200 Watt amplifier intended to drive an 8 ohm speaker can deliver 40 volts at 5 Amps.
The setup is used in classroom for certain labs.
Maintain situational awareness with this hookup !
And if you are doing neon magic, keep it within the circle.
-
Re: Low frequency HV generator
Nik, Sun May 22 2016, 02:03AM
My main PSU/Function generator is just this. You can parallel up channels to get more current, it will happily go down to 1hz and all you have to do is match the impedance to keep the amp happy.
Nik, Sun May 22 2016, 02:03AM
Erlend^SE wrote ...
Audio amplifier and signal generator, add transformer between amplifier output and nst as needed.
Audio amplifier and signal generator, add transformer between amplifier output and nst as needed.
My main PSU/Function generator is just this. You can parallel up channels to get more current, it will happily go down to 1hz and all you have to do is match the impedance to keep the amp happy.
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