Anyone know where i can find a transformer to convert 240v AC 50hz to roughly 400V AC, 10-50W / High Voltage / Forums

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Anyone know where i can find a transformer to convert 240v AC 50hz to roughly 400V AC, 10-50W

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LAN_403

HV Enthusiast

Sun Apr 21 2013, 02:30PM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
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Posts: 3068

Just find a standard CONTROL TRANSFORMER which are used for industrial applications / panels.

They usually have a 440/480VAC primary and 240/120VAC secondaries, but can be run in reverse.

jpoopdog

Mon Apr 22 2013, 10:54AM

Registered Member #6188 Joined: Wed Aug 15 2012, 08:34AM
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Posts: 23

see if its going to be portable i cant be using big kilowatt transformers . it needs to fit in the palm of my hand
those ones are always huge monster transformers, its really all i ever find, and they are all wrong. ANyway, problem is solved now, i can just use a voltage doubler apparently, i wasnt aware they work so efficiently, or rather that they can output as much power as they do. All i need to do now is something to stop short circuit detection

Ash Small

Mon Apr 22 2013, 11:35AM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

jpoopdog wrote ...

All i need to do now is something to stop short circuit detection

Add a resistor?

jpoopdog

Mon Apr 22 2013, 10:11PM

Registered Member #6188 Joined: Wed Aug 15 2012, 08:34AM
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Posts: 23

that might not be practical since its 75W coursing through, potentially. since the capacitors initially dont offer any resistance at all to begin with

HV Enthusiast

Mon Apr 22 2013, 10:46PM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
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Posts: 3068

A 75VA (75W) transformer is not very big. It will fit in the size of your hand.

jpoopdog

Thu May 02 2013, 08:26AM

Registered Member #6188 Joined: Wed Aug 15 2012, 08:34AM
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Posts: 23

well, i finally got the inverter in the mail, time to test its ability to charge a capacitor.

in theory off the 240v i should be able to charge a capacitor that is rated at 330v. however, what will happen once its full?

klugesmith

Thu May 02 2013, 11:38PM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716

jpoopdog wrote ...

well, i finally got the inverter in the mail, time to test its ability to charge a capacitor.
in theory off the 240v i should be able to charge a capacitor that is rated at 330v. however, what will happen once its full?

Not so fast, poopmeister.
Start by measuring your inverter's AC output voltage, with and without loads.
Light bulbs of various wattage would make good loads.
Try varying the DC input voltage too, if possible.

Then measure your inverter's peak output voltage.
You can do that by using a single diode to charge a small-value capacitor, whose voltage rating is generously high.

If the peak voltage is higher than you want to put on a capacitor that's rated for 330 V,
figure out how fast the capacitor ought to charge up.
It won't hurt to put a power resistor (or light bulb) between the inverter and the capacitor.

If you plan to discharge the capacitor suddenly through a coil, while the charger remains connected,
consider the possibility of damage to your charging rectifier and/or to the inverter.

jpoopdog

Mon May 06 2013, 11:12AM

Registered Member #6188 Joined: Wed Aug 15 2012, 08:34AM
Location:
Posts: 23

klugesmith wrote ...

If you plan to discharge the capacitor suddenly through a coil, while the charger remains connected,
consider the possibility of damage to your charging rectifier and/or to the inverter.

well if a diode wont work, i suppose then ill just have a small relay hold the connection between the capacitors and inverter during charge stage

i have a circuit board from a crt TV, that should have some thousand volt capacitors on it with relatively low capacity, ill try using them.

Again though, what will happen if i overcharge the capacitor? i always just thought it stops accepting current when its full.

GrantX

Mon May 06 2013, 12:12PM

Registered Member #4074 Joined: Mon Aug 29 2011, 06:58AM
Location: Australia
Posts: 335

You cannot "overcharge" a capacitor - only overvolt it.

Remember: a capacitor can only be charged as high as it's supply voltage. A 12V dc supply can charge a cap up to 12 volts, regardless of how many farads it is. A 325V supply will charge the same capacitors to 325V (if they are rated that high).

The two basic characteristics of a capacitor is it's capacitance (Farads, a measurement of surface area and distance between the plates) and the strength of its dielectric (voltage rating).

EDIT: So yes, you are correct. The current will simply stop flowing once the capacitor is charged up to the supply voltage.

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