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Registered Member #2008
Joined: Tue Mar 03 2009, 05:11AM
Location: USA, Frederick, MD
Posts: 118
I bought an electronic module that produces a 3kv output using a tiny transformer driven by 30KHZ.
The company tries to sell a power supply rated 12V 1amp. But they say that the circuit can be powered with up to 12v 1.5A I got a radioshack transformer. It outputs 12V, 3A max.
Do I need to find an operating current consumption of the circuit to know how to limit the current through the transformer?
Should I put a limiting resistor before the primary or after the secondary? (can be a capacitor since we are dealing with AC)
Can I use a dimmer switch from a lamp to limit current entering the transformer, or it would effect voltage or it is not advised to do at all?
It appears that this circuit cannot limit it's own current. Am I right? But I don't know what it's resistance is. I can play around with shunts but I want to know what resistance I am aiming at.
I can always write to the manufacturer. I just don't want to ask a lot of stupid questions.
Registered Member #146
Joined: Sun Feb 12 2006, 04:21AM
Location: Austin Tx
Posts: 1055
If the thing draws 1A at 12V then it has an apparent impedance of 12 ohms, if you supply it 12V it should still only use 1A regardless of if your power supply is capable of supplying 3A.
The only case where it might matter is if you short circuit the output of this device, it means that the 12V 1A supply probably sags to less than 12V (but still 1A) to reduce the power level, but your 3A supply will supply it with 3X the power.
Id power the thing up with the 3A supply and monitor the current draw to see if you really need any sort of current limiting, you may not.
Registered Member #2008
Joined: Tue Mar 03 2009, 05:11AM
Location: USA, Frederick, MD
Posts: 118
Smart idea. Thanks.
I was allready making a shunt for this purpose. Some things can limit current to themselves (like lightbulbs), while others (transistor bases and LEDs) destroy themselves and need an external resistor.
If I ever use a resistor it would be a capacitor on the primary.
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Bought a HV transformer circuit. I have to limit input to 1 AMP. Neet to know internal resistance?
