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Thread: How to simulate arc lamp to test power supply?

  1. #1
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    Default How to simulate arc lamp to test power supply?

    Hi PhotonLexicon,

    I bought an arc lamp pumped laser , but there are some power supply and interfacing problems. How can I test the power supply without connecting the laser head? I want to simulate the arc lamp without having to connect the real laser head and all of the associated cooling (I calculate the arc lamp needs to dissipate about 4kW).

    Since the arc lamp has a negative resistance characteristic, the power supply must be current controlled, so is it safe to simply short the output? I noticed there is a large fuse in series with the arc lamp so perhaps not. Can I buy a cheap surplus arc lamp of a similar but different type, and run it in a bucket of water with reduced power? Otherwise, what sort of dummy load can I use in place of the arc lamp?

    Thanks,

    weartronics

  2. #2
    mixedgas's Avatar
    mixedgas is online now Creaky Old Award Winning Bastard Technologist
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    if you remove the 1000V start boost circuit and the ignitor, you could run a 7 ohm water cooled resistor in series with a diode. , the lamps have a habit of explodinging if not in the cooling flow tube in the head, from cavitation at the anode from lack of pressure. lamp in bucket with no tight wraparound flow = spectacular explosion.

    the resistor however will kill the boost and ignitor circuits if not disabled.

    you need 1-1.5 Kv@ 10-100 ma across the lamp to start , called boost, plus the ignite pulse.

    hence no easy direct resistive loads.

    Steve

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    Hi Steve, thanks for your info. I have to inspect the power supply, but from memory there is one capacitor for the boost circuit that I can remove, and the igniter circuit is one loop of wire around a large inductor in series with the lamp, I can put the loop of wire somewhere else. Regards, weartronics

  4. #4
    mixedgas's Avatar
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    big electric water heater elements come to mind. Do you have single phase electric water heaters in oz? watch out for the huge inductance in water heater elements, one wouldnt think there would be much in a simple resitive heater, but because of the way they are wound, there is half a Henry or so, hence the blocking diode in series. otherwise the inductive kick when you turn OFF the supply blows the output stage. Learned that the hard way doing similar tests

    Steve

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    Quote Originally Posted by mixedgas View Post
    if you remove the 1000V start boost circuit and the ignitor, you could run a 7 ohm water cooled resistor in series with a diode. , the lamps have a habit of explodinging if not in the cooling flow tube in the head, from cavitation at the anode from lack of pressure. lamp in bucket with no tight wraparound flow = spectacular explosion.

    the resistor however will kill the boost and ignitor circuits if not disabled.

    you need 1-1.5 Kv@ 10-100 ma across the lamp to start , called boost, plus the ignite pulse.

    hence no easy direct resistive loads.

    Steve
    I think boost voltage source and trigger circuit is protected from 7Ohm load resistance, so there should not be any harm.
    Besides, when You connect the dummy load then put PS to ready mode, no start pulsing should be required.The PS will see the main current flowing, but if You don't have separate READY and TRIGGER switches, the trigger pulse may hard to avoid in this PS.
    Remember that removing the cap from boost won't remove high voltage. There should be a ca 20ohm resistor after the boost cap that if removed would keep boost voltage away from Your PS output.

    Piotr.K

  6. #6
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    Quote Originally Posted by mixedgas View Post
    big electric water heater elements come to mind. Do you have single phase electric water heaters in oz?

    Steve
    Yes we do, they run off 240V with usually something like a 32A breaker. Ive rarely seen any 2 or 3 phase hot water heaters for houses around here.

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