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  1. #1
    Hi guys, I have built a motorcycle paddock starter on my 6040 CNC using a 180v 1HP 6 amp DC tread mill motor but the switch mode 240v AC to 180v 8 amp DC power supply cuts out (safety reset) when I put it under load trying to start a bike. I donít need to vary the speed, just run the motor at max for a few seconds at a time. So does anyone know can I use 240 AC through a 50A 1000V Metal Case Single Phases Diode Bridge Rectifier KBPC5010 and maybe a large capacitor on the motor side or am I doing something stupid?
    Cheers


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  2. #2
    Sterob's Avatar
    Lives in Australind, Australia. Last Activity: 19 Hours Ago Has been a member for 0-1 years. Has a total post count of 70. Received thanks 4 times, giving thanks to others 5 times.
    I'm not sure your treadmill motor would last too long, even if you are using it in short bursts.....
    I'd be tempted to use a a step down transformer and then rectify and smooth the output.
    Do you know what sort of power you would need to start a bike?

    If you use 180 V or just below, that will give you the best chance of success, I guess.

    Its all specultion, of course....lol

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  4. #3
    Quote Originally Posted by Smokie555 View Post
    Hi guys, I have built a motorcycle paddock starter on my 6040 CNC using a 180v 1HP 6 amp DC tread mill motor but the switch mode 240v AC to 180v 8 amp DC power supply cuts out (safety reset) when I put it under load trying to start a bike. I donít need to vary the speed, just run the motor at max for a few seconds at a time. So does anyone know can I use 240 AC through a 50A 1000V Metal Case Single Phases Diode Bridge Rectifier KBPC5010 and maybe a large capacitor on the motor side or am I doing something stupid?
    Cheers


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    Clearly depends on the bike as to what current will be needed . Maybe the best route is a motorbike starter and battery . There are some kits on Eboy

    https://www.ebay.co.uk/sch/i.html?_f...addock+starter

    Depends if you just want a paddock starter or maybe an "on the road" job too.
    We added a home brewed kit to our old BSA B31 which was a pig to restart if it stalled on the road

  5. #4
    The reason for the trip out will be that the motor takes WAY more than it's normal running 6A on startup: I have a rather similar motor here (1.25HP continuous, 1.75 intermittent) and it draws about 18A when starting from still. Ideally you want a power supply that ramps up it's output at a sensible rate, or one with constant-current limiting which will have something like the same effect. Your simple bridge supply thing might work if used for a short period, but you'll be properly caning the motor as the cap will charge to about 325V off load, nearly twice what the motor is rated at =4x the power. And if you do try it remember you will have NO mains isolation (though the 325V DC is a lot more dangerous than mains anyway), so Sterob's suggestion of a stepdown transformer is a good idea.
    A little while back there was a guy from Hungary that was selling some nice PWM DC motor controllers on the Bay of fleas for around £100, with current limiting, soft start etc., unfortunately I can't see them there at the mo. though eBay seem to have been fiddling with their search engine of late (WHY???) so it may be that's the reason. If I find a link I'll post it up here.
    Last edited by Voicecoil; 28-06-2020 at 07:13 PM.

  6. #5
    Quote Originally Posted by Voicecoil View Post
    The reason for the trip out will be that the motor takes WAY more than it's normal running 6A on startup: I have a rather similar motor here (1.25HP continuous, 1.75 intermittent) and it draws about 18A when starting from still. Ideally you want a power supply that ramps up it's output at a sensible rate, or one with constant-current limiting which will have something like the same effect. Your simple bridge supply thing might work if used for a short period, but you'll be properly caning the motor as the cap will charge to about 325V off load, nearly twice what the motor is rated at =4x the power. And if you do try it remember you will have NO mains isolation (though the 325V DC is a lot more dangerous than mains anyway), so Sterob's suggestion of a stepdown transformer is a good idea.
    A little while back there was a guy from Hungary that was selling some nice PWM DC motor controllers on the Bay of fleas for around £100, with current limiting, soft start etc., unfortunately I can't see them there at the mo. though eBay seem to have been fiddling with their search engine of late (WHY???) so it may be that's the reason. If I find a link I'll post it up here.
    Thanks, I was worried about the isolation problem and didn't know about the voltage build up. I got a 30Amp DC drive from AliExpess for $89 (took months to arrive) but it works great with its soft start. Thanks for the advice and here's a link if anyone has the same problem. https://www.aliexpress.com/item/3266...39a54c4dY7LOis

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    Cheers

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