Thread: PSU : prices and differences
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23-08-2013 #1
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23-08-2013 #2
Expensive ones free shipping, the cheap one you pay for shipping?
Cheap one is 230v only, expensive one does 110 or 230v.
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24-08-2013 #3
“There is nothing in the world that some man cannot make a little worse and sell a little cheaper, and he who considers price only is that man's lawful prey." John Ruskin
Dealt with Sure Electronics in distant past, they seemed pretty straight up and good value at the time, Meanwell are one of largest PSU makers in world, quality assurance has some costs.
Dealt with LED lighting for last 15 years, biggest cause of premature failure, bar none, is cheaping out on PSUs, there are some frankly scary power supplies out there, recovered from scrap and put in shiny case, assembled with half the parts missing, just plain assembled wrong and on more than one occasion have seen non passive faliures, ker -ferking-bang.
Genuine Meanwell is worth the extra for the piece of mind.
Cheers
Adam
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The Following User Says Thank You to Musht For This Useful Post:
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The Following User Says Thank You to Clive S For This Useful Post:
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24-08-2013 #5
Thank you guys,
if you are using it for steppers
a toroidal transformer might suit your needs better
Thanks
Gytis
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Well you could use something like this :- PS806-5 Linear power supply. or build one. it depends somewhat on the drive you will be using ...Clive
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24-08-2013 #7
Hi Gytis,
You'll be much better with Unregulated supply so I'd go with toroid and build your own has the linked one doesn't provide enough currant. For 4 * 3.5A steppers You'll need minimum 8A and that only provides 6A.
It's not difficult and if you want to take that route then email me about it and I'll explain what's needed and were to buy components. Won't reply for a couple of days thou has I'm away from home at moment.
Dean.
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24-08-2013 #8
Hi Dean and Thank you!
I'm a little bit confused right now..,
I have Gecko G540, and I decided to use these motors from cncrouterparts
so if you think that the toroidal transformers suit them better, then I'll go with your suggested route
Thank you
Gytis
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25-08-2013 #9
Re building a PSU from a toroidal transformer have a look at this thread
http://www.mycncuk.com/forums/showthread.php?p=35458
Its a bit long but everything you need to know is there. Then come back and ask about anything you don't understand.
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25-08-2013 #10
Ok no need to be confused buddy it's nothing special or difficult to get your head around. I'll explain for the sake of others thou it's all on the forum somewhere else.!
You have G540 which is limited to maximum 50Vdc and provides 3.5A for the motors. Now the Voltage is Fixed and you can't use higher than 50Vdc else you'll damage the G540, in real use you shouldn't actually run at 50Vdc has Steppers are like dynamo's and produce electricity when decelerating, some of this then gets passed back to the drives and if your running at the drives maximum it can easily push the voltage past drives threshold and blow it up.!!
Now the reason why Unregulated and toroidal PSU are better for steppers and much preferred to linear regulated PSU's is because when this excess electricity is produced some of it gets passed back to the PSU. Regulated PSU's tend to be very sensitive to this and have protection built in which trips the PSU and saves it's components. When this happens that's not the end and Electricity still needs to go somewhere so back it goes to Drives which can't handle it and either trip out if protected or BOOM.!! in less capable drives.!!
Now we can't have this has steppers are constantly doing this, esp under hard deceleration from higher speeds. So with Linear regulated PSU we need larger safety margin for the drives so instead of 50Vdc you'll want to run at 40-44Vdc maximum for safety sake.
Now with steppers Voltage makes a big difference to speed and torque you'll get from them so really we don't to waste any if we want peak performance..!!. . . . . Unregulated Toroidal supply works different and it's capacitors act like sponges so easily handle any returning electricity (provided enough spare capacitance is built in.!)
Now Because of these caps sucking up excess juice it also means we can use voltages very close to the Drives Maximum and 48Vdc could safely be used.
They also mean we don't need has high Amp supply because the capacitors hold a reserve of power and because the drives will only pull power during the PWM ON cycle there's plenty juice in reserve so less amps are required for several motors. Roughly 60-70% less. So for your 4 x 3.5A maximum requirements you'll only need Approx 8A not 14A you would with Regulated supply.
One other thing you or others may not know about the G540.? It's not limited to 3.5A motors.?
It can be used with higher currant motors but the drive will only provide 3.5A so you'll get reduced Torque than motors rating. On top of this you'll lose the auto currant reduction the gecko provides when motors are at rest. (There is a easy trick to get this back thou which involves using a resistor.?)
Get in touch if you want to build one.!!
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