Author Topic: lab psu's  (Read 315 times)

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Offline silly sausageTopic starter

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lab psu's
« on: January 16, 2025, 11:25:50 am »
I notice most variable lab power supplys are 0-30v, Why 30v and not say 50v,is there a reason or convention they all seem to be 30v max, I notice either linear or switchers are like this, Why is that so?.
 

Online wraper

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Re: lab psu's
« Reply #1 on: January 16, 2025, 11:45:13 am »
Generally more than 30V is rarely needed. When you increase voltage, you need to reduce maximum current if you make PSU with the same power rating, it's a tradeoff and 30V is basically a sweet spot for general use. Unlike 30V, 50V is dangerous and needs much more precaution when used.
 
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Offline radiolistener

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Re: lab psu's
« Reply #2 on: January 16, 2025, 12:02:49 pm »
30V is classified as safe voltage for humans, higher voltage may cause serious damage to your heart and may lead even to death.

As you probably know, for high-humidity environments such as showers, saunas, or swimming pools, electrical lighting operating at 36V AC is also used for the same reason - to ensure human safety.

Additionally, most electronic devices are designed to operate at standard voltages such as 3.3V, 5V, 6V, 8V, 9V, 12V, 13.8V, 14.4V, 18V, and 24V. Therefore, a 30V range covers the needs of nearly all such devices with a small margin.
« Last Edit: January 16, 2025, 12:05:13 pm by radiolistener »
 
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Offline Konkedout

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Re: lab psu's
« Reply #3 on: January 16, 2025, 07:47:01 pm »
30V is classified as safe voltage for humans, higher voltage may cause serious damage to your heart and may lead even to death.

As you probably know, for high-humidity environments such as showers, saunas, or swimming pools, electrical lighting operating at 36V AC is also used for the same reason - to ensure human safety.

Additionally, most electronic devices are designed to operate at standard voltages such as 3.3V, 5V, 6V, 8V, 9V, 12V, 13.8V, 14.4V, 18V, and 24V. Therefore, a 30V range covers the needs of nearly all such devices with a small margin.

I agree with all of the above.  I happen to have an old linear regulated Chinese made bench power supply.  It is 0-50V at 3 Amps. I THINK I purchased it from MPJA many years ago. I have never opened it up, but my ears tell me that it somehow uses relays to switch transformer taps as the output voltage is varied.  This would limit the power dissipation in the linear regulator.  This aspect works pretty well.

I do not like the current limiting characteristic as the output simply shuts down when the current limit is exceeded.  You cannot use the output current limit to set it as a constant current source.
Also the voltage adjustment potentiometer is noisy.  But this is probably a matter of using a cheap component rather than any issue with the architecture of the power supply.
« Last Edit: January 16, 2025, 07:49:37 pm by Konkedout »
 
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