In the datasheet of the smps supply, I have found that the inrush current of the supply is 40A. But the time period of the inrush current is not provided in the datasheet. Is there any way to find the inrush time period using the specifications in the datasheet or is there any constant time period for the inrush current (eg. 50ms)? Also I have seen the two terms "setup time", "rise time" and "hold-up time" in the datasheet. Please explain those terms in detail.
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kailash kumaravel
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Please provide a link to the pdf data sheet. If there isn't one or you are buying from an unreputable supplier then you are probably not going to get a decent answer. – Andy aka Dec 24 '19 at 09:01
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Is there any way to find the inrush time period using the specifications in the datasheet
No. The datasheet only provides the height of the inrush current (20A or 40A), not the duration.
The duration depends on the size of the input capacitor.
(Image source: https://sound-au.com/articles/inrush.htm)
the [...] terms "setup time", "rise time" and "hold-up time"
They apply to the output.
In the picture above, t2 is the rise time and t1+t2 is the setup time.
The hold time is time when the input drops below the minimum input voltage to when the output voltage drops below its minimum regulated output tolerance.
Image and recommended source: httpsy://www.testandmeasurementtips.com/test-dc-dc-converters/
Huisman
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Inrush is always worst case abrupt turn on at peak input voltage.
- as the function is to charge up primary line voltage to a storage cap, the current will exponentially decay to some steady state value
- so there is no specific duration at peak current, but there could be a duration for 50% of worst case peak, not given but I would estimate ~1 cycle
- the inrush is twice on 240V due to peak voltage yet 1/2 the avg run current due to equivalent power so it will decay quickly and storage holdup is 1cycle at rated power.
Are your worried about premature breaker trips?
Although 30A Breaker is needed for 10x 3A @ 240Vac 50Hz ,
a good breaker should not trip @ 30x breaker rating in 1 cycle. AWG 10 or better.
Tony Stewart EE75
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Yes sir, I have to connect ten of this supply to a single breaker. So I assume that the total inrush current will be 400A. So if I want to choose a right breaker, what will be the specifications of that breaker? Whether it should be rated to 400A capacity or can a breaker with lesser current rating withstand that inrush current for a specific time without tripping? – kailash kumaravel Dec 24 '19 at 06:27
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If you are worried about 3 phase imbalanced loads after power interruption , split the load on 3 phases or use some other protection like a ZCS Triac with a timer RELAY BYPASS – Tony Stewart EE75 Dec 24 '19 at 07:43