# DC Power supply rating

Discussion in 'General Electronics Chat' started by superway, May 14, 2015.

1. ### superway Thread Starter Active Member

Oct 19, 2009
128
0
Hello,
I looked many websites, sometimes I see a DC supply 60V/80A the output rating up to 1200W.
But sometimes I see DC supply 60V/80A and the Output rating more than 3000W.
What is the difference between of them, even they have the same Voltage and Current?
Thanks,
Ken

2. ### dl324 Distinguished Member

Mar 30, 2015
3,106
599
There should be no difference, both should have the same power rating. Can you cite some examples?

Jan 15, 2015
958
225
Watts = Volts * Amps

A power supply rated to deliver 60V @ 80 Amps is a 4,800 Watt supply. I would have to read the data sheet(s) on any other supplies you are speaking of.

Ron

Apr 5, 2008
15,528
2,300
Hello,

Do you have links to datasheets of the mentioned power supplies?
A 1200 Watt power supply will give a max current of 20 Amps at 60 volts and will deliver 15 Volts at 80 Amps.

Bertus

5. ### ian field Distinguished Member

Oct 27, 2012
4,314
768
Don't forget a small difference between input and output power.

A switcher should be 80% efficient at the very worst - but I doubt that would account for the difference the TS stated, unless one of them was linear.

6. ### dl324 Distinguished Member

Mar 30, 2015
3,106
599
The power rating should be what the output can provide to a load.

7. ### ian field Distinguished Member

Oct 27, 2012
4,314
768
You have to watch out when skimming over adverts - often one or the other power specification is in the small print, or not mentioned at all.

Jan 15, 2015
958
225
Yes, good point but I haven't a clue where the OP is getting his numbers. This is why I always ask for a data sheet, even one written in Chinglish.

Ron

9. ### crutschow Expert

Mar 14, 2008
12,522
3,064
It would seem that neither supply can deliver both the maximum current and maximum voltage at the same time.
Thus the power output (output voltage times the current) can't be more than its power rating.

mcgyvr likes this.
10. ### superway Thread Starter Active Member

Oct 19, 2009
128
0
Thanks for your inputs. Here are the screenshots to show the power ratings, 60V @50A , 1000W. It is not W = VI

11. ### ScottWang Moderator

Aug 23, 2012
4,781
759
1. Vo=Wmax/Imax=1000W/50A=20V
It means that when you want to using the Imax 50A then you only can be use with 20V.
Because the Wmax is limited in 1000W, so you have to using Wmax to divide by Imax 50A.

2. Vo=Wmax/Imax==1200W/50A= 24V
It means that when you want to using the Imax 50A then you only can be use with 24V.
Because the Wmax is limited in 1200W, so you have to using Wmax to divide by Imax 50A.

12. ### superway Thread Starter Active Member

Oct 19, 2009
128
0
Thanks. How about this model below; it is rated 60A, 85A, 51000W. That is W = 60 x 85 = 5100W. So It is different my previous screenshots ?

13. ### ScottWang Moderator

Aug 23, 2012
4,781
759
Yes, they are different, so this kind of type will be more expensive.

14. ### ScottWang Moderator

Aug 23, 2012
4,781
759
Some power supplies was designed for the output by wattage, it means that the V/I output will be combined and limited by Watt, maybe this is the one.

15. ### mcgyvr AAC Fanatic!

Oct 15, 2009
4,730
963
Yep its UP to 60V and UP to 80A with UP to being important.. You just can't do both at the same time as its limited to how much power it can dissipate
You can really only do 20A @ 60V..(1200W) or 80A @ 15V (1200W) or any combination that doesn't exceed 1200W

16. ### crutschow Expert

Mar 14, 2008
12,522
3,064
Yes. Note that you will need a special high current mains outlet to power that supply as it takes up to 24A @ 230Vac at its rated power.

17. ### ian field Distinguished Member

Oct 27, 2012
4,314
768
IIRC: the cooker point is usually rated about 30A or so.

18. ### ScottWang Moderator

Aug 23, 2012
4,781
759
Th posted in #11 were used the max current, the similar when we using the max voltage then the current will be as these:

1. Io=Wmax/Vmax=1000W/60V=16.67A
It means that when you want to using the 60 Vmax then you only can be use 16.67A current.
Because the Wmax is limited in 1000W, so you have to using Wmax to divide by 60 Vmax.

2. Io=Wmax/Vmax==1200W/60V= 20A
It means that when you want to using the 60 Vmax then you only can be use 20A current.
Because the Wmax is limited in 1200W, so you have to using Wmax to divide by 60 Vmax.