27 May
2009
27 May
'09
4:06 p.m.
I have seen the specs for input current for various power supplies.
Obviously, the higher the maximum output current, the higher the
rated input current.
I would like to buy a power supply that is about double the usual
capacity that I will need, but I am wondering how this choice
might affect the UPS up time when the street power fails?
If the load for two power supplies is the same, will the input current
be similar if the maximum output rating of one power supply is
double the other power supply, assuming that the load is within
the rating of the smaller power supply?
Sincerely yours,
Jerome Fine
27 May
27 May
5:08 p.m.
On 27/05/2009 17:06, Jerome H. Fine wrote:
If the load for two power supplies is the same, will
the input current
be similar if the maximum output rating of one power supply is
double the other power supply, assuming that the load is within
the rating of the smaller power supply?
Assuming they have about the same percentage efficiency, yes, the
current draw will be the same for the same load. And therefore the UPS
autonomy (uptime) will be the same.
--
Pete Peter Turnbull
Network Manager
University of York
7:35 p.m.
Jerome H. Fine wrote:
I would like to buy a power supply that is about
double the usual
capacity that I will need, but I am wondering how this choice
might affect the UPS up time when the street power fails?
A switching power supply
does become less efficient at low load. A
switcher that is 80% efficient at rated load might only be 60% efficient
at half load. However, there's no general way to determine the
efficiencies for a particular supply except to check the specs (which
often don't have that information), or to measure it.
Eric
7:48 p.m.
I have seen the specs for input current for various power supplies.
Obviously, the higher the maximum output current, the higher the
rated input current.
I would like to buy a power supply that is about double the usual
capacity that I will need, but I am wondering how this choice
might affect the UPS up time when the street power fails?
If the load for two power supplies is the same, will the input current
be similar if the maximum output rating of one power supply is
double the other power supply, assuming that the load is within
the rating of the smaller power supply?
This depends on the efficiency of the power supplies, which is basically
defined as the ration of output power to input power. This efficiency
obviously depends on the design of the power supply (linears are a lot
worse than switchets) and to some extend on the maximum power rating of
the PSU. But for the supplies you're thinking of, it's likely to be
pretty much the same.
In whcih case for a given output power (that is, for the same load
connected to the PSU), the input power is going to be much the same no
matter which PSU you use. And thus the amount of time your UPS will run
it for is going to be much the same
-tony
11:42 p.m.
Tony Duell wrote:
If the load for
two power supplies is the same, will the input current
be similar if the maximum output rating of one power supply is
double the other power supply, assuming that the load is within
the rating of the smaller power supply?
This depends on the efficiency of the power supplies, which is basically
defined as the ration of output power to input power. This efficiency
obviously depends on the design of the power supply (linears are a lot
worse than switchets) and to some extend on the maximum power rating of
the PSU. But for the supplies you're thinking of, it's likely to be
pretty much the same.
In whcih case for a given output power (that is, for the same load
connected to the PSU), the input power is going to be much the same no
matter which PSU you use. And thus the amount of time your UPS will run
it for is going to be much the same
5707
days inactive
5707
days old
4 comments
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participants (4)
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ard＠p850ug1.demon.co.uk -
eric＠brouhaha.com -
jhfinedp3k＠compsys.to -
pete＠dunnington.plus.com