3 Phase current usage

[Warren]

I need to estimate my factory current requirement as a result of moving to
a new premises. The electricity bill states 30000kWhr/month and there is no
instrumentation on the main switchboard apart from usage.

Can I estimate current requirements for the new factory like so


30000/(20*8)=187.5kW

then I=P/V so I=187500/415=452 amp

so 150 amp/phase on average

 

[Phil Allison]

"Warren"

I need to estimate my factory current requirement as a result of moving to
a new premises. The electricity bill states 30000kWhr/month and there is
no
instrumentation on the main switchboard apart from usage.

Can I estimate current requirements for the new factory like so

30000/(20*8)=187.5kW

then I=P/V so I=187500/415=452 amp

so 150 amp/phase on average

** What on earth use is it to know the AVERAGE current consumption ??

For all practical purposes (ie incoming service and breaker amp ratings )
you need to know the MAXIMUM current draw that occurs at any time and lasts
for even a few seconds.

Better get yourself an AC clamp meter and do some testing with everything
going at once.


..... Phil

 

[David]

On 27/04/2010 11:12 AM, Warren wrote:

I need to estimate my factory current requirement as a result of moving to
a new premises. The electricity bill states 30000kWhr/month and there is no
instrumentation on the main switchboard apart from usage.

Can I estimate current requirements for the new factory like so


30000/(20*8)=187.5kW

then I=P/V so I=187500/415=452 amp

so 150 amp/phase on average

If you are using the line to line voltage (415) you need to divide by
sqrt(3) not 3 to get the phase current. You also need to take into
account power factor, so the current will be much higher than 150A/phase.

You will actually need to do a proper maximum demand calculation, as
described in AS3000. This will take all your loads and their diversity
into account. Your energy supplier will probably require this
information for the connection anyway.

David

 

[Geoff C]

"Phil Allison" <phil_a@tpg.com.au> wrote in
news:83mvv6Fb5dU1@mid.individual.net:

"Warren"
I need to estimate my factory current requirement as a result of
moving to
a new premises. The electricity bill states 30000kWhr/month and there
is no
instrumentation on the main switchboard apart from usage.

Can I estimate current requirements for the new factory like so

30000/(20*8)=187.5kW

then I=P/V so I=187500/415=452 amp

so 150 amp/phase on average


** What on earth use is it to know the AVERAGE current consumption ??

For all practical purposes (ie incoming service and breaker amp
ratings ) you need to know the MAXIMUM current draw that occurs at any
time and lasts for even a few seconds.

Better get yourself an AC clamp meter and do some testing with
everything going at once.


.... Phil

OK.

 

[Noodnik]

"David" <david@usenet.com> wrote in message
news:000c19f2$0$1722$c3e8da3@news.astraweb.com...

On 27/04/2010 11:12 AM, Warren wrote:
I need to estimate my factory current requirement as a result of moving
to
a new premises. The electricity bill states 30000kWhr/month and there is
no
instrumentation on the main switchboard apart from usage.

Can I estimate current requirements for the new factory like so


30000/(20*8)=187.5kW

then I=P/V so I=187500/415=452 amp

so 150 amp/phase on average

If you are using the line to line voltage (415) you need to divide by
sqrt(3) not 3 to get the phase current. You also need to take into account
power factor, so the current will be much higher than 150A/phase.

You will actually need to do a proper maximum demand calculation, as
described in AS3000. This will take all your loads and their diversity
into account. Your energy supplier will probably require this information
for the connection anyway.

David

And if you have any significant electric drives with direct-on-line

starting, remember that the starting current can be up to 6 times full load
current. If you don't consider transients you could well end up with a
system that trips out regularly.

 

[Jasen Betts]

On 2010-04-27, Warren <not@mail.com> wrote:

I need to estimate my factory current requirement as a result of moving to
a new premises. The electricity bill states 30000kWhr/month and there is no
instrumentation on the main switchboard apart from usage.

Can I estimate current requirements for the new factory like so


30000/(20*8)=187.5kW


then I=P/V so I=187500/415=452 amp

you can't do that without knowing the power factor.

so 150 amp/phase on average

yeah, but the electric company probably wants to know peak, and that
that will determine the fuse they fit,

the best move is probably to go to the warehouse and grab one of their
cheap clamp ammeters and measure the current yourself

or call your electrician and get him/her to do it,


--- news://freenews.netfront.net/ - complaints: news@netfront.net ---

 

[Phil Allison]

"Jasen Betts" <jasen@xnet.co.nz>

the best move is probably to go to the warehouse and grab one of their
cheap clamp ammeters and measure the current yourself

** Thank GOD the sheep shagging Calvary has finally arrived !!

Better late than never......





.... Phil