| Author |
AC current direction
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| Warren Thai 2007-10-10, 3:25 am |
| I'm designing a system to inject an AC current into an AC bus. I'm trying to
get my head around something. To get current injected INTO the bus, would
the current have to be in phase or 180degrees out of phase with the voltage?
At first thought it would be to have it in phase but if you think about
this: Take an AC voltage and apply to a resistor. The current is in phase
with the voltage and current flows from voltage to resistor so it would make
sense that to inject current 180degrees out of phase, the current will go
into the bus. Is this correct?
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| Tim Perry 2007-10-10, 3:25 am |
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"Warren Thai" <wthai1@optusnet.com.au> wrote in message
news:470c7f35$0$7087$afc38c87@news.optusnet.com.au...
> I'm designing a system to inject an AC current into an AC bus. I'm trying
to
> get my head around something. To get current injected INTO the bus, would
> the current have to be in phase or 180degrees out of phase with the
voltage?
> At first thought it would be to have it in phase but if you think about
> this: Take an AC voltage and apply to a resistor. The current is in phase
> with the voltage and current flows from voltage to resistor so it would
make
> sense that to inject current 180degrees out of phase, the current will go
> into the bus. Is this correct?
>
Can you explain a little further on what you mean by "inject an AC current
into an AC bus"?
What are you trying to accomplish?
The more current and voltage are "out of phase" the worse your power factor
(PF) becomes.
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| Warren Thai 2007-10-10, 9:25 am |
| What i mean by injecting an AC current into an AC bus is this. If you
connect a load to the bus, that load takes AC current from the grid. I'm
trying to put more AC current onto the bus.
"Tim Perry" <timperry@nospammeadelphia.net> wrote in message
news:470c8670$0$32489$4c368faf@roadrunner.com...
>
> "Warren Thai" <wthai1@optusnet.com.au> wrote in message
> news:470c7f35$0$7087$afc38c87@news.optusnet.com.au...
> to
> voltage?
> make
>
> Can you explain a little further on what you mean by "inject an AC
> current
> into an AC bus"?
> What are you trying to accomplish?
>
> The more current and voltage are "out of phase" the worse your power
> factor
> (PF) becomes.
>
>
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| Palindrome 2007-10-10, 9:25 am |
| Warren Thai wrote:
> What i mean by injecting an AC current into an AC bus is this. If you
> connect a load to the bus, that load takes AC current from the grid. I'm
> trying to put more AC current onto the bus.
What it sound like you are trying to do is to parallel a generator with
an existing bus. Try researching that - there are loads of stuff on the
internet about it.
--
Sue
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| Don Kelly 2007-10-10, 8:25 pm |
|
----------------------------
"Warren Thai" <wthai1@optusnet.com.au> wrote in message
news:470c7f35$0$7087$afc38c87@news.optusnet.com.au...
> I'm designing a system to inject an AC current into an AC bus. I'm trying
> to get my head around something. To get current injected INTO the bus,
> would the current have to be in phase or 180degrees out of phase with the
> voltage? At first thought it would be to have it in phase but if you think
> about this: Take an AC voltage and apply to a resistor. The current is in
> phase with the voltage and current flows from voltage to resistor so it
> would make sense that to inject current 180degrees out of phase, the
> current will go into the bus. Is this correct?
-----------------
Yes, a load will draw a current from the bus- and this current will depend
on the load and the bus voltage. You don't "inject" a current. If the load
changes then its current will change.
Whatever current that loads draw from the bus is determined by the
loads -all the sources do is
If you are wanting to connect another source to the bus then, as suggested
by Palindrome, look at parallel operation of generators and load sharing
between generators. A bit more circuit theory might also help before you try
to "design" something.
In connecting the incoming generator it is necessary to match the <voltage>
magnitude and phase to that of the bus. If done correctly, there is no
current. If the voltage magnitude of the incoming generator is increased,
the main effect will be a shifting of reactive from the other sources on the
bus (not affecting the load except for secondary effects) not always what
you want. If you try to speed up the machine you will advance the phase of
the voltage (by a small amount, please) and some of the total power will be
provided by this machine- again without changing the load current or power.
Either way will result in a current from the incoming machine. It is better
to think of complex power flows than currents.
--
Don Kelly dhky@shawcross.ca
remove the X to answer
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| Tim Perry 2007-10-11, 3:25 am |
|
"Warren Thai" <wthai1@optusnet.com.au> wrote in message
news:470ca042$0$12802$afc38c87@news.optusnet.com.au...
> What i mean by injecting an AC current into an AC bus is this. If you
> connect a load to the bus, that load takes AC current from the grid. I'm
> trying to put more AC current onto the bus.
>
Way back at the dawn of the computer age there was a FORTRAN IV based
program called ECAP. This "modeled' an electronic circuit by breaking down
all electronic components into inductive and capacitive reactance's plus
resistance. It also provided for current and voltage sources.
If you use this or one of its more modern cousins you can plug in different
values and have it calculate the results.
If you try a "lab" experiment with real AC power you are likely to hurt
someone real bad.
I'd recommend your attention to
http://free-ed.net/sweethaven/ModElec/acee/default.asp
for a start in AC theory.
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| Michael A. Terrell 2007-10-11, 9:25 am |
| Tim Perry wrote:
>
> "Warren Thai" <wthai1@optusnet.com.au> wrote in message
> news:470ca042$0$12802$afc38c87@news.optusnet.com.au...
>
> Way back at the dawn of the computer age there was a FORTRAN IV based
> program called ECAP. This "modeled' an electronic circuit by breaking down
> all electronic components into inductive and capacitive reactance's plus
> resistance. It also provided for current and voltage sources.
If you are talking about a 'SPICE' program, there are plenty of free
programs out there.
http://www.linear.com/software/ is a popular program.
--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.
Michael A. Terrell
Central Florida
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| Tim Perry 2007-10-11, 1:25 pm |
|
"Michael A. Terrell" <mike.terrell@earthlink.net> wrote in message
news:470E1A3E.7063002F@earthlink.net...
> Tim Perry wrote:
I'm[color=darkred]
down[color=darkred]
>
>
> If you are talking about a 'SPICE' program, there are plenty of free
> programs out there.
>
> http://www.linear.com/software/ is a popular program.
>
>
> --
> Service to my country? Been there, Done that, and I've got my DD214 to
> prove it.
> Member of DAV #85.
>
> Michael A. Terrell
> Central Florida
And it probably doesn't use punch cards either <g>
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| Michael A. Terrell 2007-10-12, 9:25 am |
| Tim Perry wrote:
>
> "Michael A. Terrell" <mike.terrell@earthlink.net> wrote in message
> news:470E1A3E.7063002F@earthlink.net...
>
> And it probably doesn't use punch cards either <g>
How many days would it take to load a program that big? 
--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.
Michael A. Terrell
Central Florida
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| gfretwell@aol.com 2007-10-12, 1:25 pm |
| On Fri, 12 Oct 2007 06:21:14 -0400, "Michael A. Terrell"
<mike.terrell@earthlink.net> wrote:
>
>
> How many days would it take to load a program that big?
>
A typical "txt" card (the format for loading programs) had about 60
bytes of object code on it so say 60,000 bytes a minute. (2540 or 2501
card reader)
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| In article <1u1vg3hk4qenkueq9cj54jlsffn84n9sm3@4ax.com>,
gfretwell@aol.com says...
> On Fri, 12 Oct 2007 06:21:14 -0400, "Michael A. Terrell"
> <mike.terrell@earthlink.net> wrote:
>
> A typical "txt" card (the format for loading programs) had about 60
> bytes of object code on it so say 60,000 bytes a minute. (2540 or 2501
> card reader)
Also figure that memory was rarely larger than that and processors
weren't exactly swift either.
--
Keith
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| Michael A. Terrell 2007-10-12, 9:25 pm |
| krw wrote:
>
> In article <1u1vg3hk4qenkueq9cj54jlsffn84n9sm3@4ax.com>,
> gfretwell@aol.com says...
>
> Also figure that memory was rarely larger than that and processors
> weren't exactly swift either.
Don't forget the room full of low density 9 track tape drives.
The product would be obsolete before you could finish the simulation.
;-)
--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.
Michael A. Terrell
Central Florida
| |
|
| In article <4710285C.60EF9739@earthlink.net>,
mike.terrell@earthlink.net says...
> krw wrote:
>
>
> Don't forget the room full of low density 9 track tape drives.
>
>
> The product would be obsolete before you could finish the simulation.
> ;-)
Looking at it that way, things have actually slowed down! Products
are now obsolete before manufacturing even sees them. ;-)
--
Keith
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