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Old 06-03-2011, 10:24 PM   #1
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Power consumption in a power strip.


Hi,
Isn't there a practical limit on how many sockets you can have in a power strip ?

Given that AC power is P=VI(cosφ), each socket in the strip will consume P supplied from one single wall socket. That means, the wall socket will have to deliver as much current as required by all the sockets in the strip. And, therefore, the number of sockets that can be supported is dependent on the number of Ampere limit of a house-hold.

Is this correct ?
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Old 06-04-2011, 12:34 AM   #2
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Power consumption in a power strip.


The sockets themselves don't consume any power, only loads actually connected to them. Whatever loads are plugged into the power strip are all aggregated onto the one plug for the power strip. So, it's easy to overload a power strip by plugging in too many high-current loads. If all of the loads are low-current (like DC adapters or small battery chargers, for example), then it's not a problem.

So there is no practical limit on how many receptacles there can be, only on how much total load can be connected.
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Old 06-04-2011, 08:34 AM   #3
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Power consumption in a power strip.


Keep in mind that the power strip is plugged into a conventional receptacle that has a current limit determined by the breaker protecting that circuit. Also, the power strips available on today's market all have a circuit breaker so the current draw to the strip is limited by this device.
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Old 06-04-2011, 08:35 AM   #4
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Power consumption in a power strip.


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Originally Posted by mpoulton View Post
So there is no practical limit on how many receptacles there can be, only on how much total load can be connected.
Maybe things work differently for those 50 cycle types.
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Old 06-04-2011, 10:08 PM   #5
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Power consumption in a power strip.


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Originally Posted by mpoulton View Post
The sockets themselves don't consume any power, only loads actually connected to them. Whatever loads are plugged into the power strip are all aggregated onto the one plug for the power strip.
But, of course.

Quote:
Keep in mind that the power strip is plugged into a conventional receptacle that has a current limit determined by the breaker protecting that circuit. Also, the power strips available on today's market all have a circuit breaker so the current draw to the strip is limited by this device.
Yes. But, if there were no circuit breakers in the power strip, then the power strip cannot be drawing arbitrarily huge amperes of current without tripping the MCB. So, I wanted to know, can I calculate that ampere limit ?
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Old 06-04-2011, 11:46 PM   #6
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Power consumption in a power strip.


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Originally Posted by AC230V50Hz View Post
Yes. But, if there were no circuit breakers in the power strip, then the power strip cannot be drawing arbitrarily huge amperes of current without tripping the MCB. So, I wanted to know, can I calculate that ampere limit ?
It's whatever the rating of the circuit breaker for that branch circuit is, less any other loads on the circuit. So if it's a 15A circuit, then your power strip can use up to 15A, less any other loads. Maybe I'm misunderstanding the question?
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Old 06-05-2011, 04:38 AM   #7
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Power consumption in a power strip.


Flip it over and look at the spec.label.
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Old 06-06-2011, 12:36 AM   #8
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Power consumption in a power strip.


Quote:
Maybe I'm misunderstanding the question?
Perhaps, I am not writing the question correctly.

The wall socket would deliver 230 V AC at 5 A. If I plug in a power strip to the wall socket, with sockets in power strip, each requiring to deliver 230 V at 5 A, then how many such sockets can I have in my power strip ? I think, the limit is applied by the fuse in the power strip. That would mean, the actual ampere value is determined by whatever is the specification for that power strip.

Now, for argument sake, if I have a power strip with no fuse, then the limit is applied by MCB of the house (assume no other electrical load in house). If so, then the actual ampere value is determined by whatever is the specification for house MCB. Is this correct ?
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Old 06-06-2011, 12:55 AM   #9
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Power consumption in a power strip.


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Originally Posted by AC230V50Hz View Post
Perhaps, I am not writing the question correctly.

The wall socket would deliver 230 V AC at 5 A. If I plug in a power strip to the wall socket, with sockets in power strip, each requiring to deliver 230 V at 5 A, then how many such sockets can I have in my power strip ? I think, the limit is applied by the fuse in the power strip. That would mean, the actual ampere value is determined by whatever is the specification for that power strip.

Now, for argument sake, if I have a power strip with no fuse, then the limit is applied by MCB of the house (assume no other electrical load in house). If so, then the actual ampere value is determined by whatever is the specification for house MCB. Is this correct ?
A 15 amp circuit breaker will handle up to 15 amps (that's 1400 W after an 80% Derating) P= I*E where E=120v (not 230), and I=15a
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Old 06-06-2011, 03:00 AM   #10
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Power consumption in a power strip.


Quote:
Originally Posted by AC230V50Hz View Post
Perhaps, I am not writing the question correctly.

The wall socket would deliver 230 V AC at 5 A. If I plug in a power strip to the wall socket, with sockets in power strip, each requiring to deliver 230 V at 5 A, then how many such sockets can I have in my power strip ? I think, the limit is applied by the fuse in the power strip. That would mean, the actual ampere value is determined by whatever is the specification for that power strip.

Now, for argument sake, if I have a power strip with no fuse, then the limit is applied by MCB of the house (assume no other electrical load in house). If so, then the actual ampere value is determined by whatever is the specification for house MCB. Is this correct ?
The individual sockets in the power strip can each supply the full capacity of the circuit (all 5A, or whatever) - but that will only happen if you plug a load into one of them that actually draws the full current. Usually the loads are much smaller, so you can run many loads at a time on the circuit (hence the need for a power strip - to plug in many small things at once). So there is no limit on how many sockets you can have, only a limit on the total load you can plug into them.
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Old 06-06-2011, 07:42 AM   #11
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Power consumption in a power strip.


The voltage and frequencies are typical for a European system.
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Old 06-06-2011, 07:55 AM   #12
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Power consumption in a power strip.


Quote:
Originally Posted by AC230V50Hz View Post
Perhaps, I am not writing the question correctly.

The wall socket would deliver 230 V AC at 5 A. If I plug in a power strip to the wall socket, with sockets in power strip, each requiring to deliver 230 V at 5 A, then how many such sockets can I have in my power strip ? I think, the limit is applied by the fuse in the power strip. That would mean, the actual ampere value is determined by whatever is the specification for that power strip.

Now, for argument sake, if I have a power strip with no fuse, then the limit is applied by MCB of the house (assume no other electrical load in house). If so, then the actual ampere value is determined by whatever is the specification for house MCB. Is this correct ?
If I understand correctly then you can only use one socket.

You are limited to 5 amps by the socket fuse. You can only plug in one 5 amp load in the power strip.
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