calculate the current of 3 phase motors

Thread Starter

dashhossein

Joined Jul 30, 2020
42
hello everyone
i'm kind of new to power electronics
I measured the current intensity with digital clamp meter and it show 22 A from the start time and after few second reach to 8.1 A
A question came to my mind that for example the 8 A is total current the motor use or should i multiple that number to 3 ?
someone can explain that to me please ?
 

Ian0

Joined Aug 7, 2020
2,196
I assume you have a motor with three or four wires to it - three lives and possibly a neutral, and you have measured the current in one of the live wires.
To calculate the total current you can measure the current in one live and multiply by three. (You should check that the current in the other two lives is about the same and the neutral current is about zero, if there is a neutral connection)
The total current is not a particularly useful number. It is less confusing if you quote it as "8 Amps per phase", then everyone knows what you mean.
If you need the VA then 8Amps x 3 x 230V (or whatever phase to neutral voltage you have) is the VA.
If you need the power consumption, the you also need the phase angle of the current - you will need a power analyser or a scope to measure that.
 

Thread Starter

dashhossein

Joined Jul 30, 2020
42
I assume you have a motor with three or four wires to it - three lives and possibly a neutral, and you have measured the current in one of the live wires.
To calculate the total current you can measure the current in one live and multiply by three. (You should check that the current in the other two lives is about the same and the neutral current is about zero, if there is a neutral connection)
The total current is not a particularly useful number. It is less confusing if you quote it as "8 Amps per phase", then everyone knows what you mean.
If you need the VA then 8Amps x 3 x 230V (or whatever phase to neutral voltage you have) is the VA.
If you need the power consumption, the you also need the phase angle of the current - you will need a power analyser or a scope to measure that.
I want to know how many watts of energy our three-phase motor consumes per second if the current in each phase wire is eight amps
 

Ian0

Joined Aug 7, 2020
2,196
There's no such thing as "Watts per second". Watts are Joules per second.
You need to know the power factor or the phase angle of the current in order to calculate the true power.
 
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