[s]

Hi

 

Static or rotating device : this is a mechanical difference (even for AC inductive motors which have electrical rotating magnetic flux)

But the general rule is : as long as there is inductance (or capacitor) inside the load, their is an apparent power and reactive power,

Please note that reactive power is the power responsible of creating the magnetic flux (which is 90% of cases apply on rotating machines :)

 

To know the apparent and reactive power on any machine, I'll use an inductive motor as an example,

On every motor there is a name plate, which must indicates the apperant power (  Pn in W or KW or HP ) , Voltage ( in V ), and the phase shift ( cos phy ), and nominal current ( In in A)

Those values are for the full load,

for lower loads you should measure the current I and compare it to the nominal current In and devide with the calculated ration I/In=A

P =Pn x A, Q=Qn x A

Now for Q reactive power in VAR 

Q=P x tg (Phy)

Phy can be known by any scientefic calculator,

 

Please note that the Harmonics effects are not considered here.

 

Take care

[s]

Hi

 

Is this problem has arosen recently?

Or is it a factory default?

[s]

Hi 

 

The electrical current has 2 main effects : thermal effect and electromagnetic effect.

 

The non-bursting current is the maximum current that the cable can carry without causing the bursting of the sheath ( cable isolator) caused by electromagnetic forces,

Commonly those forces are neglected and only the thermal effect of the current is considered,

But for larger currents the electromagnetic forces are considerable and taking them into consideration during the calculation sometimes causes a lower cable's short circuit current rating .

 

Please note that many respected cable manufacturers provide the maximum non-bursting current value.

 

Hope that those info are useful for you,

 

Take care

 

Nael Samman 

[Author]

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