Joule Effect Calculation

[yulinios]

Hi There!

I would like to know how calculate Joule Effect losses in a 48.2 MVA Generator when its temperature increase in 3°C, working at same base load 43.5 MW, working at pf of 1.00.

How can I find "R"? in I^2 X R.

 

[waross]

Hello yulinios
This sounds like a thermodynamics problem more than an electrical problem. If you know the losses and the ambient temperature you may be able to get an estimate by considering the change in the temperature rise. Eg; 30 degree temperature rise to 33 degree temperature rise = +10%.
This simple calculation will probably be inacurrate because of cooling air removing an unknown amount of heat from internal masses of unknown temperature.
R in I^2R, Look in the literature and specifications of the unit in question.
43.5 MW sounds a little high for a 48.2 MVA set. What is the rated Power Factor?
yours

 

[yulinios]

Waross

Power Factor rated is 0.9, I don't know the losses in the Generator, I would like to calculate losses in generator when the temperature increase from 83°C to 86 °C.

Bye There

 

[waross]

Why has the temperature increased? Has the ambient temperature risen or has the currrent through the generator increased?
If the ambient temperature has risen, most of the losses may stay the same. The I^2R losses will increase by a small amount. This will be based on the change in resistance of the windings with a 3 degree temperature difference.
Eddy current losses will decrease a small amount.
insulation resistance losses will vary as the insulation resistance varies.
Perhaps someone else knows if hysterisis losses are temperature dependant.
As far as the total losses, there is not enough information to even consider calculating losses.
There are many members who will be able to estimate the losses base on first hand experience.
yours

 

[yulinios]

Thanks Waross

The generator is almost new 1 year in operation, it has been left with a cooling water flow of 40 l/s (15°C inlet), the manufacter manual of coolers says 30 l/s (25°C inlet), the problem for the tube coolers is the velocity greater than 2 m/s (reached with flows > 30 l/s) and the water used is a river water in a open cooling water circuit. When we reduce the flow to rated flow, from 40 to 30 l/s the winding temperature increase from 83 to 86 °C, we would like to know the losses in kW because with this reduce of flow are saving energy in pumping and care tube coolers.

Bye There.

 

[waross]

Can the coolers be split into two circuits which are then put in parallel? That would probably solve your cooling problem and velocity problem at the same time.
My concern with the temperature rise is not the energy but the effect on the life of the insulation.
What is your energy source? Do you see a noticable difference in fuel consumption?
Does your manufacturers literature give the copper loss? If you calculate the ratio of the resistance of copper at 83 degrees to the resistance of copper at 86 degrees, you will have the ratio of the increase of the copper losses. I^2 stays the same but R goes up a little.
I am sorry but I don't know how hysteresis losses respond to an increase in temperature. I would expect the eddy current losses to be slightly less but not much. Again dependant on the resistance increase with a slight rise in temperature.
Let's see if someone else can help with this.
respectfully