Power Factor

I'm waiting to hear about some large capacitive process that needs power factor correction inductors....

You can be penalised by your supply company for over correction as well as under correction. It's up to you to set it up right.

The reason for the penalty on some tariffs is that it costs the power company more money to send low-power-factor power to the user in terms of cable losses per kWh supplied, and the penalty is there to discourage the user from presenting low power factor loads to it, thereby protecting the power company from incurring unrecoverable costs.

The over-connected PFC (Power factor Compensation) is same as under-connected PFC (with a few additional)

- The Active power demanded by load is constant.

- reactive power - ditto - only that a part (or full or more than full) is supplied through PFC.

- Between the meter (for whose reading you pay) and the Load there is the PFC (and it may be any where - near load, near meter, in between)

- Between the PFC and Load - the current can not be tweaked with (it is the load demand)

- The current only varies between the meter and PFC.

- The active part of this current is not in user's control per se (except changing the load, which may be considered impractical).

- The total current (active + reactive) will create the losses in this segment

= I²R = I_a²R/pf² (I_a = Active current, R = Line resistance for this segment)

- The Power factor whether + or - makes the same sense hence, (Though it must be noted that though the expression looks intimidating, actually in a properly designed system R is so low that the calculated value doesn't)

In addition to the above

- Over designed PFC = extra capacitors and the relevant circuits

- More parasitic losses (they do exist)

The optimum designed PFC would be (assuming it is APFC (automatic) - sufficient to take care of normal worst power factor condition, including near future expansions.

- provided the parasitic losses of the PFC more than compensates for the losses (penalties for poor power factor, line losses and the cost of the PFC)

Thanks.

So it is important to correctly size and configure the capacitor.

It is important for an appropriately-qualified Electrical Engineer to select power factor correction equipment that will achieve an economic level of power factor correction, and to ensure that the equipment is correctly selected, installed, operated and maintained.

Now there are APFC panels, why don't you try them out?

They will take care of variable pf demands.

But still, your statement stands.

Yes, Over correction of power factor will in crease the bus voltage, which means motors get over excite and which cause them to use more energy which will lost in the form of heat.

This increase in current will cost to the industrial customer and this increased cost is passed on to the customer.

Power utilities can and do charge a penalty for leading power factor as well as lagging.

Vinu_Answers Sure_Answers