Basic Power related formulas

Below are very basic Power related formulas which is used in designing of electrical systems.

1. Connected Load :

Connected Load is the sum of power capacity of all the loads. It is rated in KW or KVA

Connected Load (in KVA) = Load 1 (in KVA) + Load 1 (in KVA)

Connected Load (in KW)  = Load 1 (in KW) + Load 1 (in KW)

2. Power

Signe Phase Power Formula:

P (VA) = V x I

P (KVA) = (V x I) / 1000

P (W) = V x I x Cos Ჶ

P (KW) = V x I X Cos Ჶ / 1000

Three Phase Power Formula:

P (VA) = √3. V x I

P (kVA) = (√3. V x I) /1000

P (W) = √3. V x I x Cos Ჶ

P (KW) = √3. V x I x Cos Ჶ / 1000

3. Demand Factor

It is the ratio of Maximum Demand to total connected load. 

Demand Factor = Maximum Demand / Total connected Load

It is always less than one. 

It should be applied to group loads

4. Load Factor 

It is the ratio of Average Power consumed to its peak power. 

Load Factor = Average Power / Peak Power

If the load factor is 1 or 100%. It is good for the system. If it is less than 1 or 100%, it may be caused due to switching or starting of that appliance.

5. Diversity Factor 

It is the ratio of Sum of Maximum Power Demand to maximum Demand. 

Diversity Factor = Sum of maximum Power Demand / Maximum Demand

It is always >1

Diversity Factor should be considered for individual load

6. Plant Factor = Average Load / Capacity of the plant

7. Conversions

1 HP = 0.746 KW

1 KW = 1.341 HP

If you consider 0.8 as power factor, 

From the power formula, P (KW) = (√3. V x I /1000) x Cos Ჶ

                                         P (KW) = P (KVA) Cos Ჶ

                                         P (KW) = P (KVA) x 0.8

Where Cos Ჶ is power factor 

i) KW = 0.8 x KVA

ii) KVA = 1.25 x KW

iii) HP = 0.933 KVA