Summary Energy formulas

SUBJECT: ENERGY FORMULAS for CEA and CEM


File name: Formula sheet for CEA and CEM Rev 1 Revision: 0



Basic Electricity
Symbol Description SI Units
P Power Watt (W)
V Voltage Volt (V)
I Current Amp (A)
R Resistance Ohm (Ω)
PF Power Factor %
Eff Efficiency %
HP Horse Power HP
KVA Kilo Volt Amps KVA
KWH Energy Consumption kWh

V × Eff × PF
P = 1000

V×I
KVA = 1000 Only to be used with single phase
values
V × I × Eff × PF
HP = 746

Hp × 746 P × 1000 KVA × 1000
I= = V × Eff × PF =
V × Eff × PF V



1.73 × V × Eff × PF
P = 1000

1.73 × V × I
KVA = Only to be used with 3 phase
1000
values
1.73 × V × I × Eff × PF
HP = 746

Hp × 746 P × 1000 KVA × 1000
I = 1.73 × V × Eff × PF = 1.73 × V × Eff × PF = 1.73 × V

kW
PF = kVA = Cos Ө

𝐾𝑊𝐻 𝑢𝑠𝑒 𝑖𝑛 𝑎 𝑃𝑒𝑟𝑖𝑜𝑑
𝐿𝑜𝑎𝑑 𝐹𝑎𝑐𝑡𝑜𝑟 =
𝑃𝑒𝑎𝑘 𝐾𝑊 × 24 × 𝑁𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑑𝑎𝑦𝑠 𝑖𝑛 𝑡ℎ𝑒 𝑃𝑒𝑟𝑖𝑜𝑑

The load factor is an indicator of how steady an electrical load is over time
High load factor = efficient plant

, Electricity Motors
Symbol Description SI Units
P Power Watt (W)
V Voltage Volt (V)
I Current Amp (A)
LF Load Factor kW
SS Shaft Speed RPM
F Frequency Hz
NL No Load
FL Full Load
S Speed RPM
PS Power Savings motor kW
T Time Hours
ƞ Efficiency %
Full load = VxAxPFx√3

𝐹 × 60
Shaft Speed = Synchronous Speed = 𝑁𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑃𝑜𝑙𝑒𝑠 For no load (NL)
Conditions only
𝑁𝐿 𝑆𝑝𝑒𝑒𝑑−𝑀𝑒𝑎𝑠𝑢𝑟𝑒𝑑 𝑆𝑝𝑒𝑒𝑑 𝑇𝑟𝑢𝑒 𝑆𝑙𝑖𝑝
%Motor Load = = 𝐷𝑒𝑠𝑖𝑔𝑛 𝑆𝑙𝑖𝑝
𝑁𝐿 𝑆𝑝𝑒𝑒𝑑−𝐹𝐿 𝑆𝑝𝑒𝑒𝑑



𝑘𝑊 𝑛𝑎𝑚𝑒 𝑝𝑙𝑎𝑡𝑒 × 𝐿𝐹 𝑘𝑊 𝑛𝑎𝑚𝑒 𝑝𝑙𝑎𝑡𝑒 × 𝐿𝐹
Power Saving motor = old - new
ƞ ƞ


This formula compares old electrical motors with new, more efficient electrical motors.
The power saving is in kW
Ƞ = Fracture (% divided by 100)

Power saving consumption = Power Saving motor x Time


Design Slip = NL Speed – FL Speed


True Slip = NL Speed – Measured Speed

100 100
Annual Saving = kW Name Plate x LF x Cost/kW x Hours / year x [%ƞ𝑂𝑙𝑑 − %ƞNew]