Electrical Basic Concepts
Understanding basic electrical concepts is crucial for electrical engineers and professionals. Here are some essential electrical formulas, commonly known as electrical thumb rules:
1) Current Taken by Motor in Amps: KW x 1.73
To determine the current drawn by a motor, multiply its power in kilowatts by 1.73.
2) Current Taken by Motor in Amps: HP x 1.5
For motors specified in horsepower, multiply the power rating by 1.5 to calculate the current.
3) Current Capacity of DG Set in Amps: KVA x 1.39
To find the current capacity of a diesel generator (DG) set, multiply its apparent power rating in kilovolt-amps (KVA) by 1.39.
4) Current Capacity of Transformer in Amps: KVA x 1.39
For transformers, the current capacity is determined by multiplying the apparent power rating in KVA by 1.39.
5) Starting Current of Motors using DOL Starter: Rated Current x 6
When using a direct-on-line (DOL) starter, estimate the starting current by multiplying the rated current of the motor by 6.
6) Starting Current of Motors using Star Delta Starter: Rated Current x 3
For motors connected using a star-delta starter, the starting current is approximately three times the rated current.
7) Starting Current of Motors using Soft Starter: Rated Current x 3
When employing a soft starter, multiply the rated current of the motor by 3 to obtain the starting current estimation.
8) Starting Current of Motors using VFD Starter: Rated Current x 1.5
For motors utilizing a variable frequency drive (VFD) starter, the starting current is around 1.5 times the rated current.
9) Instantaneous Peak Current Carrying Capacity of Transformers: Rated Current x 1.5
To determine the instantaneous peak current carrying capacity of transformers, multiply the rated current by 1.5.
10) Instantaneous Peak Current Carrying Capacity of DG Sets: Rated Current x 1.5
For DG sets, the instantaneous peak current carrying capacity can be estimated by multiplying the rated current by 1.5.
11) Derating Factor of Cable Current Capacity in Air: 0.6
To account for cable installations in open air, apply a derating factor of 0.6 to the cable's current capacity.
By familiarizing yourself with these electrical concepts and formulas, you can make accurate calculations and ensure the efficient functioning of electrical systems.