Current Capacity of Some Equipment

·         1 Phase Motor draws Current = 7Amp per HP.

·         3 Phase Motor draws Current = 1.25Amp per HP.

·         Full Load Current of 3 Phase Motor = HPx1.5

·         Full Load Current of 1 Phase Motor = HPx6

·         No Load Current of 3 Phase Motor = 30% of FLC

·         KW Rating of Motor = HPx0.75

·         Full Load Current of equipment = 1.39xKVA (for 3 Phase 415Volt)

·         Full Load Current of equipment = 1.74xKw (for 3 Phase 415Volt)

Power Cables

Cable Capacity

1.     For Cu Wire Current Capacity (Up to 30 Sq.mm) = 6X Size of Wire in Sq.mm. Ex. ...

2.     For Cable Current Capacity = 4X Size of Cable in Sq.mm, Ex. For 2.5 Sq.mm = 4×2.5 = 9 Amp.

3.     Nomenclature for cable Rating = Uo/U.

4.     where Uo = Phase-Ground Voltage, U = Phase-Phase Voltage, Um = Highest Permissible Voltage.

 

 

Minimum Bending Radius

·         Minimum Bending Radius for LT Power Cable = 12 x Dia of Cable.

·         Minimum Bending Radius for HT Power Cable = 20 x Dia of Cable.

·         Minimum Bending Radius for Control Cable = 10 x Dia of Cable.

Power Transformer

Transformer

·         Current Rating of Transformer = KVA x 1.4

·         Short Circuit Current of T.C /Generator = Current Rating / % Impedance

·         No Load Current of Transformer =< 2% of Transformer Rated current

·         Capacitor Current (Ic) = KVAR / 1.732xVolt (Phase-Phase)

·         Typically the local utility provides transformers rated up to 500kVA for maximum connected load   of 99kW,

·         Typically the local utility provides transformers rated up to 1250kVA for maximum connected load   of 150kW.

·         The diversity they would apply to apartments is around 60%

·         Maximum HT (11kV) connected load will be around 4.5 MVA per circuit.

·         4No. earth pits per transformer (2No. for body and 2No.for neutral earthing),

·         Clearances, approx.1000mm around TC allow for transformer movement for replacement.