Voltage Drop Calculation for Star Delta Starter Motor

Calculate for one cable and half it.

Yes. British Standard 7671 contains it.

Dear PWSlack,

Thank you for your reply, can u please let me know the section in BS 7671.

Yes. It can be found using the index at the front of the standard.

More precisely stated, the methods above will give you the voltage at the motor terminals when starting in Star, knowing the length (150 meters given) and the cross sectional area and construction of your motor feeder conductors.

I can understand your concern, 150 meters is a long distance for motor conductors, and will require up-sizing for voltage drop, over and above the motor running load rating. The use of a star-delta motor starter already reduces the accelerating torque available for your load, long leads makes it even worse. If your power system is stiff enough to reduce flicker at start to acceptable levels, across-the-line starting will produce better results with less investment and complexity, being more reliable with reduced parts count. Reduced voltage starters stress the rotor windings of your typical induction motor, as time below design slip frequency translates to heat in the rotor windings, i.e. a 50Hz frequency applied to a rotor turning zero to 90% rated rpm. Lower available accelerating torque (voltage) increases the accelerating time, adding even more heat to the motor rotor.

V_drop = IR

? why don't you just measure it?