I am posting this under threat of being dragged off to a gulag somewhere in the far-flung corners of Siberia!

A final circuit is to be installed to supply a 400V three-phase 28Kw motor for a conveyor system. The motor has a power factor of 0.85.

The circuit is 36m long and is to be installed using four-core armoured 90°C thermosetting insulated cable with copper conductors. One of the cores of the cable will be used as the cpc.

The cable is to be supported on a horizontal perforated cable tray in an ambient temperature of 38°C and touching one other similar circuit which has a conductor operating temperature of 70°C. The circuit is to be connected to a switchfuse at the installation origin. Circuit protection is to be provided by BS88-2gG fuses. Voltage drop for this circuit must not exceed 6v

The installation forms part of a 400/230v TPN TN-C-S system with an external earth fault loop impedance and measured and recorded as 0.05Ω.

Show all calculations.

Determine for the final circuit the

1. Design current (3 marks)

1. Rating of protective device (In) (1 mark)

1. Method of installation reference (2marks)

1. Rating factors that apply (4 marks)

1. Table number and column used to select current carrying capacity within BS 7671 (2 marks)

1. Minimum size of live conductors for current carrying capacity and voltage drop (5 marks)

1. Actual voltage drop (3 marks)