Star Delta Calculation

Hello Electrical Gurus

I have a question about star delta calculation. I will try and write all the information I have related to my question along with my calculations. But before I proceed I will like to make it clear that I will not be doing any installation or designing and this is just primarily for my own understanding.

Main Supply Voltage = 400V/3Phase/50Hz

Motor Power = 18.5KW (Condenser Pump) (Continuous Duty)

Ambient Temperature = 40C

Starting Method = Star Delta

Cable Installation Method = Conduit

Distance from the panel to starter = 1meter

Distance from the starter to motor = 20meter

I want to calculate the following,

a. MCCB

b. Cable size from main supply panel to starter and from starter to motor

c. Size of Main contactor, Delta Contactor and Star Contactor

d. Size of overload

My calculation

Full Load Current = 18.5KW/1.732*400*0.85*0.94 (0.85 = p.f and 0.94 = efficiency)

FLC = 33.42A (FLC I have obtained from ABB Motor Catalogue is 34A)

MCCB = 1.5*FLC = 1.5*33.42A = 50.13A

(I am confused on how to select the best MCCB rating. I mean like NEC states, if I am right to select MCCB at 2.5*FLC. What about IEC or BS7671?) I am trying to follow the BS7671

Cable size

From Panel to starter.

Cable size = 16mm (Table 4D2A 16mm cable ampere rating = 62A)

Applying derating factor at 40C we have 62*0.87 = 53.94A This is sufficient in my opinion. Keeping in mind I have a 50A MCCB installed.

Voltage drop

Starting current in star delta = 3*FLC = 3*33.42 = 100.26

Vd (Running) = 2.4*1*33.42/1000 = 0.08V (OK)

Vd (Starting) = 2.4*1*100.26/1000 = 0.24V (OK)

Cable Size from starter to motor

I will have 6 cables going from the starter to motor. Each set of cable need to be rated at 58% of the FLC. Therefore

Cable size = 0.58*33.42 = 19.38A ( From table 4D2A I have selected 4mm which has a 27A rated capacity)

Applying derating factor at 40C = 23.49A which is good

Voltage drop

Vd = 9.5*20*33.42/1000=3.68V (Which is good)

Main Contactor = 0.58*FLC = 0.58*33.42 = 19.38

Delta contactor = 0.58*FLC = 0.58*33.42 = 19.38

Star Contactor = 0.33*FLC = 0.33*33.42 = 11.02A

Overload = 0.58*FLC = 0.58*33.42 = 19.38A

I know there are a lot of calculations but can someone check them for me. Are they right? If not can you please highlight my mistakes and if its totally wrong can you please explain the calculation or point me to a good literature.

Many thanks

Regards,