Formula For Capacitance

Capacitors connected in series

• Total capacitance will = the sum of the reciprocals

• Total voltage rating = sum of the capacitor voltage ratings
  
  

Capacitors connected in parallel

• Total capacitance = the sum of the individual capacitors

• Total voltage rating = voltage of the lowest rated capacitor
  
  

Practice exercise for capacitors

1. Two Capacitors connected in series

#1 120mfd 120volts
#2 65mfd 230Volts

Find total allowable voltage applied and total MFD rating of capacitors

 

ET = E1 + E2

ET = 120v + 230V

ET = 350V

1/CT = (1 + 1) / (C1 + C2)

1/CT = (1 + 1) / (120 + 65)

CT= 1/ (2 / 185)

CT = 42.16mfd

2. Three Capacitors connected in parallel
#1 25mfd 330 volts
#2 5mfd 220 volts
#3 10mfd 550 volts

Find total allowable voltage and total Mfd of capacitors?

Et = E1 = E2 or lowest

Et = 220V

Ct = C1 + C2 + C3

Ct= 25 + 5 + 10

CT = 40mfd

3.Four capacitors connected in series all with the same rating of 15 Mfd. But each has a different voltage rating as following #1 220V #2 440Volts #3 550V #4 360V. Find the total capacitance as well as the total allowable applied voltage

Et = E1 + E2 + E3 + E4

Et = 220 + 440 + 550V + 360

Et = 1570V



1/CT = (1/C1) + (1/C2) + (1/C3)+ (1/C4)

CT = 1/ (1/15) + (1/15) + (1/15)+ (1/15)

CT = 3.75 mfd