PTC thermistors for overcurrent protection and as inrush current limiters

Leaded disks, 260 V up to 1000 V

B597**C0*/ B594**C1*

PPD PTC PD

2022-01-28

Please read Cautions and warnings and

Page 5 of 23

Important notes at the end of this document.

Calculation of the number of required PTC elements

Number of required PTC elements (connected in parallel) as function of capacitance and charging

voltage of smoothing or DC link capacitor:

K

K factor

K = 1 for DC source

K = 0.96 for 3-phase bridge rectifier

K = 0.76 for single phase bridge rectifier

N

Number of required PTC thermistors connected in parallel

C

Capacitance of smoothing or DC link capacitor in F

V

Charging voltage of capacitor in V

Cth

Heat capacity in J/K

Tref

Reference temperature of PTC in °C

TA,max Expected maximum ambient temperature in °C

In case of large N values the resulting resistance of the parallel PTC network might be too low for

effective limitation of the charging current. In this case a combination of series and parallel connected

PTC thermistors can be used.