DFFHV11FW2637 datasheet(3/13 Pages) AVX

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Medium Power Film Capacitors

FFHV/FTHV 1500Vdc to 3000Vdc

HOW TO CHOSE THE RIGHT CAPACITOR

Time

1/f

The capacitor lifetime depends on the working voltage and the hot spot temperature.

Our caps are designed to meet 100000 hours lifetime at rated voltage and 70°C hot spot temperature. In accordance with

operating conditions, please calculate the hot spot temperature and deduce from this calculation if the obtained lifetime can suit

the application.

1. From the tables, select a capacitor with required capacitance

Cn and voltage Un.

Calculate the maximum ripple voltage allowed for the selected cap:

Urmax = 0.2Un

If Ur>Urmax, select a capacitor with higher rated voltage

Make sure Irms application < Irms table

Copy out:

• serial resistance (Rs): see table of values

• thermal resistances Rth1 and Rth2 (depending on cooling conditions)

2. Hot spot temperature calculation

Total losses are calculated as follow: Pt=Pj+Pd

Joule losses: Pj = Rs x Irms²

Dielectric losses: Pd = Q x tg

δ0 with

• Q(reactive power) = Irms2 for a sinusoidal waveform

–––––

• tg

δ0 = 2 x 10-4 (dielectric losses of polypropylene)

Hot spot temperature will be:

HS =

amb + (Pj + Pd) x (Rth1 + Rth2)

absolute maximum is 85°C

If temperature is higher than 85°C, come back to #1 and start again

with another selection.

Rth1: thermal resistance between hot spot and case

Rth2: thermal resistance between case and ambient air

3. Refer to the curve and deduce the lifetime vs Uw/Un ratio

width

CASE

AMB

Rth1

Rth2

eg: rated voltage 2000V

working voltage 1900V

ρ = 0.95 ⇒ lifetime 200,000 hours

@ 70°C hot spot temperature

Please, find a calculation form at the end of the catalog

1.5

1.4

1.3

1.2

1.1

0.9

0.8

0.7

100

1,000

10,000

100,000 200,000

0.95

1,000,000

Lifetime Expectancy (hours)

θHS = 65ºC

DFFHV11FW2637 Datasheet(PDF) 3 Page - AVX Corporation

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