Document Number: 26013

For technical questions, contact: dc-film@vishay.com

www.vishay.com

Revision: 06-Oct-08

8

MKT 1813

Metallized Polyester Film Capacitor

MKT Axial Type

Vishay BCcomponents

POWER DISSIPATION AND MAXIMUM COMPONENT TEMPERATURE RISE

The power dissipation must be limited in order not to exceed the maximum allowed component temperature rise as a function of

the free ambient temperature.

The power dissipation can be calculated according type detail specification “HQN-384-01/101: Technical Information Film

Capacitors”.

The component temperature rise (

ΔT) can be measured (see section “Measuring the component temperature” for more details)

or calculated by

ΔT = P/G:

•ΔT = Component temperature rise (°C)

• P = Power dissipation of the component (mW)

• G = Heat conductivity of the component (mW/°C)

MEASURING THE COMPONENT TEMPERATURE

A thermocouple must be attached to the capacitor body as in:

The temperature rise is given by

ΔT = T

To avoid radiation or convection, the capacitor should be tested in a wind-free box.

APPLICATION NOTE AND LIMITING CONDITIONS

These capacitors are not suitable for mains applications as across-the-line capacitors without additional protection, as described

hereunder. These mains applications are strictly regulated in safety standards and therefore electromagnetic interference

suppression capacitors conforming the standards must be used.

To select the capacitor for a certain application, the following conditions must be checked:

3. The voltage peak slope (dU/dt) shall not exceed the rated voltage pulse slope in an RC-circuit at rated voltage and without

divided by the applied voltage.

For all other pulses following equation must be fulfilled:

T is the pulse duration

The rated voltage pulse slope is valid for ambient temperatures up to 85 °C. For higher temperatures a derating factor of 3 %

per K shall be applied.

4. The maximum component surface temperature rise must be lower than the limits (see figure max. allowed component

temperature rise).

Thermocouple

2

dU

dt

--------

⎝⎠

⎛⎞

2

0

T

∫

dt

U

Rdc

dU

dt

--------

⎝⎠

⎛⎞

rated

×

<

×

×