Suppression Chokes

Chokes

All SCHURTER filters are fitted with chokes that satisfy the guidelines set down by international and national standards organizations.

The most important test data for RF suppression chokes are:

Maximum variation

of –30% / +50% for compensated

inductance: –15% / +15% for linear and storage

Testfrequency 1MHz ± 20% at L 10 μH

 100kHz ± 20% at 10 μH < L 1 mH

 10kHz ± 20% at 1 mH < L 50 mH

 50 to 120 Hz ± 20% at L > 50 mH

Test current: 0.1 mA

Testtemperature: 25°C ± 3°C

Insulation resistance Ris: 6000 MΩ

Test voltages according to IEC 60938-2

The main type of choke used in suppression filter engineering is the current compensated choke. This mainly damps the common mode interference. The differential mode parasitic current, or rather the magnetic flux they produce in the core, is compensated by means of a special type of winding. The relatively small attenuation of the differential mode parasitic currents can be balanced through the large, symmetrically connected capacitance Cx between the lines. Only the leakage inductance Ls of the choke is then of any importance.

The high nominal inductance LN active for common mode parasitic currents allows the insertion of small, earthed capacitances CY in a filter circuit. These capacitances are regulated by international standards for leakage currents.

All SCHURTER filters are fitted with class X or Y RF suppression capacitors in accordance with international standards (IEC, EN). These are mainly self-healing metallized paper, polyester or polypropylene types, tested against the standards of major countries around the world and approved as noise suppression capacitors. Class X capacitors are capacitors with unlimited capacity for those applications in which a failure caused by a short circuit cannot result in a dangerous electrical shock. Class Y capacitors are capacitors intended for an operating voltage Ueff = 250 V with increased electrical and mechanical safety and limited capacitance.

All SCHURTER filters are equipped with components which have been tested and approved as RF suppression capacitors.

The most important test data for RF suppression capacitors are:

Capacitance Cx, Cy ± 20% for fM = 1 kHz

Insulation resistance Ris between the capacitor terminals:

for C > 0.33 μF: Ris x C > 2000 s (time constant)

for C 0.33 μF: Ris > 6000 MOhm

Major voltage test and standards for CX and CY capacitors