Hello everyone.Today, almost every normal household appliance has special filters installed that do not pass interference signals from the 220 Volt network to the device or back from the equipment to the network.Such filters are available in televisions, monitors, washing machines and other appliances and such filters are installed where the plug is connected to the 220 Volt socket of the device.I got such a filter from a washing machine, its name is AERODEV DNF06-T.There is information on the filter housing that the current that can pass through the filter is 16 amperes at a mains voltage of 250 Volts.
The filter scheme and the nominal values of the parts are also indicated.This is one capacitor X with a capacity of 1 UF, two capacitors Y with a capacity of 22 nF each and a common-mode choke, which contains two windings with an inductance of 1 mH each.A resistor with a resistance of 470 kOhm serves to discharge the capacitor X.
How does such a filter work? A common-mode choke is installed at the filter input, which dampens common-mode interference (bad signal) and the useful signal-differential passes.These common-mode interference can occur in household appliances during switching of field-effect power transistors, etc. and there is interference on two power wires at once.The two windings of the common-mode choke are wound in such a way that the magnetic fields of interference coming along the two wires add up and extinguish each other.Moreover, the winding step of the throttle windings should be the same and the number of turns should also be the same.
When there are two signals with the same half-wave at the input of the two windings of the throttle, and this is a common-mode signal, the throttle windings will increase their inductance to the maximum and at the output of the windings the amplitude of common-mode interference will be minimal.The differential signal passes through the throttle with the least loss.
the common-mode choke is made on a ring.
The number of turns of each choke winding is 11 with a wire of approximately 1.2 mm diameter.I checked the inductance of one winding with a tester and it is 1.8 mH, which is higher than what is indicated on the case.
The throttle is wound on a ferrite ring with a diameter of approximately 25 mm.
Other filter components are capacitors X and Y.Why are they so called and what function do they perform in the filter?
X capacitor usually has a larger capacity than Y capacitors.The X capacitor is used to suppress antiphase interference that can be in the 220 Volt network or come into the network from the device.It is installed on the power supply between phase and zero.This capacitor must withstand short-term emissions of interference, which have a large voltage amplitude.Also do not support gorenje and on their body there is an inscription X.
Capacitors Y are connected in series.The two extreme terminals of the two capacitors are connected between phase and zero, and the connection of these two capacitors is connected to ground.These capacitors, as well as X, suppress common-mode interference and also divert a high-voltage interference pulse to the ground.There is a letter Y on the housings of such capacitors, and the connection terminal of these two capacitors is connected to the housing of household appliances.
If your household appliances are not grounded, then take a voltmeter and check the voltage on the device body and grounding, you will see that the voltmeter will show approximately 110 volts of voltage, although the current will be very small.This is exactly the work of Y-capacitors without grounding.Be sure to ground household appliances!
