Interference Capacitor

[GBDamo]

Doing a favour for the bosses dad this morning.

He has a Bosch cooker good that's tripping his RCD. For some unknown reason his kitchen fitters have cut tiles around the hood rather than take it off, tile and refit. He's now selling the house and doesn't want to re-tile so is happy to spend a little on a ten year old hood rather than replace.

The problem is there was an Interference Capacitor in the mains terminatiin box. The capacitor has three wires L, N and E which were in the mains connector block alongside the mains. So this was not in line but sat on the mains conductors.

The OEM cap had blown and been replaced with one supplied by a high street retailer. The old cap has been binned so I cannot compare the two.

I do not know the exact specs of the OEM cap so have to assume the replacement is correct.

I have contacted Bosch but they do not keep technical specifications for discontinued items.

The image is identical except the 0.0027uf rating on the replacement cap is 0.005.

The circuit and RCD test fine.

Does anybody know what the purpose of this component is, how to test if it is faulty?

I have tested both L and N to the earth wire and both have approx 2MOhms resistance at 250V.

TLR

What the hell's an interference capacitor.
[automerge]1595263871[/automerge]

Doing a favour for the bosses dad this morning.

He has a Bosch cooker good that's tripping his RCD. For some unknown reason his kitchen fitters have cut tiles around the hood rather than take it off, tile and refit. He's now selling the house and doesn't want to re-tile so is happy to spend a little on a ten year old hood rather than replace.

The problem is there was an Interference Capacitor in the mains terminatiin box. The capacitor has three wires L, N and E which were in the mains connector block alongside the mains. So this was not in line but sat on the mains conductors.

The OEM cap had blown and been replaced with one supplied by a high street retailer. The old cap has been binned so I cannot compare the two.

I do not know the exact specs of the OEM cap so have to assume the replacement is correct.

I have contacted Bosch but they do not keep technical specifications for discontinued items.

The image is identical except the 0.0027uf rating on the replacement cap is 0.005.

The circuit and RCD test fine.

Does anybody know what the purpose of this component is, how to test if it is faulty?

I have tested both L and N to the earth wire and both have approx 2MOhms resistance at 250V.

TLR

What the hell's an interference capacitor.

Image and some words

 

[DPG]

Bear in mind capacitors have to x or y rated depending if they are connected between live/earth or live/neutral.

 

[GBDamo]

Bear in mind capacitors have to x or y rated depending if they are connected between live/earth or live/neutral.

This one piggybacks on all three my guess is it's an over voltage filter that leaks excess voltages to earth.

 

[telectrix]

it's just an interference suppressor. without it he may get some radio or TV. interference when the motor is running. when i find a blown one, i just bin it.

 

[GBDamo]

it's just an interference suppressor. without it he may get some radio or TV. interference when the motor is running. when i find a blown one, i just bin it.

As the name say

Cheers Tel, the old boy can live with that.

 

[Lucien Nunes]

Better terms would be 'interference suppressor capacitor' or 'delta capacitor', rather than 'interference capacitor'. Its purpose is to prevent the supply cable acting as an aerial and emitting radio-frequency interference that is generated within the appliance. Many white goods and almost every appliance with a brush motor has one. They are often used with or combined with inline chokes.

It's actually three capacitors in a delta formation; two small ones L-E and N-E and a larger one L-N. They are used in both class I and II appliances; in the latter the E terminal connects to the main metal chassis or motor frame etc. The capacitance of each section is chosen such that it does not pass significant current at 50Hz, but up in the MHz range the reactance is low enough to bypass RF currents that would otherwise produce a voltage between the conductors. The L-E and N-E sections are Y-rated, which are supposed to fail safe / open / low capacitance rather than leaky / short. Their maximum permitted capacitance is limited by the leakage current they produce.

Removing a delta cap will not affect the function of an appliance, but could affect the reception of nearby TV/Radio/other RF devices, although the most troublesome combination of AM radio and brush motor is not so common these days.

 

[GBDamo]

Better terms would be 'interference suppressor capacitor' or 'delta capacitor', rather than 'interference capacitor'. Its purpose is to prevent the supply cable acting as an aerial and emitting radio-frequency interference that is generated within the appliance. Many white goods and almost every appliance with a brush motor has one. They are often used with or combined with inline chokes.

It's actually three capacitors in a delta formation; two small ones L-E and N-E and a larger one L-N. They are used in both class I and II appliances; in the latter the E terminal connects to the main metal chassis or motor frame etc. The capacitance of each section is chosen such that it does not pass significant current at 50Hz, but up in the MHz range the reactance is low enough to bypass RF currents that would otherwise produce a voltage between the conductors. The L-E and N-E sections are Y-rated, which are supposed to fail safe / open / low capacitance rather than leaky / short. Their maximum permitted capacitance is limited by the leakage current they produce.

Removing a delta cap will not affect the function of an appliance, but could affect the reception of nearby TV/Radio/other RF devices, although the most troublesome combination of AM radio and brush motor is not so common these days.

Thanks Lucien, (a lot.....words)