How do I test how "dirty" my mains supply is?

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A friend of mine has just moved into a "barn conversion" and his hi-fi keeps tripping occassionally...
The hifi can;t be taken back to the dealer - as the dealer is in Saudi Arabia - but it is a 230/240v system and has worked perfectly well in the UK since being taken back
How do I help him eliminate that the mains supply culd be the problem
He has a huge f**k off fridge that I assume will dump loads of crap into the mains

Is there a way of testing how clean the Mains is using simple equipment?
 
Many thanks...
Pardon me for being thick but is that a leak to ground in the Hifi or in the mains?
 
The Hfi works by comparing (quite precisely) the current that goes into the consuming circuit, with the current returning from this.

If all is well, every uA of current supplied to the consuming circuits should return from that as well.

But if any of the current goes somewhere else (to ground), the in&out-currents will be different, and the Hfi trips (I think there's a standard 5mA threshold)

So if the relay trips, then in- and outgoing currents are not the same in your consuming circuits - and you must have a leak to ground...

Jakob E.
 
someone helped me out once by putting very large caps parallel on my mains close to my studio. The clicks and interference coming from the fridge stopped right after. We had te replace these caps a few times unfortunately. We were also very close to a large factory and when the evening shift ended we sometimes got a raise in voltage coming in (+/-40 to 60 V!), the caps didn't work for that btw, it sometimes disappeared after 15 minutes, i've been told that this was because of motors spinning out and feeding back power into the mains?

Anyway, caps are your friend :green:

Tony
 
Yes, caps may remove some noise - but they'll also cost you quite some power that will be lost as heat..

The simplest way to remove line noise is to get hold on one of these big mains filters that are found in the bottom of old heavy-computer gear at the scrap-yard. Look right after the power inlet.

Jakob E.
 
I believe the only power you'll lose as heat will be related to the ESR of the caps...? In one of my texts it talks about how you can put a cap across mains and it won't use a lick of power, it'll charge on the upcycle and discharge back into the grid on the downcycle. I assume they're talking about ideal capacitors, and the ESR would cause it to dissipate some power as heat.
 
Nope, any capacitor will short AC.

Depending, off course, on capacitance and frequency. This is how the noise-removal works; more "shorting" at higher frequencies...

Jakob E.
 
ok, now you've done it.

When I get home I'm gonna look that up and post what it says! :)

Sorry, but I trust Horowitz and Hill authoritatively on this stuff ;)
 
Hfi? is that like a GFI here in the states? Ground fault interrupter? most of these are electronic now but used to be thermal Bi-metal strips, is the one your friend has old or new? Here at my job we use GFIs in mobile units that run all kinds of motor drivers and inductive loads like motors, lights and compressors. These kick the GFI all the time. also, i don't know Euro wiring codes but here we usually wire neutral and ground together in the breaker box itself. it's at this point that an inductive load can capacitively induce a teeny tiny current flow for a microsecond that will trip the GFI. the gfi is based around two transformers also, usually built as multiple windings around the SAME ferrite core. inductive loads can also cause this winding to induce current flow falsely (like an electromagnet) if there are loads reaching the peak rating for the mains. it's really just false triggering because GFIs were never designed to see some of the things we hook up to them. it might be easiest to move the fridge to a dedicated circuit without a GFI/HFI.


:guinness:
 
[quote author="Svart"]it might be easiest to move the fridge to a dedicated circuit without a GFI/HFI.[/quote]
That sounds illegal to me... And doing any of this yourself is definately illegal.

Best regards,

Mikkel C. Simonsen
 
also, i don't know Euro wiring codes but here..

MCS,

again this was just something to mention as I don't know what is legal or illegal where the person is living. If it is illegal, please don't do it! the county i live in does NOT require the refridgerator to be on GFI, usually electricians put this on its own leg with it's own breaker. GFI IS required for outlets within something like 6 feet of a water source.

:guinness:
 
Sorry for confusing everyone I was talking about a Hi Fi (as in cd, tuner and power amp) - I think Jakob used the term HFi and then it's all got very confused
 
in Europe it is illegal to post at forums from at work too :green:
unless these have something to do with your job of course
 
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