igor@engin.umich.edu (Bryan Ebersole) (03/01/91)
I was wondering if it would be possible to build a surge suppressor to eliminate voltage spikes from a refrigerator. There is apparently only one power line running throughout my dorm room for all of the outlets, and the refrigerator (small cube type) spikes my stereo system every time it turns itself on/off. We have hooked up the system through as many as four (cheap) "full protection" surge suppressors. Is it possible to upgrade the MOVs inside, add some in series, parallel, or something like that, or do I need to be adding chokes/torroids/RFI filters? I haven't been able to find any project books detailing how to build something like this, so any recommendations on even theory type books would be appreciated (not the kind of stuff they teach us about in circuits classes). Thanks for your help, Bryan Ebersole igor@engin.umich.edu
cline@PROOF.ERGO.CS.CMU.EDU (Kenneth Cline) (03/01/91)
I think what you want is an isolation transformer. Computer dealers should be able to help you find what you need. Ken
francis@cs.ua.oz.au (Francis Vaughan) (03/01/91)
In article <1991Feb28.185322.23113@engin.umich.edu>, igor@engin.umich.edu (Bryan Ebersole) writes: |> I was wondering if it would be possible to build a surge |> suppressor to eliminate voltage spikes from a refrigerator. |> There is apparently only one power line running throughout |> my dorm room for all of the outlets, and the refrigerator |> (small cube type) spikes my stereo system every time it |> turns itself on/off. We have hooked up the system through |> as many as four (cheap) "full protection" surge suppressors. |> Is it possible to upgrade the MOVs inside, add some in series, |> parallel, or something like that, or do I need to be adding |> chokes/torroids/RFI filters? I haven't been able to find |> any project books detailing how to build something like this, |> so any recommendations on even theory type books would be |> appreciated (not the kind of stuff they teach us about in |> circuits classes). Thanks for your help, Two things. Number one, stop trying to supress the stereo system. Supress the problem not the symptom. Put a supressor on the refrigerator. Everytime it it glitches it is probably radiating EMF all over the place from the power runs in the dorm. Stop the glitch reaching the wires in the first place. If you let the refigerator radiate this energy you will pick it up in the speaker wiring, and other bits, and the supressor will be powerless to help. Second, a surge supressor is not an EMI killer by itself. If it only has MOVs in it is not going to be real useful. It will stop surges killing you computer (to a point) but if you want to stop hash you need to kill differential and common mode noise on the line. The movs will already be in all useful positions (3 connecting the three wires.) Uprating is of little use. The rating is only a thermal dissipation rating. If they haven't cooked they don't need uprating. To kill noise needs a bit of L and C. Commonly, lossy inductors are put in series with the active and neutral, capacitors dropped between active, neutral and earth, and a torroid wound with identical windings of both the active and neutral runs (so it don't saturate). Little box filters are available with MOVs and the torroids quite cheaply. I have a local magazine design for a very mean filter. Can't remember the reference right now. I can dig it out if there is any interest. Try suppressing the refrigerator first. That may do the trick. An MOV based supressor right at its power point can be quite effective. Francis Vaughan.