|
| Ek's Home | Forum | Chat | Electrical Links | |
| Subject - noise | |
| ib26ew | i recently installed under cabinate low voltage lighting, with seperate transformers above the cabs. its on a dedicated circuit. they work great, but it seems when you have a radio plugged in on a small appl. ckt. with it being on, then turn the low voltage lights on you hear a buzzing noise, maybe something to do with radio frequency???? |
| JimmyDee | Hi IB26EW, welcome to the Electrical Knowledge site. Some questions are hard to give a definite answer to but I sure there is someone out there that has had this specific problem and can give you an absolute answer. Hopefully, you will be able to give some good input to questions here as well and asking questions. If you are hearing a 60 Hz buzz, I think Radio Shack makes a filter for the radio feed. Not sure of this. This sounds like some type of electronic switching in the power supply like you get with dimmer switches. That is hard to filter but I think one from RS will do the job. |
| AVman | quote: |
| AVman | In my business of audio/visual, we see this problem a lot. Usually putting the AC outlet (or circuit) of the low voltage lightung and the outlet of the radio, on the same phase will solve this problem. To prove this theory; get an ext cord and find an outlet that is on the same phase (as the lv lighting)and plug the radio in to it.Hum goes away!!! This is assuming you know that there are 2 phases in your electrical service. |
| trekkie76 | It isn't a true 2 phase in the sense that two seperate phases are generated. it is one phase winding (secondary), that is center tapped for the nuetral.so, "A" and "B" are just the ends of one phase, with equal # of turns in relation to the center tap. The noise should go away if the lighting transformer and the radio are on the same bus in the panel, as the noise from the transformer isn't being transfered across the secondary winding of the service transformer. |
| lctrc789 | Ib26ew, avman has pretty much hit the nail on the head here, Radio shack does sell a filter that may help you out here. You can try to put on different leg of your service it may help as well. Actually yes, it is a differnt leg but on the same phase, hence forth sigle phase. It probably has a lot to do with the frequency of the phase and the sine wave that the low voltage transformers have. |
| lctrc789 | Trekkie, are you talking true 2 phase power or single phase power for a residential service. Single phase a Basic isolation type transformer really. It takes primary power (7620 volts) Secondary line is 240 volt with a center tap. The center tap is grounded and becomes a neutral or common. If you measure the voltage across the entire secondary it would be 240 volts, but if you measure voltage from either line to center tap you get 120 volts or half. The reason the voltage between the two are different is because they are 180 degrees out of phase with each other. It is probably this 180 degress that is causing the noise that he is hearng in the low voltage transformer. The waves are out phase with the frequency and causing this hum. I think that changing the two legs may help but more then likely he will be better off with a filter for this. |