news@pasteur.Berkeley.EDU (Six o'clock News) (12/28/90)
>In article <9624@ncar.ucar.edu> hpoppe@ncar.ucar.edu (Herb Poppe) writes: >|Does the "LV" stand for "Low Voltage"; if so, what is the voltage? > >Yes, 12 V. I don't know if it's AC or DC. > >The lamp has a power supply/transformer which takes 120 VAC >and converts it to 12 V. (I don't know if it's really a >transformer or some cute solid state thing, it does say not >to use it on a regular lamp dimmer so I suspect it's SS in some >way.) > From: charless@cory.Berkeley.EDU (Charles R. Sullivan) Path: cory.Berkeley.EDU!charless This doesn't indicate whether it is SS or not. Transformers can have serious problems when driven by the output of a 'normal' dimmer. This is because the dimmer can be somewhat assymetric, and put some dc voltage on the transformer primary. Since the primary is nearly a short for dc, it draws lots of current, perhaps the core saturates, and the transformer can overheat, a serious fire hazard. 'SS transformers,' which are usually a rectifier, followed by a 25kHz inverter, followed by a high frequency transformer, and usually put out 25kHz ac to the lamp, have other problems on normal dimmers, notably flickering, acoustic noise and possibly shortened life of the SS transformer and the dimmer. *****Warning: Blatant commercial plug follows.****** Dimming both types is possible--just make sure you use a dimmer designed for that purpose. The company I used to work for, Lutron Electronics, makes both types in a variety of styles. Call 800 433 3334 (800 523 9466 in PA) for more info. Charlie Sullivan charless@cory.berkeley.edu
phil@brahms.amd.com (Phil Ngai) (12/29/90)
In article <9949@pasteur.Berkeley.EDU> charless@cory.Berkeley.EDU writes: |>The lamp has a power supply/transformer which takes 120 VAC |>and converts it to 12 V. (I don't know if it's really a | |This doesn't indicate whether it is SS or not. Transformers can have serious Ok, I took apart my Crest Low Voltage Halogen Track Light, which uses a GE MR-16 50 W bulb. It is solid state. There is a bridge rectifier followed by a smallish capacitor feeding a couple of power transistor looking devices (could be MOSFETs, I don't know) which drive a small transformer. Obviously they are using high frequency voltage conversion to reduce the size of the package, trading silicon for iron. -- Whatever happened to Global Warming? Could we have some Local Warming?