A quick lesson in electrical values please
| # | Post |
|---|---|
| 1 | I need to replace the chassis mount transformer in garage door motor. The original is obsolete, so a generic unit will be required, but I am having no luck in exactly matching the output rating of 3.9 volt-amps. asmawa1 - 2021-09-27 14:09:00 |
| 2 | Yes, a higher VA rating is fine. 3.9VA is tiny, that's the size you'd solder directly to a circuit board, I would have thought a transformer in a garage door motor would be bigger than that. There's 2 important things to consider - the output voltage must be about right, I don't know what yours is but an example might be 24 volts AC. The second thing is the current, again I don't know but lets say 2 amp. You could get a higher, say 4 amp transformer and that would be fine. So my examples calculate to VA = 24 * 2 = 48VA, or the 4 amp would be 24 * 4 = 96VA. (again, 3.9VA doesn't sound enough to run a garage door motor, but it might be right if it's soldered directly to a circuit board and only powers the radio receiver and a 12volt relay to trigger another power circuit) This example of a replacement part for garage door motors has a 24 volt output and is rated at 40VA - https://www.northshorecommercialdoor.com/matrtr.html Post a photo of the transformer with a description of the make and model. Edited by gyrogearloose at 2:46 pm, Mon 27 Sep gyrogearloose - 2021-09-27 14:34:00 |
| 3 | Thanks, The unit is 240 VAC - 18 VAC. 3.9 VA. - (I took a picture to confirm the decimal point was not just a bit of dirt) Like you say the VA rating does not seem to align with the AC voltages Have to confess that I don't know how to upload photo to message board. Edited by asmawa1 at 2:54 pm, Mon 27 Sep asmawa1 - 2021-09-27 14:53:00 |
| 4 | Here's an example of an 18 volt 5VA transformer: https://nz.rs-online.com/web/p/pcb-transformers/1738958 The specs give the physical size and that it weighs 150 grams. Does your transformer weigh that little and about the size of a matchbox? gyrogearloose - 2021-09-27 15:02:00 |
| 5 | I had been on the RS website but didn't see this. The values are perfect. My unit is matchbox size but is a shrink wrapped/shellac core held in place with a horseshoe saddle. However there is a bit of space to get creative re mounting tho. Thanks very much for helping. asmawa1 - 2021-09-27 15:15:00 |
| 6 | asmawa1 wrote:
Those specs are pretty obvious, but if you want to add a photo in future... Upload a photo to your My Photos section on your My Trademe page. nzstocked - 2021-09-29 09:06:00 |
| 7 | Ya better let your insurance company know of your electrical repair plans first. tegretol - 2021-10-02 19:15:00 |
| 8 | tegretol wrote:
ECP 50 tygertung - 2021-10-02 21:04:00 |
| 9 | tygertung wrote: The first sentence under FOREWORD is the key. tegretol - 2021-10-02 22:33:00 |
