MICROWAVE HV TRANSFORMET MAXIMUM TEMPERATUE - Page 1
Forum section: electronics / general

author: paulc
author_rank: Contributor
timestamp: September 15, 2015, 11:15:32 am
content: I need to know what is the max. temp. that it can be operated safely.Transformer gets VERY HOT when operated even withuot load.After about half an hor I can barely touch it. (about 50º-60ºC)Is it usual or it just a bad quality one?

author: bktemp
author_rank: Super Contributor
timestamp: September 15, 2015, 11:24:53 am
content: That is normal. Those transformers need a forced air cooling when operated for a longer time period.

author: paulc
author_rank: Contributor
timestamp: September 15, 2015, 03:09:01 pm
content: I know that the operate with forced air cooling.But are they designed for continuos operation?What is the max safe temp for such transformer?

author: bktemp
author_rank: Super Contributor
timestamp: September 15, 2015, 03:44:23 pm
content: The maximum temperature depends on the insulation class:http://www.hammondpowersolutions.com/faq/what-is-meant-by-class-in-insulation/If you are lucky it is printed somewhere on the transformer.If you apply enough forced air cooling continous operation is no problem.

author: paulc
author_rank: Contributor
timestamp: September 15, 2015, 04:15:28 pm
content: This is good.Now I have some reference point.Thanks.

author: NiHaoMike
author_rank: Super Contributor
timestamp: September 16, 2015, 04:53:45 am
content: They're designed for intermittent operation.One way to make them run cooler is to use two with the primaries and secondaries in series. The main loss mechanism in those is core loss, which decreases sharply with reduced voltage.

author: bktemp
author_rank: Super Contributor
timestamp: September 16, 2015, 07:46:19 am
content: Quote from: NiHaoMike on September 16, 2015, 04:53:45 amYes and no:I did some measurements and calculations on that:Reducing the input voltage reduces the core losses (I did measure around 50W idle power for a typical MOT), but it also increases the copper resistance and therefore the losses under load. The efficiency under full load is considerably lower. So it depends on the load. They will run cooler, but the total amount of energy dissipated under full load will be higher.

author: paulc
author_rank: Contributor
timestamp: September 16, 2015, 03:59:56 pm
content: Using two of them is no solution as I have only one and it is too big already.I am not really loading them, just need the HV with a very small current.How will removing the magnetic shunts affect the magnetizing current?

author: NiHaoMike
author_rank: Super Contributor
timestamp: September 17, 2015, 05:38:05 am
content: Quote from: paulc on September 16, 2015, 03:59:56 pmMaybe use a bug zapper transformer or similar.

author: Psi
author_rank: Super Contributor
timestamp: September 17, 2015, 06:49:46 am
content: What voltage and current do you need?

author: paulc
author_rank: Contributor
timestamp: September 19, 2015, 09:24:18 pm
content: I need approx. 3-6KV, few mATransformers, diodes ans caps from MW ovens are FREE.

author: Gyro
author_rank: Super Contributor
timestamp: September 20, 2015, 04:32:32 pm
content: It may be free, but it's overkill by about 100 times in terms of deadly current capacity!

author: paulc
author_rank: Contributor
timestamp: September 24, 2015, 08:59:07 pm
content: I finished the work (Meanwhile).No people or animals were harmed during this experiment.Thanks for the help and info from all.

author: station240
author_rank: Unknown
timestamp: October 16, 2015, 12:25:41 am
content: Perhaps you could get parts out of a inverter based microwave, Panasonic is one brand.