Typical power loss of a 220 to 110V transformer - Page 1
Forum section: electronics / beginners

author: npelov
author_rank: Frequent Contributor
timestamp: September 29, 2017, 08:25:35 pm
content: Hi,I'm considering buying a refubrished 110V air conditioner. The company provides the transformer which is probably not toroidal (which would be terribly expensive at600-700W). Can someone tell me a typical loss of a transformer like this. I know it really depends on a lot of things - wire thickness, sheet quality and insulation ... blah-blah. I just need a typical figure.The AirCon will draw about 200 to 700W. The only reason I consider buying a refubrished instead of new is the efficiency - it's not much cheaper. If the transformer makes it less efficient then it might not be worth the additional point of failure.

author: wraper
author_rank: Unknown
timestamp: September 29, 2017, 08:38:07 pm
content: Don't bother with it. Besides reduced efficiency it will consume some power even when air con is off. Efficiency greatly depends on transformer, expect to loss at least 10%.

author: Benta
author_rank: Super Contributor
timestamp: September 29, 2017, 08:40:57 pm
content: At 600...700 W, I'd say that a toroid is cheaper than an EI transformer, due to significantly less copper and iron.Efficiency of that size of transformer? Certainly over 90%.Are you certain that your A/C unit, which is probably designed for 60 Hz will also run at 50 Hz?

author: wraper
author_rank: Unknown
timestamp: September 29, 2017, 08:41:49 pm
content: Also 110V appliances of the same model are a little bit less efficient than those made for 230V.

author: Zero999
author_rank: Super Contributor
timestamp: September 29, 2017, 09:23:32 pm
content: I agree that it's a bad idea.How about an autotransformer? It will have half the loss of a transformer with two windings.Also note that you need to know the current consumption, which may be higher than what would be calculated from the power, as the power factor might be considerably less than 1.

author: wasyoungonce
author_rank: Frequent Contributor
timestamp: September 30, 2017, 01:33:27 am
content: Good transformer efficiency 95~ 97% for a good unit. The losses are, heat, sound, flux losses etc.Yet there is no mention of start up current draw? Could be as high as 30% I draw more! Then leave some head room. IMHO....since at 110V it'll draw quite a lot of current compared to 230V...just doesn't appear to be the best way to go.

author: Circlotron
author_rank: Super Contributor
timestamp: September 30, 2017, 01:41:31 am
content: Quote from: wasyoungonce on September 30, 2017, 01:33:27 amTypical starting current for an induction motor is about 6 to 7 x full load current, provided the impedance of the power source is low enough.

author: Brumby
author_rank: Unknown
timestamp: September 30, 2017, 02:58:58 am
content: Quote from: Circlotron on September 30, 2017, 01:41:31 am... and you're not going to get that through a transformer which is designed for the running power consumption - which adds the question: Will the transformer provide adequate current for the motor to actually start up ... or will it just stall?

author: IanMacdonald
author_rank: Frequent Contributor
timestamp: September 30, 2017, 08:49:55 am
content: Your major concern here is if it's 60Hz equipment. On 50Hz, many such items will gradually overheat because the iron in the motor (or any internal transformer) saturates due to the longer half-cycle and hence higher inductive current build-up. Might not be noticeable in a short run either. The reverse is generally OK.

author: Circlotron
author_rank: Super Contributor
timestamp: September 30, 2017, 09:06:13 am
content: ^^ If you run it on 5/6 the rated voltage it should be okay.

author: npelov
author_rank: Frequent Contributor
timestamp: September 30, 2017, 11:39:42 pm
content: Thanks for the advices.Well maybe I'll search for better new unit. I didn't think about idle power consumption. The aircon itself has few watts idle consumption and my guess is that and very low power consumption the efficiecy will be even worse. And the 60/50 Hz might be bad but it has 3 year warranty.