What's the effect of using a 60Hz transformer at 50Hz? - Page 1
Forum section: electronics / beginners

author: nsled
author_rank: Contributor
timestamp: June 27, 2023, 09:37:06 am
content: What is the relationship between frequency and transformer design?So running 60Hz transformer at 50Hz?What about running 50Hz transformer at 60Hz?What is the effect?In personal terms I have a 60Hz 240v Staco variac but live in Australia where its 50Hz, but I'm interested in what happens in other examples too. For example what about a more extreme example running a microwave transformer at 20kHz?

author: Berni
author_rank: Super Contributor
timestamp: June 27, 2023, 09:42:58 am
content: Running a 50Hz transformer on 60Hz is perfectly fine every time.Opposite is the issue.The longer cycles of 50Hz will magnetize the core more before the sine cycle turns around. Depending on how much headroom the transformer core has, it could result in a higher idle current draw, or it could go into saturation and draw a huge amount of current and overheat after a while.Tho variacs are usually not designed quite so on the edge, so it will likely work fine.EDIT:Oh and running a microwave oven transformer at 20 kHz would not work well because those transformers have a iron laminate core. So you would get large eddy currents in the core at such a high frequency, effectively turning it into an inductive heater. These iron laminate cores are generally usable up to about 400 Hz in a lot of cases. Higher up you need to go to ferrite cores.

author: Kleinstein
author_rank: Super Contributor
timestamp: June 27, 2023, 09:51:18 am
content: To keep the same level of magnetization when using 50 Hz compared to 60 Hz one would need to reduce the voltage by the factor 5/6. So ideally only 200 V at 50 Hz.

author: killingtime
author_rank: Regular Contributor
timestamp: June 27, 2023, 11:06:58 am
content: >>What's the effect of using a 60Hz transformer at 50Hz?The transformer core will edge closer to magnetic saturation meaning it will draw more current at idle (no secondary load) and heat up more. How much more current at idle and how hot depends on how close to saturation the core was designed to be in the first place. Microwave transformers are pushed hard into saturation at idle by default (high reactive current at idle). A standard multipurpose transformer much less so.

author: radiolistener
author_rank: Super Contributor
timestamp: June 27, 2023, 12:00:30 pm
content: There are two possible issues, one is a core saturation, and second is less efficiency due to insufficient inductance of the coil. But it depends on the transformer. It can works ok if it was designed with a parameters margin.

author: nsled
author_rank: Contributor
timestamp: June 27, 2023, 07:06:01 pm
content: Thankyou.I've been reading a bit more and from what I understand if you feed it a sine wave you will never get a perfect sine wave out if it saturates, and that extra energy loss is converted to heat.So I guess a suitable test method would be to feed it a variable frequency until voltage drops (frequency too high) or when the waveform distorts (frequency too low). If this is true, is there any power supply that delivers variable sine waves at cheap price? I can only think of variable PMW's that have both variable frequency and high power, very affordable but they are square waves but that may not matter?.

author: james_s
author_rank: Super Contributor
timestamp: June 27, 2023, 07:17:06 pm
content: Why don't you just connect it to power and see what it does? If it is saturating it will hum and run hot while drawing excessive current, it's not going to blow up instantly.

author: radiolistener
author_rank: Super Contributor
timestamp: June 27, 2023, 11:30:17 pm
content: Quote from: nsled on June 27, 2023, 07:06:01 pmYou're needs to test both - distortion and amplitude.Quote from: nsled on June 27, 2023, 07:06:01 pmyou're needs transformer which is designed for lowest frequency for expected bandwidth of transformer. It's hard, because lower frequency requires more massive core and more inductance for the coil (more winding), so such transformer will be more massive and more expensive.So, the better way is to get transformer which is designed for 50 Hz, it will works for 60 Hz either.

author: Berni
author_rank: Super Contributor
timestamp: June 28, 2023, 05:20:30 am
content: Just plug it into 50Hz mains and measure how much current it is drawing. If the thing starts to buzz really loudly, starting getting hot and is drawing something like 5A while just sitting there then clearly it will not work (or at least not for very long until it overheats and starts to smoke)Because of there large mass transformers always take a while to fail. Because of this you can hugely overload or even completely short out transformers for a few dozen seconds and they won't be hurt at all. All that mass of copper and iron takes a while to actually heat up.If you wanted to more carefully test it rather than just plug it in and see, then you should connect it to the output of a variac and slowly raise the voltage until you can see the current it is drawing suddenly start to go up a lot. That's where core saturation is happening.For example a 50Hz 220V transformer will also work at:5Hz 22V25Hz 110V100Hz 440V..etc