AC frequency?

[DrJohnZoidberg]

I was wondering how much effect the AC frequency has on connected devices.

Our UPSes show pretty much a consistent 50Hz when connected to mains, our generator fluctuates between 48 and 49Hz.

How much tolerance do electronic devices have for this frequency variance and is it something I should be concerned about?

TIA

 

[Sinbad]

I was wondering how much effect the AC frequency has on connected devices.

Our UPSes show pretty much a consistent 50Hz when connected to mains, our generator fluctuates between 48 and 49Hz.

How much tolerance do electronic devices have for this frequency variance and is it something I should be concerned about?

TIA

Subbed. Mine does 52Hz.

 

[$m@Rt@$$]

I was wondering how much effect the AC frequency has on connected devices.

Our UPSes show pretty much a consistent 50Hz when connected to mains, our generator fluctuates between 48 and 49Hz.

How much tolerance do electronic devices have for this frequency variance and is it something I should be concerned about?

TIA

That doesn't sound good. To my knowledge you need 50 to 60 for appliances in our country.

 

[DrJohnZoidberg]

That doesn't sound good. To my knowledge you need 50 to 60 for appliances in our country.

Devices usually have a some sort of tolerance, obviously they must because nothing has blown up here yet!

I want to know if there is anything to worry about and if some sort of power conditioner would help at all with this.

 

[contrastflash]

It really depends on what you are powering. The utility grid typically fluctuates -+0.5Hz. Most electronics will be fine with small fluctuations but increasing the frequency can have a similar effect to increasing the voltage. I would say for fluctuations of about 2Hz it's nothing to worry about. Some electronics actually use the AC frequency as the clock source, so you may notice your alarm system's time go out.

Things like TVs and computers won't really feel it since they are converting the AC to DC anyway and are regulated on the DC side and smoothed out with capacitors. They will have problems if you increase the frequency too much as it will be like increasing the voltage which will fry the components.

The stuff it is more likely to mess around with would be items which use the frequency to operate like motors and microwaves. Again I wouldn't stress about 2Hz unless your generator is constantly fluctuating between 48 and 52 or something, if it's a steady 52 or or so don't stress.

 

[Napalm2880]

Not sure what the tolerance is but from what I've read here on myBB, even Eskom sometimes fluctuates below the 50Hz mark. Guys were complaining that their fong kong alarm clocks (without oscillator crystal) were losing time.

EDIT: for less hearsay and more knowledge, read the post above.

 

[Sinbad]

I get oddness when the load on my genny is very low (like below 500w) - my ups kicks in and out all the time. Doesn't log anything to show why it's doing it, the events are very short.
I was thinking that maybe the frequency was wandering upwards a bit under the low load (governor problem?) Turning on some more load stabilises everything out again.

 

[DrJohnZoidberg]

It really depends on what you are powering. The utility grid typically fluctuates -+0.5Hz. Most electronics will be fine with small fluctuations but increasing the frequency can have a similar effect to increasing the voltage. I would say for fluctuations of about 2Hz it's nothing to worry about. Some electronics actually use the AC frequency as the clock source, so you may notice your alarm system's time go out.

Things like TVs and computers won't really feel it since they are converting the AC to DC anyway and are regulated on the DC side and smoothed out with capacitors. They will have problems if you increase the frequency too much as it will be like increasing the voltage which will fry the components.

The stuff it is more likely to mess around with would be items which use the frequency to operate like motors and microwaves. Again I wouldn't stress about 2Hz unless your generator is constantly fluctuating between 48 and 52 or something, if it's a steady 52 or or so don't stress.

Thanks for the input.

Not going to stress about it too much then, fridges are already not on the generator circuit and microwave gets unplugged when changeover happens.

 

[contrastflash]

For such a small fluctuation I'm not sure I'd even worry about the microwave and fridges. To just clarify my other post because I wasn't being very accurate. You get different types of loads, resistive, inductive and capactive. Purely resistive load (like heaters, geysers and kettles etc) won't be affected at all with a change in frequency. The biggest problem is inductive loads, and transformers and motors unfortunately fall into this catagory - an increase in frequency is actually going to decrease your current (I had it the wrong way before) because the inductive reactance which is similar to resistance in an AC circuit will increase with increasing frequency. The capacitive reactance on the other hand will decrease.

So in some respects if your frequency is going to change you probably want it to be higher not lower because lower might cause the current in the transformers to increase causing too much heat. Again though, for such a small change I don't think it's cause for concern. The problem is always that in today's market the margins on consumer electronic parts is so low to save money that it's unlikely that a lot of transformers would survive a greater than 5Hz decrease in frequency.