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stoic

Certain loads seems hard on Inverters?

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I have come across two devices in our house that seems to put strain on the Inverters.

  1. Hair Dryer
  2. Hair Straightener 

I ASUME it is putting strain on it, cause even though the load is not nearly as much as my geyser, the inverters sounds as though they are working hard when the wife uses one of those two devices.

The standard humming noise of the inverter is a lot louder, even more so than when the geyser is on.

Question, is this bad for the inverter and should we look at maybe replacing the devices?... also.... why would it cause the inverter to hum so much?

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Generally one only uses a hair dryer when their hair is wet, which would be straight after a bath or shower.
A geyser also generally only pulls its maximum draw straight after a bath or shower.

So the dryer might be 2000w the geyser element is maybe 3000w - at this point you are at almost 5000w excluding other appliances, this is quite close to the size of many inverters (not sure what size your inverter is) - so is probably pushing the inverter near its limits.

Try turn the hair dryer on before the bath/shower while geyser is not active and likely you won't experience the same hum.

A solution might be to use a geyserwise or similar to control your geyser heating time so that geyser and hairdryer are less likely to happen simultaneously.

Edited by mmacleod
Add a potential solution

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11 minutes ago, mmacleod said:

Generally one only uses a hair dryer when their hair is wet, which would be straight after a bath or shower.
A geyser also generally only pulls its maximum draw straight after a bath or shower.

So the dryer might be 2000w the geyser element is maybe 3000w - at this point you are at almost 5000w excluding other appliances, this is quite close to the size of many inverters (not sure what size your inverter is) - so is probably pushing the inverter near its limits.

Try turn the hair dryer on before the bath/shower while geyser is not active and likely you won't experience the same hum.

A solution might be to use a geyserwise or similar to control your geyser heating time so that geyser and hairdryer are less likely to happen simultaneously.

 

The tests was done sperately, each item being the only item at the time of testing. 

Geyser (2.1kw draw) - barely any noise
Kettle (1.4kw draw) - barely any noise
Microwave (2.2kw draw) -barely any noise
Big Geyser (4.6kw draw) - barely any noise
Hair Dryer (1.7kw draw) - inverter hums a lot
Hair Straightener (0.8kw draw) - inverter hums a lot

It seems like there is sommin about those two "long hair" appliances that is difficult .... much like their operator :) 

Edited by stoic

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33 minutes ago, stoic said:

I have come across two devices in our house that seems to put strain on the Inverters.

  1. Hair Dryer
  2. Hair Straightener 

I ASUME it is putting strain on it, cause even though the load is not nearly as much as my geyser, the inverters sounds as though they are working hard when the wife uses one of those two devices.

The standard humming noise of the inverter is a lot louder, even more so than when the geyser is on.

Question, is this bad for the inverter and should we look at maybe replacing the devices?... also.... why would it cause the inverter to hum so much?

Yes, hair dryers usually have diodes on the heater on some settings - inverters do not like that. Straighteners usually have some form of control like a triac, but I do not have a lot of experience on them.

Do an experiment - test if the hair dryer causes the sound on max heat and fan.

Edited by P1000

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6 minutes ago, stoic said:

The tests was done sperately, each item being the only item at the time of testing. 
...
It seems like there is sommin about those two "long hair" appliances that is difficult .... much like their operator :) 

Ahh curious, they must be introducing some kind of interference/noise then, interested to hear what it ends up being and how it can be worked around.

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22 hours ago, P1000 said:

hair dryers usually have diodes on the heater on some settings

I was just about to say the same thing. The "half power" setting puts a diode in the line of the heater. Then only half of the sine-wave passes through the heater, and the normal 50Hz hum changes into something that resembles a 25Hz square-with-round-top wave that sounds quite a bit different.

Heat guns do the same thing.

My bean-to-cup machine also does some kind of pulsing thing and the inverter literally sounds like someone is loudly and slowly strapping cable-ties...

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58 minutes ago, plonkster said:

I was just about to say the same thing. The "half power" setting puts a diode in the line of the heater. Then only half of the sine-wave passes through the heater, and the normal 50Hz hum changes into something that resembles a 25Hz square-with-round-top wave that sounds quite a bit different.

Heat guns do the same thing.

My bean-to-cup machine also does some kind of pulsing thing and the inverter literally sounds like someone is loudly and slowly strapping cable-ties...

Bean-to-cup is most likely doing cycle skipping - where it would switch on one cycle and off for a couple.

(If you pass 50Hz AC through a diode, it is still 50Hz. If you pass it through a full-wave rectifier, you get 100Hz. To get to 25Hz, you need a flip-flop 😝 )

 

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13 minutes ago, P1000 said:

(If you pass 50Hz AC through a diode, it is still 50Hz. If you pass it through a full-wave rectifier, you get 100Hz. To get to 25Hz, you need a flip-flop 😝 )

Oh dear, yes, you are right 🙂

 

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I suspect that the noise is related in some way to the control system trying to maintain a constant output voltage. With non-sinusoidal loads, the instantaneous power would vary rapidly, so the output voltage would chop around somewhat randomly (depending sensitively on the control system gains) and the inverter would be chopping around its PWM amplitude. This may cause power to flow to and from the load to the filter L and C... Or the current surges may cause magnetostriction effects... Ok, my theory starting to sound a bit kooky.

I notice lights flickering when I run my Atten solder reflow station. Do you notice the lights flickering, @stoic?

Edit: I think I recall someone getting relief using a mains filter between the outlet and the offending appliance. Might be worth a try?

Edited by Coulomb

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16 hours ago, plonkster said:

My bean-to-cup machine also does some kind of pulsing thing and the inverter literally sounds like someone is loudly and slowly strapping cable-ties...

@plonkster It's telling you to upgrade to a Rocket Espresso machine ;) hehehehehehe . that Cable-ties sound is morse codes :) 

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4 hours ago, Coulomb said:

I suspect that the noise is related in some way to the control system trying to maintain a constant output voltage. With non-sinusoidal loads, the instantaneous power would vary rapidly, so the output voltage would chop around somewhat randomly (depending sensitively on the control system gains) and the inverter would be chopping around its PWM amplitude. This may cause power to flow to and from the load to the filter L and C... Or the current surges may cause magnetostriction effects... Ok, my theory starting to sound a bit kooky.

I notice lights flickering when I run my Atten solder reflow station. Do you notice the lights flickering, @stoic?

Edit: I think I recall someone getting relief using a mains filter between the outlet and the offending appliance. Might be worth a try?

Usually the voltage control is PID, well the point is that the response is at least delayed by one sample. The atten uses cycle skipping as well, so the output of the voltage control algorithm will always be wrong, causing flickering. The effects you are referencing would be more likely with leading/trailing edge control, with cycle skipping, at least switching is always at the zero-cross.

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5 hours ago, Coulomb said:

Edit: I think I recall someone getting relief using a mains filter between the outlet and the offending appliance. Might be worth a try?

never heard of a mains filter though, will have to check it out.

is the noise actually bad for one's inverter?

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18 hours ago, stoic said:

is the noise actually bad for one's inverter?

Hard to say. I feel uncomfortable letting the inverter "suffer" like that; it seems like it might stress the components a bit more, when some of the adjustments gets extreme. In my case, I'd do it just to stop the lights flickering; that's bad for me😬

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5 hours ago, Coulomb said:

I feel uncomfortable letting the inverter "suffer" like that

It probably also depends on the topology in use. With an old-school low-frequency device, it's probably less of an issue than it would be with a high-frequency design.

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1 hour ago, plonkster said:

It probably also depends on the topology in use. With an old-school low-frequency device, it's probably less of an issue than it would be with a high-frequency design.

It probably has more to do with the control algorithm. With high-frequency inverters you can also control faster.

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Interesting topic, just out of interest a while back I done some welding in the garage, I used my old oil bath welder and not my inverter welder because the oil bath was closer to the job, My home were running off grid at the time. I got a nice surprise when I realised my welds where as smooth with the oil bath welder as like when using my inverter welder. Even the  sound was similar to that of my inverter welder, which has that distinct inverter welding sound. So I guess you can turn a old school oil bath welder into a inverter welder.🙂

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11 hours ago, Gerrie said:

I got a nice surprise when I realised my welds where as smooth with the oil bath welder as like when using my inverter welder

Interesting. I was told its the DC that makes the difference.

My father had a Hobart engine-driven welder. Man, that thing was a beast. I kinda sorta learned to weld on that, but as it often goes when fathers teach their sons, I sort of avoided the interaction, because I am not a fast learner when it comes to such things 🙂 I do remember how easily you drew an arc with that machine.

Then for years I welded with an air-cooled AC jobbie so when I got back to a DC welder a few years ago it was a revelation again.

There is one thing I do remember: One day I switched from the hardware store brand rods to Vitemax (mostly because on that particular day it was all they had). I realised decent rods makes the largest difference in the welding experience, far more than the kind of machine you use.

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