Hair Dryer vs. Inverter mystery

HLD · Dec 30, 2022

When running a hair dryer my inverter makes this crazy resonating sound. It only happens with the hair dryer and it only happens when the hair dryer is on the low setting. No other loads i've tested, regardless of wattage, cause the inverter to make this sound. The inverter has a transformer. (EG4 6000) And is off-grid (no AC input) It is not fan noise - it is deep, whawahwahwahwannnnggg.

The advise i've received so far is:

Don't run the hair dryer on low. ( we don't )
Call an electrician?
It's probably the fan. ( it's not )
Transformers are weird, sometimes they make weird sounds.
You should have gone with Schneider.

So i'm back here seeking the counsel of you lot. Any ideas?

More about the setup:

15kwh of EG4 batteries connected to a single 240v EG4 6k. Charged by 5.3kw of solar.
AC out from inverter is wired to a single load center that is connected to a GEC and has a Neutral/Ground bond.
There is no "balancing" on the circuits. I only have 2 and the issue occurs when I plug the hair dryer into either.

400bird · Dec 30, 2022

To get low speed, the hair dryer might use PWM. Maybe the PMW frequency/duty cycle in low is causing resonance with the PWM switching inside the inverter.

I'd go with option 1, I don't think it's worth any further investigation.

Hold that option 5 in your back pocket! I love my Schneider XW, so I'm biased.

Mtrhmr · Dec 30, 2022

HLD said:
When running a hair dryer my inverter makes this crazy resonating sound. It only happens with the hair dryer and it only happens when the hair dryer is on the low setting. No other loads i've tested, regardless of wattage, cause the inverter to make this sound. The inverter has a transformer. (EG4 6000) And is off-grid (no AC input) It is not fan noise - it is deep, whawahwahwahwannnnggg.

The advise i've received so far is:

Don't run the hair dryer on low. ( we don't )

Call an electrician?

It's probably the fan. ( it's not )

Transformers are weird, sometimes they make weird sounds.

You should have gone with Schneider.

So i'm back here seeking the counsel of you lot. Any ideas?

More about the setup:

15kwh of EG4 batteries connected to a single 240v EG4 6k. Charged by 5.3kw of solar.
AC out from inverter is wired to a single load center that is connected to a GEC and has a Neutral/Ground bond.
There is no "balancing" on the circuits. I only have 2 and the issue occurs when I plug the hair dryer into either.

It probably has a half-wave rectifier. This article may explain it better than I can: https://www.fluke.com/en-us/learn/blog/power-quality/half-wave-rectifier

42OhmsPA · Dec 30, 2022

Interesting, I noticed my heat gun on med made a capacitor I installed make a weird clicking noise, now I want to remove the cap and see if I can replicate on my invertor which is essentially the same as yours.

HLD · Dec 30, 2022

Mtrhmr said:
It probably has a half-wave rectifier. This article may explain it better than I can: https://www.fluke.com/en-us/learn/blog/power-quality/half-wave-rectifier

I think you may have cracked it.
This is the exact hair dryer:

What is inside a hair dryer? (2 of 2) (video) | Khan Academy

Learn for free about math, art, computer programming, economics, physics, chemistry, biology, medicine, finance, history, and more. Khan Academy is a nonprofit with the mission of providing a free, world-class education for anyone, anywhere.

www.khanacademy.org

And this is the diagram of what they call a "bridge rectifier":

Bridge Rectifier

The fluke article you provided essentially said "no reasonable cure, use new stuff" as the solution. My mind is boggled.

Bud Martin · Dec 30, 2022

DC offset issue causes xformer noise.
Most hair dryer use diode to reduce the power in half in low mode, the heating element will only heat at 1/2 of the AC cycle, not at full cycle when on full mode.

Mains DC and Transformers

ESP - The Audio Pages. Even a small amount of DC offset on the mains is enough to cause problems. Find out how it happens and how to fix the problem.

sound-au.com

HLD · Dec 30, 2022

Option 1 of not using the hair dryer on low is definitely sounding both reasonable and lazy (in a good way). But I won't always be in control of what folks plug into this setup and what wind level they like their locks blown at.

Is there any way to mitigate the problem?
Is there more clever equipment that detects and deals with this resonance?

What about systems that don't use big 'ol honkin' transformers? Do they experience negative effects of half wave rectification?

LTV_Ken · Apr 10, 2023

Been setting up an EG4-3k inverter and trying to figure out why my old heat gun throws an "Error 16" (Over DC voltage in AC output) code when I run it on low. Can run on high, with other loads, but if I add the heat gun on low, it errors. Did a search and found this thread. This sound like the most plausible reason I have found. I opened the heat gun and found the diodes that make up the half-wave rectifier. SignatureSolar tech support has been somewhat responsive, but doesn't like the fact I don't have a load panel set up. I have a plug so I can run my generator cord to my disconnect panel, or plug in other loads in my shed. Worried about the ground path and the cord. Will pass this info on to them and see. Inverter works fine other then for this heat gun.

v_green57 · Apr 10, 2023

LTV_Ken said:
Been setting up an EG4-3k inverter and trying to figure out why my old heat gun throws an "Error 16" (Over DC voltage in AC output) code when I run it on low. Can run on high, with other loads, but if I add the heat gun on low, it errors. Did a search and found this thread. This sound like the most plausible reason I have found. I opened the heat gun and found the diodes that make up the half-wave rectifier. SignatureSolar tech support has been somewhat responsive, but doesn't like the fact I don't have a load panel set up. I have a plug so I can run my generator cord to my disconnect panel, or plug in other loads in my shed. Worried about the ground path and the cord. Will pass this info on to them and see. Inverter works fine other then for this heat gun.

Those teeny diodes you show in the image are there to make DC to run the el-cheapo slot car motor for the fan. They aren't big enuf to rectify the apx. 1kW of the resistive element and are soldered to the tabs for the motor brushes.

Most heat guns/hair dryers I've torn apart don't go half-wave DC to get a lower output. There are usually two sections to the resistive heat element. For full output, switch them both on. For half output, only one.

What I don't understand is why some inverters have a problem running one of the most common appliances on the face of the earth.

It's not the appliance's fault, it's the inverter's.

Hair Dryer vs. Inverter mystery

HLD

New Member

400bird

Solar Wizard

Mtrhmr

New Member

42OhmsPA

What's in a title?

HLD

New Member

What is inside a hair dryer? (2 of 2) (video) | Khan Academy

Bud Martin

Solar Wizard

Mains DC and Transformers

HLD

New Member

LTV_Ken

New Member

Attachments

v_green57

Solar Enthusiast

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