Hi Just a quick OT Question. I have a modified 600w 12v -240v inverter and
it ran my PC fine but would not run my wife's straightening irons (75W)
whilst we where camping, (Not happy wife) is this because they have
electronic temp control. wouldn't charge a APC UPS either. Is there any mods
that can be done to the unit to round the output abit?

Andy

Andy & Kim wrote:

Hi Just a quick OT Question. I have a modified 600w 12v -240v inverter and
it ran my PC fine but would not run my wife's straightening irons (75W)
whilst we where camping, (Not happy wife) is this because they have
electronic temp control. wouldn't charge a APC UPS either. Is there any mods
that can be done to the unit to round the output abit?

You didn't have it on half power did you ? This sometimes uses as series diode.
The inverter won't like supplying half wave rectified ac.

I can tell you a funny story about this too if you like ! ;~)

Graham

I was curious about inverters too. I use 120v (US). You said you had a
story, can you tell it? Also, would you mind explaining how these work.
Pooh Bear wrote:
Andy & Kim wrote:

Hi Just a quick OT Question. I have a modified 600w 12v -240v inverter and
it ran my PC fine but would not run my wife's straightening irons (75W)
whilst we where camping, (Not happy wife) is this because they have
electronic temp control. wouldn't charge a APC UPS either. Is there any mods
that can be done to the unit to round the output abit?

You didn't have it on half power did you ? This sometimes uses as series diode.
The inverter won't like supplying half wave rectified ac.

I can tell you a funny story about this too if you like ! ;~)

Graham

nvic wrote:

I was curious about inverters too. I use 120v (US). You said you had a
story, can you tell it?

The half power series diode on hair dryers ?

A customer of my client who had one of their amplifiers I designed complained of a
noisy mains transformer. I think they sent a replacement but he said it was the same.
I visited the guy and it turned out that it was a problem only when his girlfriend's
hair dryer was on ( at half power ).

I deduced that his mains supply had a high impedance and the half wave rectification
of the hair dryer was enough to add a dc component to his ac supply which caused
excessive current in the transforrmer primary that in turn resulted in a line
frequency hum.

Not actually funny ha-ha but funny odd.

I left him to figure out how he wanted to fix it.


Also, would you mind explaining how these work.

To keep it simple. An inverter makes ac from a low voltage dc supply by various
techniques using semiconductor power devices and then steps it up to mains voltage
using a transformer. The wavefrom is rarely as purely sinusodal as your wall socket
though.

Graham

Pooh Bear wrote:


I deduced that his mains supply had a high impedance and the half wave rectification
of the hair dryer was enough to add a dc component to his ac supply which caused
excessive current in the transforrmer primary that in turn resulted in a line
frequency hum.

That probably explains why the isolating trannies on my bench vibrate
like hell when I use my heat gun on half power, even tho the gun isn't
plugged into the isolated supply.


Ron(UK)


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