Test results from the electronics lab

For those who want to know, I've tested the unit in my electronics lab. Of course, the device generates at this price no real sine wave as it comes from the power grid. Rather, it generates a fairly clean square wave with an amplitude of 300 volts and an ON / OFF duty ratio of 5.8 to 4.2 milliseconds, that in each half cycle it turns off the 300 volts for 4.2 milliseconds. This results in an effective value of 240 volts at idle and 228 volts when loaded with a 60 watt bulb. At 100 watt load there are still 225 volts rms. From the power grid against nearly 230 Volt come effectively with an amplitude (peak value of the sine wave) from theoretically 325 volts. Measured there were only 314 volts.

What does this mean for the user? When light bulbs and heaters (so-called. Ohmic consumers) do not care, they work fine. Energy-saving lamps, LED lights, etc. might flicker possibly something more. TV and computer power supplies, which include a switching power supply, should work fine because they usually work with any voltage between 100 and 240 volts. Internally, the input voltage is rectified only once, so they can work just as well with a square-wave voltage.

It becomes more problematic in case of inductive loads such as motors and transformers. This can be in operation a little more heat than normal. Possibly well it goes down a little performance. I have the converter tested with my AER Guitar Amplifier (Compact 60), which has a toroidal transformer. That went smoothly for several hours of continuous operation, however, could be heard a faint buzzing. This comes from the steep edges of the square wave.

I have the equipment disassembled and found the building in order, albeit a little cramped and not very easy to service. But if it breaks, is not a lot of money back. Incidentally, it has a 15 amp fuse in the plug, so you have to have no fear of cable fires etc. in the car.

In principle, it is always better to work directly with 12 volts whenever you can. So an inverter typically 5-10% losses (at full load) and is therefore also slightly warm during use. Under light load the efficiency is low. Therefore it is better to recharge his cell phone with a 5 volt USB connector for the cigarette lighter.