Sine Wave Inverter Anomaly

brulaz wrote:

Gdetrailer wrote:

...
But BEFORE adding any neutral to equipment bond you MUST READ THE MANUAL OF THE INVERTER OR GENERATOR to make sure you CAN make that connection.

Heh, well the manual is useless. It is a CHEAP inverter, but it is also a PSW, so maybe that means something.

There is an online Q/A at Canadian Tire where they say not to bond, but dunno if the guy there knows anything. He talks in generalities.

Anyway I'm NOT going to try bonding it. If the EMS doesn't work, so be it. The 120V bypass relay is in transit.

Just because it is a PSW inverter, DOESN'T mean it is a GOOD QUALITY PSW inverter. Cheap inverters (including PSW) by the skimping on components use some trickery called BALANCED TRANSFORMER LESS OUTPUT (or BTL for short).

Basically put, it is similar idea that many car stereos use to get more than 4W output at 12V only in an inverter on a larger scale.

Think of it like taking two amplifiers and bridging them together. One amp gets a negative going signal and the other gets a positive signal.

So in a Balanced output stage, you have one amp with a negative 60V and the other has a positive going 60V. This creates a "floating ground" and the sum of the two is 120V.

The difference with cheap BTL inverters vs higher priced BTL inverters is one major step.. It is called ISOLATION, the cheap inverters SKIP a expensive step in the process that isolates the 12V ground from the the output of high voltage chopper circuit.

The more expensive BTL inverters will include a high frequency transformer in the high voltage chopper circuit which allows the output stage of the inverter to be "bondable" to the equipment ground.

If you take a inverter which uses BTL output without an isolated 12V input and SHORT one of the output lines to the battery ground you now only have 60V AND often the inverter has a meltdown..

If the manual does not specifically state that you CAN BOND the neutral to equipment ground then you better NOT bond.