## What is a converter and an inverter?

Simply put devices that changes a connected – and often varying – voltage to another desired and exact output voltage.

The connected voltage/current can be of Alternating Current (AC) or Direct Current (DC) voltage.
The voltage/current out can be of DC for example to charge a battery.
However, the output voltage may also be of AC type e.g. a sinusoidal wave to power 230VAC devices.

Therefore, the abbreviations AC and DC can be combined to unambiguously explain the converter/inverter function:
AC-AC = AC voltage IN and AC voltage OUT = converter
AC-DC = AC voltage IN and DC voltage OUT = converter
DC-AC = DC voltage IN and AC voltage OUT = inverter
DC-DC = DC voltage IN and DC voltage OUT = inverter

The size of the converter/inverter ( further on called CI ) is determined by the desired power to be delivered.
A CI to deliver 12VDC and 10ADC has an output power of 120W (12 × 10).
A larger CI to deliver 36VDC and 10ADC has an output power of 360W (36 × 10).

At all conversion losses are created.A good CI should have an efficiency of 85-95%.
This means that 15-5% of the energy consumed by the CI does not reach the output.
Instead, heat is generated that the converter must cool off. This is called energy loss.

## What is the energy loss for the two examples above if the efficiency is 85%?

For the smaller CI, approximately 141W must be used to deliver 120W.
The energy loss is about 21W.
For the larger CI, approximately 424W must be consumed to deliver 360W.The energy loss is about 64W.
The higher the efficiency of the CI, the lower the loss of energy and the amount of heat that has to be cooled.
Compare with how hot a 25 resp. 60W bulb will be for the examples above !
Simpel, low-cost CI often have low efficiency.

When converting voltages that are about 42V, the input must be galvanically insulated from the output – for personal safety reasons.
But even at low voltages it is often important that input and output are insulated.
This is to prevent the output of a DC-DC inverter from being short-circuited via the input in e.g. a vehicle.
Simple, cheap DC-DC inverters often have a common negative pole and do not have galvanically insulated inputs and outputs.