When To & When Not To Use Inverters

We DO NOT recommend that you use these products to operate the following:

• FRIDGES
• AIR COMPRESSORS
• AIR CONDITIONERS

An inverter is a device which converts 12 or 24VDC into 240VAC. The 240VAC generated is as lethal as the power in homes, and should be treated with the same respect. Inverters can be easily damaged, and connecting the input voltage terminals the wrong way around on the battery can damage the unit – be careful!!
Appliances most suitable for connection include:

• Most power tools
• Lights
• Most TVs
• Video recorders/players
• Most computers
• Fax machines
• Most audio equipment

Fluorescent lights can give a highly inductive load on start up which can damage inverters. Appliances not suitable include:

• Electric blankets
• Toasters
• Hair dryers
• Irons
• Radiators
• Heavy power tools (large angle grinders, circular saws, etc.)

Inverters will generally drive inductive loads such as electric motors, but only if the startup current is not high. Generally high startup current situations are when the motor is permanently coupled to a load such as a refrigeration or airconditioner compressor (Imagine the compressor at rest just before top dead centre you can easily realise the start up load on the motor!). Many other motors such as in drills, small angle grinders, buffers, etc. start up under virtually no load and this is usually OK for the inverter provided the tool is within the inverter rating. It needs to be pointed out that one of the major differences between a domestic power point and inverter is that the source impedance of a power point is very low compared to the inverter. This is why inverters have trouble with appliances with high start up currents and a domestic power point does not. Another thing that must be remembered is the special case of fluorescent lights with ballast chokes in them (by far the most common type). Manufacturers of fluoro lights assume that they are just going to be installed to a normal 240V 50Hz sine wave supply. They are required to supply a product that does not overly distort the mains waveform. They generally comply with this by installing a, say, 3.3μF non polarised capacitor accross the mains/neutral supply inside the housing of the lamp fitting. This is called a power factor correction capacitor. This seems to work OK for a sine wave supply from a low source impedance. When you drive such a device with modified sine wave 240V power, different things start to happen. The power factor correction capacitor presents a much greater load to a modified sine wave signal (which is a complex collection of high and low frequencies) than it would if it was a sine wave. The bottom line is to reduce this capacitor to about 0.47μF or take it out completely. Inverters are generally OK then. It is also possible for an inverter to be damaged by the surges in current generated when using standard flourescent starters. This can be prevented by replacing the starter with an electronic starter.

WHAT TO BUY – SINE WAVE OR MODIFIED SINE WAVE?

“Modified” sine wave is a crude approximation of the 240V waveform, with square wave components in it. Many appliances are OK with this.
Typically these are:

• All incandescent lighting
• Most switchmode power supplies
• Most TVs, VCRs, CD/DVD players
• Small power tools
• Fax machines
• Some audio equipment
• Computers (most)
• All incandescent lighting
• Most switchmode power supplies

Sine wave is closer to mains and those inverters are much more efficient. Most appliances work OK with the lower cost modified sine.
Sine wave inverters are best for:

• Electric clocks
• Sensitive equipment
• Electronic weighing machines
• Mains powered PA equipment
• All other TVs
• Plug pack powered equipment
• Anything where you want to get the most out of a battery charge