DC/AC Inverters frequently asked questions

Q: What is the difference between Modified Squarewave (also called Modified Sinewave or Quasi Sinewave) and True Sinewave?
The Modified Squarewave output is a stepped approximation of the Sinewave.

The Sinewave output duplicates grid power.

Q: Do I need Sinewave or Modified Squarewave?
A: More and more modern appliances are now fitted with electronic control circuits that require a pure sinewave to operate correctly. In domestic Solar Power Systems where a wide range of appliances will be used we recommend to only use a sinewave Inverter. Sinewave inverters should be used for the following appliances: TV, VCR, computer, fax, printers, light dimmers, fans and any variable speed motors.

Q: What size battery bank should I use for a particular Inverter?
A: For a quick approximation take the continuous rating of the particular Inverter and divide by the battery voltage, then multiply by ten.
eg: 600W 12V Inverter requires 600 / 12 * 10 = 500 Amp Hours

Q: How does power factor affect my Inverter?
A: All Inverter ratings are specified at unity power factor, power factors other than one(1) place an additional load on the Inverter, (note Watts = VA x power factor). For example a 300 Watt load with a unity power factor presents a load of 300VA on the Inverter, where as a 300 Watt load with a 0.6 Power factor presents a load of 500VA on the Inverter.

Q: Can I fit an inverter with a RCD to a vehicle?
A: SnapTec inverters can be fitted with an earth leakage device or RCD, however in order for these devices to operate the earth and neutral must be bonded at the input of the RCD. In domestic wiring this scenario does not present any problems due to the large earth plane that can be created. However, in vehicles the inverter case which is connected to earth, would need to be connected with the vehicle chassis to provide an earth plane. This connection results in earth, neutral and battery negative being bonded together, which results in the loss of the isolation between AC and DC.

Note: When using an RCD an earth plane must be created for a fault path back to earth in order for the device to trip.

Q: Why is DC / AC isolation important?
A: If the DC and AC are not isolated the Inverter would place dangerous AC voltages on the battery terminals and greatly increase the potential for electric shock.
All SnapTec inverters are completely isolated from input to output. Active and neutral are both floating with respect to the DC input and earth.

Q: What is the benefit of a toroidal transformer vs a switchmode transformer?
A: There are 2 styles of Inverter technology. High frequency switchmode transformer and toroidal transformer technology.
Each technology has advantages and disatvantages.The high frequency switchmode Inverter is physically smaller and weights less, however it is unable to supply large currents and therefore has a greatly reduced surge capacity. The toroidal transformer, while larger and heavier, can supply large currents and is far better suited for applications which require high surge currents.
i.e. motors, fridges, power tools, microwaves, pumps, TV's etc.