Inverters FAQ’s

1. What is an inverter?

An inverter takes DC power (battery or solar panel, for example) and converts it into AC “household” power for running electronic equipment and appliances that require 220v to operate

2. How is an inverter different to a UPS?

A UPS (uninterrupted Power Supply) typically includes the battery and battery charger in one stand-alone unit and usually used on computers for short time power backup. However the main principal between a UPS and an inverter is the same.

3 Is an inverter better than a generator?

It depends on the application. When not much power is consumed, as is the case in homes and various businesses like banks and furniture shops, a battery back-up is hands-down the better solution. The AMF panel of a domestic back-up generator alone costs more than the whole UPS system, installation included.

4. What if I want a DC output to run such things as a laptop from a car cigarette lighter, or telephone equipment at -48 volts?

Then you want a DC/DC converter. We do not stock these,but they can be available in 1 to 2 months from a confirmed order.

5. What is the difference between sine wave and modified sine wave?

Alternating current (AC) has a continuously varying voltage that swings from positive to negative. This has great advantages in power transmission over long distances. Power from your power company is carefully regulated to be a perfect sine wave, because that is what naturally comes out of a generator, and also because sine waves radiate the least amount of radio power during long distance transmission. On the other hand, a sine wave is expensive to make in an inverter, and many sine wave techniques use heavy, inefficient transformers. The most inexpensive way to make AC is to switch the DC on and off–a square wave. A modified sine wave is scientifically designed to simulate a sine wave in the most important respects so that it will work for most appliances. It consists of a flat plateau of positive voltage, dropping abruptly to zero for a while, then dropping again to a flat plateau of negative voltage, back to zero for a while, then returning to the positive voltage. This pause at zero volts puts more power into the 50HZ fundamental than a simple square wave does, so it is called “modified sine wave” instead of “square wave.”

6. Can I use a modified sine wave inverter for my medical equipment?

For Medical equipment, oxygen generators, etc. talk to the manufacturer of the equipment. Our inverters are never tested or rated with medical equipment, and we don’t guarantee that they will work to save your life. For these applications we recommend pure sine wave inverters.

7 What about square wave inverters?

These old-fashioned inverters are the cheapest to make, but the hardest to use. They just flip the voltage from plus to minus creating a square waveform. They are not very efficient because the square wave has a lot of power in higher harmonics that cannot be used by many appliances. The modified sine wave is designed to minimize the power in the harmonics while still being cheap to make.

8. How do I know if I need a sine wave, or if I can live with a modified sine wave?

The following gadgets work well with a modified sine wave: computers, motor-driven appliances, toasters, coffee makers, most stereos, ink jet printers, refrigerators, TVs, VCRs, many microwave ovens, etc. Appliances that are known to have problems with the modified sine wave are some digital clocks, some battery chargers, light dimmers, some battery operated gadgets that recharge in an AC receptacle, some chargers for hand tools (Makita is known to have this problem). In the case of hand tools, the problem chargers usually have a warning label stating that dangerous voltages are present at the battery terminals when charging. We would like to add to this FAQ any appliances that you have had trouble with, or had success with, using modified sine wave inverters. Please mail us at [email protected]

9. Why do I hear buzzing on my stereo when using a modified sine wave inverter?

Some inexpensive stereos use power supplies that cannot eliminate common-mode noise. These would require a sine wave inverter to operate noise-free. Filters are also commercially available, and not too expensive.

11. How should I select the right size inverter?

First add up the power ratings of all the appliances, then buy the next larger inverter! At least that is the simple answer. Note, however, that some appliances, such as table saws, refrigerators, and microwaves have a surge requirement. Inverters supplied by Clamore Solar are designed to supply such surge requirements, but since every appliance has its own requirements sometimes you will need to get a bigger inverter than you would otherwise think. Note that the inverter isn’t the only consideration when you are pondering the mysteries of start-up surges. The battery must also be able to supply the surge power, and the cables must be able to supply the increased current without dropping the voltage too much.

10. Why don’t I measure rated voltages when using a multimeter on my modified sine wave inverter?

The rated voltage is an RMS (root mean square–they square the value to make sure it is always positive, then average it, then take the square root of the average to make up for having squared it in the first place) measurement. Most multimeters are designed to give correct RMS readings when applied to sine waves, but not when they are applied to other waveforms. They will read from 2% to 20% low in voltage. Look for a voltmeter that brags’ about “True RMS” readings.

12 Why do I need such humongous cables to the battery when a small cord takes the AC output fine?

Power is volts times amps (Watts = V x A). So if you have a lot of voltage you don’t need many amps. Roughly you need 12 times as much current from the 12 volt battery as you need from the 220 volt AC outlet. Current is what causes cables to heat up, not voltage. That is why they use thousands of volts in power transmission grids. The thing to do when you have lots of current is to lower the resistance of the cable. The larger the wire the lower the resistance. Think of the cable as a water pipe. A big pipe (wire) can carry more water (current or amperage) with less pressure (voltage), and will present less pressure (voltage) drop from one end of the pipe to the other. Another consideration is how far the cable has to run from the battery to the inverter. Long cable runs are expensive, either in copper or efficiency, or both.

13. Why would you use a 24 volt inverter instead of a 12 volt inverter?

At a given power rating a 24 volt inverter will need half the current as a 12 volt inverter. This makes the entire system more efficient, and since high current transistors are expensive, the inverter will be cheaper. Many trucks and busses run their complete electrical systems on 24V.

14. Should I use aluminium wire, or must I use copper?

Aluminium is cheaper and lighter, but it also has higher resistance for a given gauge, and is more difficult to connect to. If you are an expert in such things, or know one, and need the advantages that aluminium gives, go ahead. If not, why not use the best conductor, copper? (Silver is slightly better, but it is cheaper to use a larger diameter copper). Make sure to use good insulation, 90°C rated or better. Also, running two sets of parallel wires instead of one can cut down on the wire heating due to more surface area. Make sure to follow all applicable electrical codes. Inverters must be grounded properly, and treated with respect, since they put out potentially lethal voltage.