How to choose the right inverter？

1. What is an inverter and what does it do?

Simply put, an inverter is an electronic device that converts low voltage (12, 24, 48 volts, etc.) direct current to 220 volts alternating current. In daily life, 220-volt alternating current is usually rectified into direct current for use, and the function of the inverter is the opposite, so it is named "inverter". We are in an era of "mobile", mobile office, mobile communication, mobile leisure and mobile entertainment. In the mobile living state, not only the low-voltage direct current supplied by the battery or the battery is required, but also the 220-volt alternating current which is indispensable in the daily environment. The inverter is to meet our needs.

2. According to the output waveform, what are the types of inverters?

Mainly divided into two categories, sine wave inverter and square wave inverter. The output of a sine wave inverter is the same or better sine wave alternating current as the grid we use every day, because it does not have electromagnetic pollution. The output of the square wave inverter is the square wave alternating current of poor quality, and its positive maximum value and negative maximum value are generated almost at the same time, thus causing severe instability to the load and the inverter itself. In particular, the load capacity is poor, which is only 40-60% of the rated load, and cannot carry an inductive load. If the load is too large, the third harmonic component contained in the square wave current will increase the capacitive current flowing into the load, which will damage the power supply filter capacitor of the load in severe cases. In response to these shortcomings, quasi-sine wave inverters, also called modified sine waves, modified sine waves, and analog sine wave inverters, have appeared. The output waveform has a time interval from the positive maximum value to the negative maximum value, and the use effect is somewhat However, the waveform of the quasi-sine wave is still composed of broken lines, which belongs to the category of square waves, and the continuity is not good. In general, sine wave inverters provide high-quality alternating current, capable of driving any kind of load, but also have high technical requirements and costs. Quasi-sine wave inverter can meet most of our electricity needs, with high efficiency, low noise and low price, it is a mainstream product in the market.

3. What is "inductive load"?

Simply put, high-power electrical products made with the principle of electromagnetic induction, such as motors, compressors, relays, fluorescent lamps, etc. Such products require a much larger starting current (about 3-7 times) than the current required to maintain normal operation when starting. For example, a refrigerator that consumes about 100 watts of electricity during normal operation can start up to more than 900 watts of power. Since the inductive load will generate a back EMF voltage at the moment when the power is turned on or off, the peak value of this voltage is far greater than the voltage value that the inverter can withstand, which can easily cause instantaneous overload of the inverter, affecting the The service life of the inverter. Therefore, such electrical appliances have higher requirements on the power supply waveform.

4. What electrical appliances can the modified sine wave inverter be used for?

Modified sine waves are also divided into several types, ranging from square waves that are almost the same as square waves to rounded trapezoid waves that are closer to sine waves. Only the square wave is discussed here, which is the waveform that most high-frequency inverters can provide today. This type of modified sine wave inverter can be used in notebook computers, TV sets, video cameras, digital cameras, printers, various chargers, etc. Inverters with larger output power can also be used in small electric heating appliances such as hair dryers , electric cups, kitchen appliances, etc. However, it is not suitable to use the modified sine wave inverter to supply power for inductive loads such as refrigerators and electric drills for a long time. Otherwise, it may cause damage to the inverter and related electrical products or shorten the expected service life.

Let's look at a modified sine wave inverter applied to a TV. The TV has the following three requirements for the inverter: First, when the TV is turned on, the degaussing circuit has a huge instantaneous demand for electric energy, so the peak power of the inverter is very high. A 29-inch digital color TV has a power consumption of about 80 watts under normal working conditions, and the instantaneous power is as high as 1450 watts when it is turned on. Secondly, because the field frequency of the TV is equal to the frequency of the AC grid, the frequency of the AC output of the inverter must be accurate. Third, the inverter should not interfere with the TV. Even if the above three conditions are met, when the TV uses quasi-sine wave alternating current, there will still be a few fixed interference lines on the screen, and the color will be slightly greenish.

5. What is the efficiency of the inverter?

The inverter itself also consumes a part of the power when it is working, and its input power is greater than its output power. That is to say, the efficiency of the inverter is the ratio of the input power to the output power of the inverter. An inverter takes in 100 watts of direct current and outputs 80 watts of alternating current, so its efficiency is 80%.
When using low-power appliances below 300 watts, a typical car battery can provide about 25-55 minutes of power with the engine turned off. For example, if you only use a laptop that consumes 40 watts, the usage time will be longer. Generally, the inverter is equipped with under-voltage warning and under-voltage protection circuits. When the voltage of the battery drops to 10 volts due to long-term use, the under-voltage protection circuit starts, the output voltage is cut off and an alarm is issued to prevent the battery from being damaged due to low voltage. Accidents where the engine cannot be started.

6. What should I do if I want to use the inverter for a long time without starting the engine?

Prepare an additional battery, and connect the positive and negative electrodes with thick enough wires to the positive and negative electrodes of the original car battery, so that the independent use time of the inverter can be doubled.

7. What are the dangers of using an inverter?

The wire from the car battery to the input end of the inverter carries a large amount of current. If the quality of the wire is not good or the wire is too thin and the load exceeds the standard, it is easy to cause the copper wire to heat up and cause an accident. Therefore, it is necessary to standardize the operation during the use of the inverter.

8. How to equip a suitable inverter?

If the specification of the battery is 12 volts and 120 amps, we multiply 12 volts by 120 amps, and the output power of the battery is 1440 watts. If the inverter is 80% efficient, then we multiply 80% by 1440 watts to get 1152 watts. This means that this battery can drive an inverter with a maximum output power of 1440 watts (actually there is no such value, that is, 1200 watts). There is also an important note, when using the inverter, do not run it at full load for a long time, otherwise the life of the inverter will be greatly shortened, and the failure rate of the inverter will also increase significantly. It is best to use the inverter in a state of not exceeding 80% of the rated power, and do not use it continuously for a long time.

9. How to choose inverter products?

Inverter is a power product that works in high current and high frequency environment, and the potential failure rate is quite high. Be careful when buying. First select from the output waveform of the inverter, preferably not lower than the modified sine wave; secondly, the inverter must have a circuit protection function; finally, the reputation of the manufacturer is very important.