How to Choose a Suitable Power Inverter?

As a retailer of power inverters, when we received a customer call, in addition to price, the most is regular questions are: how to select the inverter for an air conditioner, television, computer or the motor? How to match the battery? How long is the service life? These are common but difficult issues. Today, we collected some information to answer these questions.

When we are going to buy a power inverter, the most concerned is not about the brand or manufacturer, as we can check out all the famous companies online. Moreover, famous brand products can be much more expensive in price than normal brands. In fact, no matter famous or normal brand, the circuit theory is the same. Experienced engineers in normal factory can design better products than famous brand. This time we put aside the brand, origin, principles, materials and other matters, and only talk about how to choose the right power inverter.

First let us look at the basic classification of electrical appliances with different types manifested in the course features:
Electrical appliances, from a technical performance that generally divided into three categories: Capacitive appliance, inductive appliances and resistive appliance.

Capacitive load - refers to the current flowing through the load leads the voltage. For example: TV, computer, mobile phone chargers and other switching power supply can be called to the capacitive load, because such electrical input of the first stage has a large filter capacitor. All electronic learners know that cross-resistance capacitance is straight through, but capacitive current than the voltage leads by 90 degrees, which means that it is for the moment the relative power wire short-circuited. So there is a kind of electrical instantaneous peak.

Inductive load - refers to the voltage leads the current, the most common are: fan, sound box (which is generally a low frequency transformer power supply), pumps, drills, air conditioners, refrigerators, etc. Its input relative power that is connected to an inductor coil, the coil is an inductor. Electronic learners understand the inductor current leads voltage than 90 degrees, which means that it is relative to the power supply is turned on instantly shorted, only after the startup of the impedance, only stable operation. When we use high-power electric motor, we will feel obviously instantaneous power, the whole house of lamps, electrical will flash, which is the peak power. Instantaneous peak power is many times greater than the motor target power. For example, standard: 500W motor, 3 times instant starting power, equivalent to the open power is 1500W.

Resistive load is the common light bulb, with respect to the power supply, it is a pure resistance, and there is no power impact problem.

Through the top of the explanation, when we choose a power inverter, it is necessary to know the impact of electrical power capacity in the moment! The motor class, because it is the emotional impact is generally 3-7 times, 500W motor power of 1500W to 3500W impact between. The inverter generally has twice the peak, which is 500W inverter, there is instant power output 1000W, 1000W has 2000W output, 1500W, there is 3000W output, 2000W, and 4000W have instantaneous output. Therefore, according to 500W motor that you want to select more than 2000W inverter, but conversely, the motor is not to say there are seven times the peak value.

As long as we understand: the inverter can output two times the instantaneous nominal power, capacitive or inductive load instantly start to 3-7 times the peak power.

How to determine the peak value is 3 times or 7 times? In fact, it is not difficult. No-load operation three times, seven times the full load operation, the number of peaks is how much we can accord the motor to drive the load to determine the degree. For example, hand drill, we are in no-load operation under normal drilling only, so we can count four times the peak (in fact, three times more than the amount of 1). 500W hand drill, four times the peak 2000W, we can use 1000W inverter. It is the same to other motors. Such as air conditioning, it is purely inductive and has a great start peak. Because every time you start the compressor, the motor is full loaded. We think it can start is 7 times the peak. 1000W air-conditioning has peak value of 7000W. Peak inverter 2 times 7000 divided by 2 equals is 3500W. That is to say, if we are going to drive 1000W air conditioner, we need more than 3500W power inverter to start it. Now the air conditioners are equipped with inverters, we can count four times the peak, 1000W inverter air conditioner, 4000W peak, to go with the safe operation of the inverter to the 2000W. Therefore, the use 1000W air conditioning, we can choose 1500W or 2000W power inverter.

Appliance like sunlamps or bulbs are pure resistance, we can match the inverter according to the power. For example: 500W inverter will be able to drive 500W bulbs. If the inverter cannot drive, prove your inverter is higher marked. According to the standard inverters, the actual output power should be able to reach 90% of marked, such as: 500W inverter can drive a minimum of 450W light bulbs, if not, the inverter is a sham product.

All above are only theory, many guests may not be able to read, or does not necessarily want to study. I listed some appliances with inverter power.

1. For purely resistive appliances like electric wire, light bulbs and sunlamps, we can use its power divided by 0.9, for example: 100W light bulbs, 100 in addition to 0.9 is 111, and a 120W inverter can be used safely.
2. Televisions have two kinds, LCD and CRT. For LCD TVs, we can choose inverter with 2 time’s larger power. For example: for a 100W LCD TV, a 300W inverter can be definitely used. For CRT, because of larger capacitive, degaussing coil and the equivalent of an inductive load, the impact is very strong, generally considered the peak of 10 times for example: 100W, peak value 1000W, we have to go with more than 500W inverter to drive.
3. For the computer, if it uses a LCD display, according to the purchase of LCD TV point plus 90W power select (mainframe computer power). If it uses CRT, select the monitor calculates the peak power plus 90W (mainframe power is generally 90W or less). If you feel trouble, use a 500W inverter will be absolutely no problem.
4. For hand drill, according to 3 times peak value (no-load and stable operation before drilling, so the peak value is low), such as: 500W peak value 1500W with 800W inverter, 1500W feature 3000W inverter.
5. For air conditioner, non-frequency peak value by 7 times, frequency 4 times. For air conditioner with 1000W per hour, 7 times is 7000W, 3500W inverter peak twice, just 7000W. Press 4 times the frequency of the count, 1000W peak 4000, 2000W inverter peak just 4000W, so the frequency also used 2000W.
6. For other smaller appliances, we do not need to consider, because a 100W inverter market price is only $500. In fact, if a general household use such as televisions, computers, stereos, fluorescent tubes, a 500W device will be OK. The price is not high for $1200. For car refrigerator, or simultaneously use several sets of home appliances, buy a 1000W inverter will do the job. The market retail price will be about $2000-3000.
7. For special purposes, such as juicer, mixing machine, big impact drill, air conditioners, freezers, etc. These appliances, the choice is indeed very difficult, please refer to 1-5 points above.

Reasonable common household battery inverter configuration:
For PC, TV and lighting, please select more than 500W inverter plus 100AH battery. Time: 4 hours.
For freezer, please select 1500W inverter plus 150AH battery. Time: 8 hours.
For fan and lighting, please select 300W inverter plus 36AH battery. Time: 2 hours.
Car refrigerator, please select more than 1000W inverter.

The power inverter using time formulas:
Battery continuously working time = battery capacity (unit: Ah) X battery voltage X 80% X 0.9÷load power
For example, 12V 100AH battery with a 100W bulb duration
=100X12X80% X0.9/100=8.64 hours
(The battery is in good or bad quality/condition, so the actual use of time may be different, but if you equip a new battery, fully charged can basically achieve the calculated time.)

The above data is based on full power product. The output waveform is suitable for pure sine wave inverter. We are looking forward to your advice and feedback.