What is an inverter?

What is an inverter?

An inverter is a power conversion device using semiconductors. It can convert direct current (DC) into alternating current (AC). You may ask, why do I need to convert DC to AC? We all know that most household appliances require AC to operate normally. In daily life, we get AC from the public power grid through the socket on the wall, and AC cannot be stored. Therefore, in some scenarios where AC cannot be directly obtained, such as power outages at home, unstable power supply from the power grid, or in the wild far away from the public power grid, you need an inverter to convert the DC stored in the battery into AC as an emergency backup power supply.

Inverter composition

DC input: generally, we call it the back panel, where the positive (red) and negative (black) terminals for connecting the battery and the cooling fan are placed.

AC output: we also call it the front panel, where the AC socket (depending on your country and location), inverter switch, inverter display, indicator light and other parts are placed.

Inverter PCB

1. Integrated Circuit (IC): composed of semiconductor transistors, it plays a core role in controlling the operation of the inverter.
2. Resistors, capacitors and inductors: used to adjust voltage and current
3. Power switching elements: MOSFET or IGBT, which are responsible for converting current between DC and AC and controlling the ideal waveform of the inverter output.
4. Solenoid or transformer: increase or decrease voltage
5. Radiator
6. Inverter housing: usually an aluminum housing, on which the power, brand and other useful information of the inverter will be clearly marked.

Inverter waveform

Inverter has three main waveforms: pure sine wave, modified sine wave, and square wave.

Square wave inverter:

The square wave design and manufacturing process are simple and cheap, but compared with the other two, its current quality is lower and its working efficiency is lower.

Modified sine wave inverter:

The modified sine wave inverter is a compromise between cost and performance. The waveform output of the modified sine wave inverter is closer to the sine wave than that of the square wave inverter, and the equipment compatibility is slightly better than that of the square wave inverter.

Pure sine wave inverter:

The pure sine wave inverter can output a sine waveform closest to the public power grid. This waveform is compatible with almost all electrical equipment, including those that are sensitive to current quality.
Its technical requirements and manufacturing requirements are higher than those of other inverters, so the price is more expensive (hundreds of dollars).

Types of inverters

Off-grid inverter

Off-grid inverters usually refer to inverters that cannot feed power back to the public power grid. They often work with batteries. It is widely used in emergency backup power systems, off-grid solar systems, and homemade off-grid power systems. Common off-grid inverters are:

1. Pure sine wave inverter
2. Modified sine wave inverter
3. Square wave inverter
4. Inverter with charging function
5. Off-grid hybrid inverter (cannot transmit power to the grid)

Grid-connected inverter:

1. Centralized grid-connected inverter: Also called central inverter, it is used in large solar power plants and wind power generation systems.
2. String grid-connected inverter: Solar panels are divided into groups; each group is connected to an inverter and equipped with MPPT to improve system efficiency.
3. Micro grid-connected inverter: Usually used for a single solar panel.
4. Home hybrid inverter: It integrates the functions of off-grid inverter and grid-connected inverter.

How the inverter works

DC power input: The inverter obtains DC power from solar panels, car batteries, truck batteries, and portable batteries.

Switching circuit

The switching circuit inside the inverter uses switching devices such as transistors (such as MOSFET or IGBTs) to switch at a certain frequency and timing to generate an alternating pulse sequence, thereby achieving high-speed switching to convert DC into high-frequency pulse current.

Forming AC waveform

Pulse width modulation technology adjusts the amplitude and frequency of the output voltage by controlling the on-off time ratio of the switching device. The controller will generate a corresponding PWM signal according to the target output voltage requirements, control the switching time and frequency of the switching device, and keep the output voltage stable and close to the target sinusoidal waveform.

Filtering circuit

The sine wave inverter needs to add a filtering circuit at the output end to filter out the harmonic components and noise in the output waveform. The filtering circuit generally uses an LC filter, which filters out high-frequency noise and harmonic components through a combination of inductance and capacitance, thereby obtaining a pure sinusoidal output.

AC output

Output: AC power that can be used by the load or connected to the public power grid.

Application of inverter

Emergency backup power supply

Power outage? Don’t worry! JCPOWER’s inverter quickly converts the DC power stored in the battery into AC power so that basic needs such as lighting, fans and mobile phone charging in the home can be met in an emergency, bringing a worry-free sense of peace of mind.

Outdoor and mobile power

You can easily carry a power inverter when you are on an outdoor adventure or RV trip. It can efficiently convert the DC power of the car battery into AC power, providing a steady supply of power for outdoor lighting, portable appliances and electronic devices, allowing you to enjoy the convenience of electrical appliances while away from the city.

Solar power generation system

Solar inverters convert the DC power generated by solar panels into high-quality AC power, making your power life more environmentally friendly. You can use a combination of solar inverters + solar panels to build a home solar power generation system. By using different solar inverters, you can decide whether your solar power generation system is off-grid or on-grid.

Uninterruptible power supply

An uninterruptible power supply (UPS) is a system that provides a continuous, stable and uninterrupted power supply to electronic devices. When the main power supply is interrupted, the UPS will automatically switch to the backup battery power to ensure that the equipment continues to work.

solar street lights

High-brightness solar LED street lights usually require higher voltage and power. The inverter can convert the direct current generated by the solar panel into alternating current that meets the needs of LED lamps.

Inverter-related terms

1. Direct current (DC): Electric current flows in only one direction and is usually stored in batteries.
2. Alternating current (AC): A type of current whose current and voltage directions change periodically. We get AC from wall sockets, which cannot be stored.
3. Frequency: The number of times the AC voltage changes, usually measured in Hertz (Hz). In most countries, the AC frequency is 50Hz or 60Hz.
4. Waveform type: The AC waveform output by the inverter, including sine wave, modified wave and square wave.
5. Rated power: It indicates the maximum power that the inverter can provide, usually in watts (W) or kilowatts (kW). The greater the output power, the more appliances the inverter can drive.
6. Conversion efficiency: It reflects the efficiency of the inverter in converting DC to AC, usually expressed as a percentage. High conversion efficiency means less power loss and higher energy utilization. Choosing a high-efficiency inverter can save energy costs and extend battery life. Normally, the conversion efficiency of the inverter is between 80% and 94%. The conversion efficiency of JCPOWER’s inverter can reach up to 94%.
7. Peak power: The maximum power that the inverter can provide in a short period of time, which is usually higher than its rated power (twice the rated power). This parameter is especially important when starting equipment with large current, such as refrigerators, air conditioners, etc. Note that there are many bad merchants who advertise the peak power of the inverter as the rated power, so that they can attract you to buy it at a very low price. The inverter cannot work at peak power for a long time, which will cause permanent damage to the inverter.
8. Total harmonic distortion (THD): The proportion of harmonic components in the output waveform, usually expressed as a percentage. Lower THD means a purer output waveform, suitable for sensitive electronic equipment.
9. Protection function:
   Overload protection: prevent damage caused by the load exceeding the rated power of the inverter.
   Overheat protection: prevent failure caused by excessive inverter temperature.
   Short circuit protection: Prevent safety hazards caused by short circuits.
   Low voltage protection: Avoid damage caused by excessive discharge of the battery.
   High-voltage protection prevents equipment damage caused by excessive input voltage.
10. Input voltage: refers to the DC input voltage required by the inverter, usually expressed in volts (V). Common input voltages are 12V, 24V and 48V. Choose the right input voltage to ensure that the inverter can work properly and match the battery or power system.
11. Output voltage: The AC voltage converted by the inverter is usually 220V or 110V (depending on the country and region where you are located). This parameter determines whether the inverter can power the household appliances we use daily. Make sure that the output voltage is consistent with the equipment requirements to avoid failures caused by voltage mismatch.

Conclusion

After JCPOWER’s comprehensive and detailed introduction, you should have a deeper understanding of the structure, types, application environment, and related professional terms of the inverter. Choosing a suitable inverter will bring great convenience and security to your life and work. JCPOWER is committed to providing customers with the best inverter products and services to meet the needs of different application scenarios. We believe that through continuous innovation and hard work, JCPOWER will become your best partner in energy solutions.

Frequently Asked Questions