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Power Inverter vs. Frequency Inverter

What is the difference between power inverter and frequency inverter? The detail analysis of inverter and frequency inverter is as following.

What is a power inverter?

Power inverter is a device that can convert DC (the battery and accumulator jar) into AC (normally the sinusoidal wave of 220V and 50Hz). It is composed of inverter bridge, control logic and filter circuit. In fact, it is a voltage inversion process with the adapter. The adapter converts the AC voltage of the mains power grid into a stable 12V DC output, while inverter converts the 12V DC voltage output by the adapter into high-frequency high-voltage AC. Now, the inverters generally use PWM pulse width modulation technology to obtain high-power, high-efficiency AC inverter output.

With a power inverter, direct current (battery, switching power supply, fuel cell, etc.) can be converted into alternating current to provide stable and reliable power protection for electrical appliances, such as laptops, mobile phones, handheld PCs, digital cameras, and various instruments. Inverters can also be used with generators, which can effectively save fuel and reduce noise. The power inverter has a wide range of uses. It can be used in various vehicles, such as automobiles, ships and aircrafts. In the field of solar and wind power generation, inverters play an irreplaceable role. It is also widely used in air conditioner, home cinema, electric grinding wheel, electric tools, sewing machine, DVD, VCD, computer, TV, washing machine, cooker hood, refrigerator, video recorder, massage device, fan and lighting device.

What is frequency inverter?

Frequency inverter, also named as VFD, is a kind of power control equipment adopting frequency conversion technology and microelectronics technology to control AC motor by changing the motor power frequency. The frequency inverter is mainly composed of rectifier (from AC to DC), filter, inverter (from DC to AC), braking unit, driving unit, detecting unit and micro processing unit, etc. The frequency converter can adjust the output power’s voltage and frequency by controlling the on and off of the IGBT. It can provide the required power voltage according to the motor demands to achieve the purpose of energy saving and speed regulation. In addition, the frequency inverter can also provide various protection functions, including the over-current protection, over-voltage protection, overload protection, etc. With the improvement of industrial automation degree, now the frequency inverter has been widely applied.

Frequency Inverter Working Principle

The above figure shows the circuit with AC frequency. P and N refer to the converter circuit. The AC can be set into DC and can be loaded to Z. When the pulse signal sent to P is sinusoidal, the set DC is sinusoidal and it is the upper half part of the sinusoidal curve. At the same time, the period is also the sinusoidal period of the pulse signal, which is an integral multiple of the AC period. The periodic sinusoidal current is generated on the load Z under the co-working of P and N. In addition, the frequency can be adjusted according to the pulse signal period. This is the working principle of the frequency inverter.

The difference between power inverter and frequency inverter

  • The power inverter is a device that can convert DC into AC and the frequency inverter is a component used to change the AC frequency.
  • The power inverter can convert DC power (battery, accumulator jar) into AC power (sinusoidal wave of 220V and 50 Hz), and the frequency can also be adjusted. The frequency inverter can convert the input AC into the AC with required frequency and then output it. The work principles include AC-DC-AC or AC-AC. The common rule is AC-DC-AC, based on which the AC is converted into DC first and then the DC is converted into AC. This is also the process of rectifying and inverting.
  • The frequency inverter includes the frequency adjustment part. However, the inverter only has fixed output frequency.
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