How the components of the inverter work – Delta

1. Inverter element - rectifier

Since it is difficult to change the frequency of the communication sine wave in the form of communication, the first operation of the inverter is to convert the waveform into direct current. To make it look like an AC, it is relatively easy to operate the DC. The first component of all inverters is a device called a rectifier or converter, and the inverter rectifier circuit converts communication power into direct current, which works in much the same way as a battery charger or arc welder. It uses a diode bridge to restrict the communication sine wave from moving in only one direction. The result is a fully rectified communication waveform that is interpreted by the DC circuit as a local DC waveform. A three-phase inverter accepts three independent communicating input phases and converts them into a single DC output.

Most three-phase drives are also capable of accepting single-phase (230V or 460V) power, but since there are only two input branches, it is necessary to derate the converter output (HP) due to the proportional decrease in the DC current that occurs. On the other hand, a real single-phase inverter (a single-phase inverter that operates a single-phase motor) utilizes a single-phase input and generates a DC output that is proportional to the input.

When it comes to variable speed operation, there are two reasons why three-phase motors are more ubiquitous than single-phase counter components. First of all, they have a wider power range. Single-phase motors, on the other hand, usually require some external intervention to start spinning.

How the components of the inverter work – Delta

How the components of the inverter work – Delta

2. Inverter components - DC bus

The DC bus is the second component, which is not visible in all inverters, as it does not directly affect the inverter operation. However, it is always present in high-quality universal frequency converters. The DC bus uses capacitors and inductors to filter out the communication "ripple" voltage in the converted DC current, which then enters the inverter section. It also contains a filter that prevents harmonic distortion and is able to feed back to the inverter power. Older drives and separate line filters are required to complete the process.

3. Inverter components - inverters

The inverter uses three sets of high-speed switching transistors to create all three-phase DC "pulses" that simulate the communication of sine waves. These pulses determine not only the voltage of the wave, but also its frequency. The term inverter or inverter means "reversal", which is simply the up-and-down movement of the waveform that takes place. Modern AC converter inverters use a technique called "pulse width modulation" (PWM) to regulate voltage and frequency.

Then let's talk about IGBTs, which refer to "insulated-gate bipolar transistors", which are the switching (or pulsing) elements of an inverter. Transistors (instead of vacuum tubes) serve two roles in our electronic world. It can act as an amplifier and increase the signal like an amplifier, perhaps acting as a switch, simply turning the signal on and off. IGBTs are a modern version that offers higher switching speeds (3000 - 16000 Hz) and reduced heat generation. Higher switching speeds can improve the degree of communication radio wave simulation and reduce motor noise. The less heat that occurs means a smaller heat sink and therefore a smaller footprint for the drive.

Fourth, the PWM waveform of the inverter

The waveform of the inverter of a PWM inverter is shown compared to a real AC sine wave. The inverter output consists of a series of rectangular pulses with a fixed height and adjustable width. In this particular case, there are three sets of pulses - a wide set in the middle and a narrow set at the beginning and end of the positive and negative parts of the AC cycle.

The sum of the areas of the pulses is equal to the effective voltage of the real AC wave. If you were to cut out the pulses above (or below) the real communication waveform and fill in the empty space below the curve with them, they would be a perfect match. It is in this way that the inverter can control the voltage of the motor. The sum of the pulse widths and the width of the blank space between them determines the frequency of the waveform seen by the motor (hence PWM or pulse width modulation). If the pulse is continuous (i.e. there are no gaps), the frequency is still correct, but the voltage will be much larger than the real AC sine wave.

Depending on the required voltage and frequency, the frequency converter will change the height and width of the pulses and the width of the gap between them. Some of you may wonder how this "fake" AC (actually DC) runs a communicative induction motor. After all, is there a need for a communication electrical current to "induce" the current in the motor's rotor and its corresponding magnetic field? Well, AC naturally causes induction, since it is constantly changing direction, on the other hand, DC does not behave normally due to the fact that once the circuit is activated.

However, if the DC is open and closed, the DC can sense current. For those of the age, car incineration systems (before solid-state incineration) used to have a set of points in the dispenser. The intent of these points is to "pulse" from the battery to the coil (transformer). This induces an electric charge in the coil, which then raises the voltage to a level that is acceptable for spark plug incineration. The wide DC pulses seen in the diagram above are actually made up of hundreds of individual pulses, and this open and closed motion of the inverter output is promised to occur through DC induction.

How the components of the inverter work – Delta

Sections viewed

Contact

working hours