Frequenzumrichter einfach erklärt: Aufbau und Funktionsweise

Summary

This video provides an overview of frequency converters and their role in electrical engineering. It explains how a frequency converter works, from converting three-phase AC voltage to DC, smoothing the voltage, and then using an inverter to produce a controllable frequency. This technology allows precise control over the speed of motors, enabling the adjustment of rotational speeds for different applications. The video also touches on technical aspects like pulse width modulation and the control unit that adjusts the output frequency. For those interested in a deeper understanding, additional resources are recommended.

Takeaways

• 😀 A frequency converter is used to control the speed of a three-phase asynchronous motor by adjusting the input frequency.
• 😀 The standard input voltage for the motor is 400V between phases and 230V phase-to-neutral, with a frequency of 50Hz.
• 😀 The motor operates at a fixed speed based on the 50Hz input frequency, but the speed can be adjusted using a frequency converter.
• 😀 A **rectifier** converts the three-phase AC input into DC voltage.
• 😀 The **intermediate circuit** smooths the DC voltage, though it is not always necessary.
• 😀 The **inverter** then converts the DC voltage back to AC with a variable frequency.
• 😀 The inverter's frequency is controlled through a **control unit** that allows the user to set a desired frequency, such as 44Hz instead of 50Hz.
• 😀 The inverter's output is adjusted via **pulse-width modulation** (PWM) to achieve the desired frequency.
• 😀 The control unit also allows for real-time adjustments and can include displays for monitoring and setting the frequency.
• 😀 The frequency converter provides the ability to vary motor speed, allowing for applications where fixed-speed motors would be insufficient.
• 😀 The overall process of using a frequency converter includes converting AC to DC, smoothing it, converting back to AC, and adjusting the frequency for precise motor control.

Q & A

What is the primary function of a frequency inverter?

The primary function of a frequency inverter is to control the speed of a three-phase asynchronous motor by adjusting the frequency and voltage of the power supplied to the motor.

How does the frequency inverter affect the motor speed?

The frequency inverter adjusts the frequency of the AC power supplied to the motor. By altering the frequency, the motor's speed can be increased or decreased, allowing for precise control over the motor's operation.

What is the standard frequency of AC power in the video example?

The standard frequency of AC power in the video example is 50 Hz.

How is the AC power input transformed inside the frequency inverter?

The AC power is first converted into DC power through a rectifier. Then, the DC voltage is smoothed by a DC-link or intermediate circuit to ensure stability before being fed into the inverter.

What role does the DC-link play in the frequency inverter?

The DC-link smooths the DC voltage output from the rectifier. Its primary purpose is to ensure that the DC voltage is stable, making it suitable for further processing by the inverter.

How does the inverter adjust the output frequency?

The inverter adjusts the output frequency through pulse-width modulation (PWM), which allows it to generate AC power with variable frequency and voltage as needed.

What is pulse-width modulation (PWM) in the context of frequency inverters?

Pulse-width modulation (PWM) is a technique used by the inverter to regulate the output frequency and voltage. By adjusting the width of the pulses, the inverter controls the average output power, enabling precise motor speed control.

What can be adjusted in the inverter to control motor speed?

The inverter's output frequency and voltage can be adjusted to control the motor speed. This is done through the inverter's control system, which allows for flexibility in motor operation.

Can the motor speed be adjusted without using a frequency inverter?

Yes, the motor speed can be adjusted using mechanical means such as gearboxes or other transmission devices. However, a frequency inverter provides more precise and variable control over the motor's speed.

What is the significance of the steering unit in the frequency inverter system?

The steering unit in the frequency inverter system is responsible for controlling the inverter's behavior. It adjusts the output frequency and voltage based on user input or sensor data, allowing the motor to operate at the desired speed.