Let’s kick this off with a quick reminder. Variable Frequency Drives, or VFDs, are electronic devices that control the operation of an electric motor by adjusting the frequency and voltage that the motor receives.
They work by receiving the AC current from the power supply, converting it to DC then converting it back thanks to Insulated Gate Bipolar Transistors (IGBT) with variable frequency and voltage output. This is made possible by the Pulse Width Modulation (PWM) waveform that the IGBTs create.
The limit of current VFDs
VFDs allow enhanced efficiency, and optimized energy consumption. However, VFDs come with their lot of drawbacks that need to be addressed :
Voltage Spikes (reflected waves)
Voltages spikes, induced by reflected waves, create hotspots in the motor insulation material. These hotspots accumulate over the time and will lead to premature equipment failure. Using surge protective devices, ensuring proper impedance matching or having an inverter-duty motor can mitigate this side effect.
The high switching frequencies associated with VFDs lead to corona discharge, that can cause breakdown in power cables. To address this issue, people have to take VFD specified cables with suitable insulation properties and employing corona-resistant materials.
Common Mode Voltage
This is a byproduct of VFD operation. It will induce stress on motor bearings and lead to premature wear. Using insulated bearings and appropriate grounding can help counteract the effects of common mode voltage.
The PWM is one fundamental aspect of a VFD function but it has side effects that will harm the motor. One of these is rapid switching from the IGBTs. The high-frequency switching from IGBTs to create a PWM contribute to increased motor losses, and reduced overall system efficiency. Adding external output sinewave filters is a commonly used solution to mitigate the PWM effects.
Total Harmonic Distortion
VFDs generate harmonics while functioning. These can harm other equipment connected to the grid and compromise the overal power quality. To mitigate harmonic distortion, people need to add line reactors and filters in their power system.
These mitigations are really effective in addressing the problems created by traditional VFDs but they come with negative consequences for the end user but also the person in charge of the installation and the maintenance of the PDS :
- A bigger initial investment cost for the end user
- A longer installation and maintenance time for the contractor
- A less efficient and more power consuming installation
- A larger equipment footprint
What is a Clean Power VFD
These days, the industry needs to address the stakes of the 21st century: energy efficiency, carbon footprint, sustainability. The methods and technologies currently in use are not aligned with these goals. This necessitates a new solution that can harness all the advantages of integrating a Variable Frequency Drive (VFD) into the Power Drive System (PDS), without relying on traditional mitigation strategies. This solution is the Clean Power VFD. It represents a significant step forward in sustainable technology.
Total Harmonic Distortion
The Clean Power VFD maintains a THDi below 3% on both the grid and motor side, significantly reducing power quality issues.
Ideal Output Sinewave
It produces an ideal sine wave output, optimizing motor performance and preventing overheating.
Zero Common Mode Voltage
The Clean Power VFD effectively eliminates common mode over voltage. This specifically addresses bearing issues, reducing the risk of premature bearing failures and extending the overall lifespan of the motor bearings.
It’s the first VFD of its kind to operate without the need for filters, simplifying the system and reducing maintenance needs.
Superior Energy Efficiency
The Clean Power VFD reduces power consumption of the whole power drive system, delivering a noticeable decrease in energy costs.
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