1. Sensitivity to Line Voltage Fluctuations

Concern: Due to the integral power electronic components of a VFD, these devices are sensitive to power supply fluctuations such as voltage spikes and dips. These fluctuations are one of the most common causes of VFD failure. In order to compensate for an unstable power supply, additional components such as external Line Reactors need to be used, which adds to the material cost, installation time and overall enclosure dimensions.

Solution: Siemens G120 VFD drives have built-in DC reactors which eliminate the need for external Line Reactors.

2. Harmonic Distortion

Concern: Harmonic distortion can be attributed to almost all fast-switching power electronic devices. These distortions cause nuisance tripping of protective components and stability issues for the grid. As a result, electrical power providers such as BC Hydro have strict requirements for Total Harmonic Distortion (THD) levels allowed for each system. Based on their size and technology, VFDs can potentially cause significant Harmonic distortion. Note that, according to IEEE 519 standard, the THD levels should be calculated at the Point of Common Coupling (PCC), not upstream of each drive.

Solution: Harmonic filters are usually needed. However, the built-in DC reactor in the Siemens G120 drives significantly reduce Harmonic content at the PCC, potentially eliminating the need for a harmonic filter.

3. Downtimes

Concern: For mission critical and high cost operations such as municipal pump stations, the number one priority is to reduce downtimes.

Solution: VFD troubleshooting, replacement and reprogramming needs to be done in a timely manner. A modular drive such as the G120 will make field replacements easier and less costly. Also, a user-friendly interface will go a long way. Want to learn more about G120? Read our Product Spotlight which also showcases what we carry in stock.

4. Communication

Concern: Control systems technology is advancing each day enabling more devices to communicate with each other. However, there is a variety of proprietary communication protocols in the control systems industry.

Solution: All critical components, especially VFDs, should be able to accommodate most of the industry standard protocols (e.g. Ethernet IP, PROFINET, etc.).

5. Durability and Maintenance

Concern: Due to the high cost of large VFDs, their durability and lifetime are key considerations.

Solution: Do not sacrifice cost for quality. Select a manufacturer with global reputation. Siemens VFDs are known for their quality and durability. They are designed to operate for at least 10 years. Moreover, internal fan replacement is not required prior to the 10 years of service life.