Pumping applications in the water and wastewater industry are increasingly incorporating VFDs as a means of improving efficiency. Applications that would previously require mechanical methods for regulating the flow rate of water can be controlled directly at the pump motor with a VFD.
To ensure smooth and reliable operation, it is important to use proper VFD cabling, even when filters and other motor protection devices are used. VFD applications are susceptible to high voltage spikes that put a lot of stress onto thermoplastic insulations, like THHN, and can cause insulation breakdown. A proper VFD cable uses thermoset insulation, such as XLPE, that has a high voltage breakthrough resistance to avoid downtime.
In pumping applications, the proper cabling solution plays an even more important role as humid and wet conditions can accelerate the insulation breakdown process. Exposure to moisture can greatly lower an insulation’s ability to handle voltage spikes. Some insulations, such as PVC/Nylon, can have their Corona Inception Voltage (CIV) lowered by as much as 65% in high humidity. CIV is the voltage level at which a continuous electrical discharge will occur around the conductor. This arcing will begin when spikes reach about the CIV level and will continuously weaken the insulation until the voltage drops below the extinction voltage level. Corona Extinction Voltage (CEV) also greatly decreases in wet and humid environments and can be as low 500V, which is well below the DC bus voltage on most 480V drives. In other words, a cable not suited for wet environments can experience arcing at a much lower voltage level than in dry conditions and for longer periods of time. Additionally, each time arcing occurs the damage to the insulation further lowers the CIV level, making future arcing more likely.
To mitigate these arcing issues, it is important to specify a cable with insulation that maintains great electrical properties in wet environments. LUTZE DRIVEFLEX® uses a wet rated XLPE that maintains a much higher CIV and CEV than PVC/Nylon in wet and humid environments. Many LUTZE DRIVEFLEX® cables carry a Submersible Pump rating for installation submerged directly in water, making DRIVEFLEX® the ideal cable solution for VFDs in the water and wastewater industry.
To learn more about LUTZE’s DRIVEFLEX® VFD Cable, click the link below and your Account Manager will be in touch.
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