I have dozens of VFDs used to run submersible pumps in an oil field. A particular line of VFDs has been struggling with VFD Overtemperature issues in the summer heat. I have noticed that if I get the drive output voltage above 450 V, the VFD heat sinks are cooler and avoid the temperature shutdown. It also appears the closer the output voltage is to the input voltage (480V), the cooler the VFDs run. Can anyone help explain why this is?