MOTORS & DRIVES 5 T 26 THINGS TO CONSIDER WHEN Installing variable frequency drives in hazardous locations your application’s challenges. en, select a solution that is safe and complies with applicable regulations. Some important points to keep in mind include: Con rm that the application’s motor is approved for operation in a hazardous location with a VFD. A hazardous-duty or explosion-proof motor can only be used with a VFD if its nameplate clearly says so. at is because VFDs change motor speed by using a pulse width modulated (PWM) waveform that switches voltage on and o thousands of times per second. is rapid cycling creates harmonics that can produce extra heat inside the motor’s windings. You want a motor designed and built to operate at slow speeds without overheating and withstand higher voltage spikes, both essential in combustible situations. To confirm that your motor is approved for use with a VFD, look for two things when reviewing the nameplate: • Identi cation of the motor as inverter duty-rated and confirmation that the inverter rating suits the motor’s application. • Veri cation that the inverter duty rating clears the motor for use in the intended hazardous location. While hazardous environments pose challenges to the use of VFD-controlled inverter duty motors, they can be surmounted through careful planning, product selection and installation. By Matt Asbill, Motion , and Kyle Mertens, Nidec Motor Corporation 1 he use of electric motors with variable frequency drives (VFDs) has increased substantially in recent decades. e ben-e ts are clear: systems with VFDs operate more e ciently, use less energy, provide more precise control and reduce maintenance costs. But when a motor is in an environment with com-bustible materials, gases or liquids, VFD adoption has moved more slowly. To minimize environmental risks, many users have chosen instead to operate their haz-ardous-duty or explosion-proof motors directly from a power source. at is changing. Motors that rely on starters must be manually cycled on and off to optimize energy Processing | DECEMBER 2021 use and control demand. This creates stresses on motors and other mechanical devices, while produc-ing system output peaks. By modulating motor speed automatically, VFDs can accomplish these and other tasks with less dramatic uctuation, extending motor life and improving system efficiency. Because they control a process at speci c speeds, VFDs may also reduce the need for gear trains, belts and gearboxes. As the industry learns more about the safe applica-tion of VFDs on motors in hazardous environments, many are giving them a second look. In these situa-tions, however, not all VFDs are created equal. Before adding one to a new or existing application, it is important to conduct a system review to understand