Since the formal implementation of the ATEX specification in July 2003, the control and monitoring standards for explosion-proof motors have become particularly stringent. This specification assigns the thermistor input for motor temperature monitoring to the safety device and specifies that all components must comply with the ATEX standard. Vacon has partnered with the German BGIA test facility and the VTT Technical Research Centre in Finland to develop a built-in thermal input solution for inverters that meet ATEX certification requirements. In 2006, Vacon's motor overtemperature protection technology was certified to the ATEX 94/9/EC specification. Although this technology still does not allow the inverter to be installed directly in a hazardous area, it is one of the few solutions available on the market and has been applied to a certain extent. The KemFine chemical plant in Kokkola, Finland, produces high-purity chemicals for the agrochemicals and pharmaceutical industries, requiring the use of approximately 200 solid and liquid chemicals and raw materials. Most of its production facilities are located within an explosive atmosphere (explosion-proof grade 1, equipment grade II2G). Therefore, safety and meeting the ATEX requirements as much as possible are the primary tasks of the plant.
The vast majority of the 1,250 motors in the plant are explosion-proof motors, using a total of approximately 250 inverters from different manufacturers. Among them, 30 Vacon NXP inverters are used for drive control of pump equipment and agitators. These inverters integrate motor over temperature protection based on ATEX thermistor input technology. Vacon motor overheat protection technology uses the same ATEX-certified integrated safety prohibition function. When the temperature sensor installed in the motor manufacturer detects excessive temperature, the inverter will automatically shut down the motor. Vacon NXP drives have the unique features of a built-in thermistor input that simplifies the control and monitoring of explosion-proof motors compared to typical legacy systems with independent thermistor relays and contactors. According to users, Vacon motor over temperature protection has many advantages. The circuit diagram is simple and straightforward, eliminating the need for thermistor relays, indicator lights and reset buttons, resulting in fewer components than conventional solutions. In addition, the technology can also reduce the amount of cable used in the power distribution room, making reliability more efficient and saving space and cost. When an alarm occurs, the cause can also be diagnosed by the inverter panel operation or the field bus.