Radiated Emissions of a CNC in a GTEM Cell

Nowadays portable Computer Numerical Control (CNC) Machines are very common as a tool for manufacturing parts or as positioners application in measurement systems. Its electromechanical components, such as motors and control electronics, are elements that emit electromagnetic fields into the environment that can interfere with other systems or with their own electronics systems. This paper presents the measurements of electromagnetic emissions (EMI) of a CNC with a 24 V DC spindle motor: 10000 r/min, two 12 V stepper motors with 1.3 A phase current, phase resistance of 2.1 Ohm with a torque of 0.25 Nm, The EMI measurement was performed inside a Gigahertz Transverse Electromagnetic (GTEM) cell, which are correlated to the far field prediction for 3, 10 and 30 m, corresponding to an open area test site (OATS) or an anechoic chamber. The results show that in the near field the emissions are higher than 80 dBμV/m below 200MHz and 25 dBμV/m above 350 MHz.