QUESTION: What must be observed when using bimetal-referenced 3RV1, 3RV2 motor protection switches and 3RU1, 3RU2 overload relays on the load side of frequency converters*? ANSWER: What must be observed when using bimetal-referenced 3RV1, 3RV2 motor protection switches and 3RU1, 3RU2 overload relays on the load side of frequency converters*? The bimetals of the thermally delayed overload release switch are loaded thermally higher than usual, among others, due to harmonics. Therefore, the setting must be corrected according to the attached technical report. In case of alternating basic frequencies (speed control), the response value of the short-circuit release switch of motor protection switches changes. The response value of the short-circuit release switch of motor protection switches stated in the technical specifications refers to a basic frequency of 50/60 Hz. In case of deviating basic frequencies, the energy content of the AC half wave changes; as a result, the response value of the short-circuit release switch also changes as follows: - with f = 50/60 Hz: see technical data or selection and ordering data - with f = 5 Hz: Standard response value - 9 % - with f = 25 Hz: Standard response value - 5 % - with f = 100 Hz: Standard response value + 10 % - with f = 200 Hz: Standard response value + 20 % - with f = 300 Hz: Standard response value + 30 % - with f = 400 Hz: Standard response value + 40 %- with DC: Standard response value + 30 % (since only the rms value is available with DC). 3RV1+3RU1 technical report Appendix    TECHNICAL_REPORT.pdf (23,2 KB) 3RV1 manual data Appendix    3RV1_BEHAVIOUR_AT_FREQUENCIES_UP_TO_400_HZ.pdf (78,1 KB)   3RV2 manual data appendix    3RV2_BEHAVIOUR_AT_FREQUENCIES_UP_TO_400_HZ.pdf (245,1 KB) 3RV2 technical report Appendix    3RV2_FU_EN.PDF (122,0 KB)  3RU2+3RB3 technical report appendix    3RU2_3RB3_FU_EN.PDF (111,9 KB) *) including the use of a choke or sinus filter may need to be used to prevent nuisance tripping and overheating.