Most new variable frequency motor drives use ac flux vector control. High power insulated gate bipolar transistors (IGBT's) are rapidly switched under microprocessor control. Few commercial drives switch current at the axis crossing - they don't use soft switching. Rather, they use hard switching.
As a result, these drives generate severe EMI which can cause catastrophic errors in ordinary torquemeters. Even standard MCRT® torquemeters, which are world renowned for their tolerance of electrical noise and machinery fields, can see errors - usually less than 1% of rating, model dependent.
Option G incorporates new technology that improves noise immunity by a factor of ten or more, compared to that of the same model without Option G. the improvement virtually eliminates EMI as a measurement factor.
Option G is available for all catalog MCRT® mV/V and DC Operated Sensors. Of the two types, DC Operated Sensors provide the greatest noise immunity. They are less vulnerable to cable noise pickup than are mV/V sensors - their output signal is high and the output impedance is very low. Two-wire Torque Transmitters will be available with Option G in Early 1999. |
For Use in severe electomagnetic interference (EMI)