September 2019

A US COMPANY has developed and patented a series of EMI (electromagnetic interference) filters that, it claims, resolve many of the issues associated with PWM (pulse width modulation) drives – such as the high-frequency currents that can destroy motors’bearings. California-based OnFilter says that in comparison with conventional reactors, which reduce these leakage currents by a factor of 2–3, its easy-to-install SF series dV/dt filters can reduce the currents by 50–100 times or more. And, unlike mechanical mitigation techniques that use contacts and brushes, the filters need no mechanical attachments or motor modifications, and are maintenance-free. They also reduce EMI (electromagnetic interference), whichmechanical systems cannot do. The new filters help to comply with IEC 60034- 17/-25 by smoothing the sharp edges of potentially damaging drive pulses to provide“complete” filtering – common and differential mode and in ground – thus preventing currents from flowing through the motor bearings. This will prolong the lives of motors powered by VSDs or servodrives and cut maintenance costs, as well as reducing the occurrence of disruptive“no fault found”problems, according to OnFilter. The new filters are rated from 3–20A, at up to 250V. They have ETL and CE approvals and are RoHS compliant. OnFilter has recently been awarded US Patent 10,263,591 which covers a“device and method for reduction of electrical noise from pulsed signal devices”. One“unique”version of the filters (model SF20032) combines AC and motor EMI filtering in a single compact package said to solve both bearing damage and AC noise issues. OnFilter designs and manufactures EMI filters to manage interference in a wide range of industries. Its products include filters for power lines, servomotors and VSDs, data filters, and instrumentation for industrial, scientific, medical and other applications. The products are manufactured in the US. www.onfilter.com n TECHNOLOGY Patented drive filters prevent bearing damage and reduce EMI RITTAL HAS developed an adaptor that retrofits its Blue e cooling systems with comms capabilities, allowing them to link up with smart condition- monitoring and IoT systems. The adaptor uses a similar interface to that available for the more recent Blue e+ systems. The new adaptor can be used in a master/slave arrangement to set up conditionmonitoring for up to ten cooling systems. Not only can data be recorded, but efficiency analyses can also be carried out. Amonitoring system can also be set up to detect faults and to issue notifications, thus helping to prevent downtime. The new adapter is compatible with any wall- or roof-mounting Blue e system that uses a Comfort Controller. It can also be used with cooling systems with Nema 3R/4 or 4X classifications. Systems can be configured and commissioned via a built-inWeb server, without any programming. www.rittal.co.uk OnFilter says that its compact, easy-to-install filters modify the damaging sharp edges of PWM drive pulses to offer a maintenance-free answer to the problem of bearing damage Adaptor links older cooling systems to IoT

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