Rockwell-automation System Design for the Control of Electrical Noise Manual de usuario descargar pdf (Pagina 47)

Publication GMC-RM001A-EN-P — July 2001

Chapter

Filtering Noise

Chapter Objectives

This chapter describes how low-pass filters and ferrite sleeves can

reduce electrical noise coupling. This chapter covers the following

topics:

• Understanding the filtering concept

• Filter performance

• Ultrasonic transducers

• AC line filters

Understanding the Filtering

Concept

If sources and victims are connected by wiring, you can prevent noise

coupling by filtering. Low-pass filters attenuate high frequency noise

without affecting the low frequency signals.

Commercial AC Line Filters for Low Voltage Circuits

Provided that motor cable lengths are short, less than 20 m (60 ft),

commercial AC line filters work well in low voltage circuits. Two-stage

types are preferred.

If motor cable lengths are long, the natural ringing frequency is

typically at too low a frequency (below 300k Hz) to be attenuated by

commercial AC line filters. To determine if your cables are long, refer

to the section Installing Long Motor Cables in Appendix A.

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Rockwell-automation System Design for the Control of Electrical Noise Manual de usuario Pagina 47