Design World – August 2019

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To address the latest developments in frequency-controlled motors,

variable-frequency drives (VFDs) show a clear trend: more compact design

with the same or higher power with extremely high switching accuracy of the

frequency converters.

As a result, in the future the user must not only pay attention to the right

number of conductors and AWG size combinations, but also to the electrical

characteristics of the motor or servo cables. For that reason, igus has been

developing and testing materials made of high-performance polymers for years.

Cable theory describes an electric cable as an electrical quadrupole, comprised

of inductance, capacitance, resistance and dissipation factor. Every electric cable

has a certain inductance, capacitance and ohmic resistance depending on its

structure and the materials used. The purely ohmic resistance in an industrial

environment depends mainly on the conductivity of the conductor material

(usually copper), its AWG size and length, while the capacitive values are strongly

dependent on the insulating material.

Thus, two identical cables with identical conductor structures of the same

length and AWG size with different insulation materials have completely different

capacitive specifications.

42 August 2019 http://www.designworldonline.com DESIGN WORLD

The importance of insulation for

safe, failure-free operation of VFDs

Connector Notes

Edited by Mary Gannon • Senior Editor

Test shows heat propagating

into the cable

Connector Notes 8-19_Vs4.LL MG.indd 42 8/5/19 11:19 AM