SAIMC


SAIMC: Johannesburg branch

June 2018 SAIMC

At the last technology evening Eric Carter from turboTRAIN hosted and gave a presentation on ‘Avoiding pitfalls with variable speed drives’ on the premise that “If I understand it, I can work with it”.

Ann de Beer presents Eric Carter with the SAIMC presenter’s certificate.
Ann de Beer presents Eric Carter with the SAIMC presenter’s certificate.

Variable Speed Drives (VSDs) control the speed of machinery. Many industrial processes, such as assembly lines, must operate at different speeds for different products. Where process conditions demand adjustment of the flow from a pump, fan or conveyor belt, varying the speed of the drive may save energy or have more precise control as compared with other techniques. Although VSDs are promoted as a perfect solution with some wonderful advantages, they do also have drawbacks such as low speed torque, response to sudden load changes and low speed cooling.

Other topics covered by Eric included:

• Achieving vector control with encoder or via sensorless

• Control loops for DC motors

• Supply-side problems

• Notching

• Harmonics

• Pulse width modulation

• Effect of inductors

• Maximum cable lengths with reactors

• Switching pulse overshoot

• Electromagnetic compatibility (EMC)

• Motor braking (dynamic and DC injection)

• Unexpected VSD trips

Understanding the cause of these problems can help mitigate the problems and move towards providing solutions. The SAIMC would like to thank Eric Carter for his informative and well received presentation.



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