April 2007 Variable Voltage Made Easy

Publication Date: 2007
Article Link: Read Article


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SPECIAL NOTICE: Please check each course for verification of approval before purchasing.

This test is based on the article, Variable Voltage Made Easy and counts as 3 contact hours (0.3 CEU) of elevator-industry continuing-education credit. Most courses are approved by NAEC for CET/CAT and NAESAI for QEI and in the following states: Alabama, Arkansas, Florida, Georgia, Illinois, Indiana, Kentucky, Maryland, Mississippi, Missouri, Montana, Oklahoma, Pennsylvania, Vermont, Virginia, Washington, West Virginia, Wisconsin.

Learning Objectives - After reading this article, you should have learned about:

  • the theory of variable-voltage control applied to elevators using the Ward-Leonard system
  • methods of obtaining control of acceleration, deceleration and leveling
  • how to circumvent residual currents
  • the best way to obtain smooth control of elevator motion
  • the use of damping-field and shunt-field motor control
  • the design and operation of a self-excited generator
  • the methods designed to prevent the hoist motor from pulling through the brake
  • what happens when motor load and slip increase
  • resistance and Star-Delta methods of AC-motor starting
  • troubleshooting noises in the driving motor on a motor-generator set
  • causes of sparking in generators and hoist motors
  • how to check a DC machine or motor-generator set for electrical neutral
  • how to trace various variable-voltage problems to parts of the system
  • how to determine the synchronous speed of a motor
  • determining the causes and finding remedies for rough stops

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  5. If you scored 80% or above, you can immediately print your certificate of completion. If you fail the exam, you will be given instructions on how to pay a re-take fee and take the exam again.

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