Copyright 2003-2013 CSM CO.,LTD
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POWER CONTROL SELECTION GUIDE
The SCR power control can deliver electrical power to heaters in several ways: phase angle
fired, zero voltage switched and on/off control.
Phase angle fired controls proportionally turn on a percentage of each power line half cycle.
This gives smooth, infinitely variable application of power to the heaters. It is the most precise
method of control. Phase angle firing can increase heater life
up to seven times depending on
heater type.
Phase angle firing also allows options such as soft start, voltage limit and current
limit. These options are not available with any other means of control.
Zero voltage switching controls proportionally turn on and off each full cycle of the power line.
By varying the number of AC power line cycles, the SCR provides power to the heaters. With a
variable time base, the optimum number of cycles turned on/off is achieved. This method
produces less RFI line noise than phase angle fired SCRs.
On/Off controls function the same way as a mechanical or mercury relay, but with the
advantage of much faster cycle times.
Chart below shows how to best match SCR power control with typical applications.
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