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???
11/27/05 18:32
Modified:
  11/27/05 18:37

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#104231 - Integral Cycle Voltage Control
Responding to: ???'s previous message
Hi,


In the applications where thermal/mechanical constats are of order of seconds, the system power can be controlled by switching the load for whole cycles instead of phase agle control(noisy). the idea is to switch the load on or off for integral number of cycles . First one has to calculate a number N called periodicity so that the system can not notice the absence of the power for those number of mains cycles and N = (m + n)i.e. we turn the load on for n cycles and turn it off for rest of the m cycles. Naturally this depends upon the thermal time constant of your heater. the PWM like duty cyle is defined as

 
                   k = n/N = n/(m + n) 
                        n = number of on cycles 
                        m = number of off cycles  
 



load voltage is given as Vo = Vrms * sqrt(k) and load current = Io = Vo/R.

you will require a Zero Cross Detector to turn the thyristor on synchronously with the mains and a counter to count cycles. The direct gain is, this kind of control puts less noise back on the mains.


Abee



List of 13 messages in thread
TopicAuthorDate
Heating Control System!            01/01/70 00:00      
   PWM            01/01/70 00:00      
      Re:PWM            01/01/70 00:00      
         ZERO volt switching            01/01/70 00:00      
         google fo...........            01/01/70 00:00      
         Integral Cycle Voltage Control            01/01/70 00:00      
            ?            01/01/70 00:00      
         AT89C2051 & MOC3061: Heater control            01/01/70 00:00      
            Thanks Jose,            01/01/70 00:00      
            Incoming water temp ?            01/01/70 00:00      
               Water temperature in SP            01/01/70 00:00      
                  Curiosity            01/01/70 00:00      
                     Curiosity            01/01/70 00:00      

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