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???
09/21/10 07:24
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 		 #178617 - Again: Power? Voltage? Current?
Responding to: ???'s previous message
Kiran V. Sutar said:
the controller gives 30% of the Mains Voltage (sic?) to the Heater. This is measured and verified.

Again, are you sure that it's voltage - how, exactly, have you verified this?


I need to control the voltage and the current to the heater.

For a resistive heater, the voltage & current are directly linked by Ohm's Law - so, if you control one, you are controlling the other!

The only issue with this is that the resistance is significantly different when cold and when hot - hence you need the "soft start" to cope with the special case of the low cold resistance.

You don't really need a detailed control of the current - just to limit its maximum value!

List of 41 messages in thread
TopicAuthorDate
What is the reason for Heater blowing.            01/01/70 00:00      
   Hof often/how we?            01/01/70 00:00      
      Some more information...            01/01/70 00:00      
   continuous rating            01/01/70 00:00      
      This could be the reason...            01/01/70 00:00      
   Way too much current...            01/01/70 00:00      
      Some more information required...            01/01/70 00:00      
   do you have hysteresis in your control?            01/01/70 00:00      
      No there is no hysteresis.            01/01/70 00:00      
         Four pulses?            01/01/70 00:00      
            The Heaters are failing, electronics is OK.            01/01/70 00:00      
               Why Pulses?            01/01/70 00:00      
                  I will do just that...            01/01/70 00:00      
                     Processor must know about zero-crossings            01/01/70 00:00      
               ??            01/01/70 00:00      
                  soft start            01/01/70 00:00      
                     Soft Start            01/01/70 00:00      
                        an easy and interesting check            01/01/70 00:00      
                           Soft start, again...            01/01/70 00:00      
                  Yes these heaters need Soft start            01/01/70 00:00      
                     Again: Power? Voltage? Current?            01/01/70 00:00      
                        Avoid driving gate all the way to next zero crossing            01/01/70 00:00      
                           Crest factor/power factor correction            01/01/70 00:00      
                     Phase angle control...            01/01/70 00:00      
                        I agree with you.            01/01/70 00:00      
                           Good luck!            01/01/70 00:00      
                           are all heating coils the same ?            01/01/70 00:00      
                           There You Go            01/01/70 00:00      
         re the possible need for hysteresis            01/01/70 00:00      
         Power? Voltage? Current?            01/01/70 00:00      
   Alternate Heating Control Algorithm            01/01/70 00:00      
      Some more clarification...            01/01/70 00:00      
         Voltage - or power? [ed]            01/01/70 00:00      
   The other controllers            01/01/70 00:00      
   Thanks All members.            01/01/70 00:00      
   just suggest..            01/01/70 00:00      
      Reply to JecksonS Ben            01/01/70 00:00      
         Good point!            01/01/70 00:00      
            supposed to            01/01/70 00:00      
         opto isolated triac            01/01/70 00:00      
   My solution            01/01/70 00:00      

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