[RE-wrenches] Diversion load for AC coupled system

[Larry Crutcher, Starlight Solar Power Systems]

"If the current capacity of the diversion controller is exceeded then you want the relay to switch in the big load."

A few questions.
How do I turn on the big load based on current? The controller does not have a current detector, only voltage. Controller on first could still allow over-current if the voltage does not rise another .2 volts. Correct?

Here's a scenario: Sun is up and voltage rises slowly to the diversion controller set point. PWM starts and maintains the voltage. Current continues to increase but the load is keeping the voltage constant until the controller is overloaded. 

It looks like the big load comes on only if power is high enough to overcome the response time of the PWM circuit in the diversion controller thus allowing the voltage pass the .2 volt offset. Also, my thoughts are the hysteresis in the SS relay needs to be broad enough to keep the big load on so it drops out last.

Sorry that I'm not seeing your whole picture yet, David. The operation must be bullet proof. Can you elaborate more?

Larry 


On Nov 30, 2011, at 11:05 AM, David Katz wrote:

> Larry,
> I think you want the PWM controller to start first so the turn on will be smooth.  If the current capacity of the diversion controller is exceeded then you want the relay to switch in the big load.  At that point the diversion controller will back off and pickup the difference.  That is why I suggested the the relay controlled load be 50 to 75% of the pwm diversion load, so that whenever it turns on the pwm controller will be working, too.
> David
>  
> David Katz
> CTO & Founder
> AEE Solar Inc
> P: 707 825-1200
> F: 707 825-1202
> dkatz at aeesolar.com
> www.aeesolar.com
> From: re-wrenches-bounces at lists.re-wrenches.org [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Larry Crutcher, Starlight Solar Power Systems
> Sent: Wednesday, November 30, 2011 8:49 AM
> To: RE-wrenches
> Subject: Re: [RE-wrenches] Diversion load for AC coupled system
>  
> David,
> Ah..I think I see what you are saying. But, don't you mean .2 volts lower than the diversion load? That way there will only be limited current left for the diversion controller to handle. If it is the other way, what stops full current from flowing through the diversion controller if the .2 volts is not reached? Or is .2 volts two close to worry about that?
> 
> Larry Crutcher
> Starlight Solar Power Systems
>  
>  

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