MX60 Max Array Voltage? [RE-wrenches]

[Daryl Thayer]

I want to buy a circuit, like a PWM to limit hgh
voltage.  

For MX60 and other things operating near the voltage
limit.  
Hello some of you electronic types.
My very limited electronics does not permit me to
answer this.  In the case of the MX60 and the open
circuit voltage of collector arrays, is it possible to
use the MX60 bypass, diversion load feature to shed
power when the voltage gets to high?  

Second is it possible to build a circuit that uses
pulse width modulation to bypass any of the extra
power to a resistor if the voltage exceeds the
maximum?  This would be handy for inverters also, such
as the sunny boy.   I am considering using this in my
next project that is going to use an MX60, the exact
problem that previous posts have described.  

In my case the peak power voltage is going to be about
110 volts but the open circuit will be almost 200
volts, the peak power current about 10 amps.  I figure
a 20 kHz PWM and a 25 ufd capacitor would keep the
voltage spikes in line.  

I have a similar problem with a SMA install where the
open circuit voltage is above 600 just a little, maybe
700, and of course the peak power is well below 600. 
So I would like a PWM circuit that could limit this
voltage to protect the SMA as I have heard of failures
where the 600 volts is exceeded on open circuit. 

So does anyone know of a person that might design this
circuit for me and how much would it cost?  

Daryl

--- Christopher Freitas  -  OutBack Power
<cfreitas at outbackpower.com> wrote:
> Ray Walters wrote:
> > SOoo, what I'm reading here is that its not quite
> UL listed (which isn't 
> > a problem for this job) but it should work. And if
> conditions are just 
> > right and it does go a volt or 2 over 140 it won't
> matter because there 
> > is plenty of headroom. What is the automatic
> shutoff set at? 145 Voc? 
> 
> Yep - it is set at 145 VDC +/- a little.  
> 
> > What is the ultimate Voc that the transistors
> start blowing? You 
> > mentioned it varies, what is the lowest you've
> seen? Are there other 
> > factors like array current or controller
> temperature? Since the 
> > controller isn't switching, when does it see Voc?
> As it tapers the 
> > finishing charge? Should we put in a dump load to
> spare the controller 
> > at finishing charges?
> 
> The failure voltage of the FETs is not that easy to
> come up with without 
> having a PV array that can be set incrementally. 
> Doing it on a power 
> supply isn't the same - it has a lot of output
> capacitance to "nail" the 
> FET with once it starts going.  A PV array at open
> circuit by definition 
> has no output current until the voltage starts to
> drop - so it is a 
> little different.  
> 
> Technically, when the controller has been shutdown
> the transistors 
> should be able to stand-off 300 vdc or more.  The
> input capacitor 
> however is 160 vdc rated - so don't get too excited.
> 
> 
> >   Which Sharp modules were you using 3 in series?
> The 185 shows a Voc of 
> >   44.9, which would be 6.3 V higher for the series
> total  than the modules 
> >   I was considering. Also, a look at IV curves
> confirms Bill's concern of 
> >   higher Voc at higher irradiance.
> 
> We used the Sharp 165W modules - 43.1 VDC open
> circuit x 3 = 129.3 vdc. 
> 
> The published IV curve data is with the PV cell
> being keeped at 25C or 
> is done with a "flash" type tester - not real world
> conditions.  My 
> experience says it doesn't increase much - but I
> could be wrong or maybe 
> some don't and some do...  



__________________________________
Do you Yahoo!?
SBC Yahoo! DSL - Now only $29.95 per month!
http://sbc.yahoo.com

- - - -
To send a message: RE-wrenches at topica.com

Archive of previous messages: http://www.topica.com/lists/RE-wrenches/

List rules & etiquette: http://www.mrsharkey.com/wrenches/etiquete.htm

Check out participant bios: www.mrsharkey.com/wrenches/index.html

Hosted by Home Power magazine

Moderator: michael.welch at homepower.com
==^================================================================
This email was sent to: michael_welch at sbcglobal.net

EASY UNSUBSCRIBE click here: http://topica.com/u/?bz8Qcs.bz9JC9.bWljaGFl
Or send an email to: RE-wrenches-unsubscribe at topica.com

TOPICA - Start your own email discussion group. FREE!
http://www.topica.com/partner/tag02/create/index2.html
==^================================================================