Array Voc > 140V for MX-60 [RE-wrenches]

[Jim Easton]

We looked into this some years ago.  One of our thoughts was to use zener
diodes across the array.  You would have to look carefully at the IV curve
in cold weather to make sure you had enough zener power capacity.  For more
power capacity you can put zeners in series -- do not try to put them in
parallel.

Jim Easton PE
Alternative Energy Technologies
www.altenertec.com
CSL: 852243
9465-B Mission Park Place
Santee, CA 92071
Tel: 619-262-8800
Fax: 619-562-8811
Cell: 858-527-0240

-----Original Message-----
From: Kelly Larson [mailto:solarwrench at asis.com] 
Sent: Thursday, January 18, 2007 10:02 AM
To: RE-wrenches at topica.com
Subject: Array Voc > 140V for MX-60 [RE-wrenches]


Fellow Wrenches,

Has anyone figured out a kluge for the "Voc too high in the morning" 
problem on the input from the array to the MX-60?  I have run into two 
systems (not designed by me) where the MX-60 doesn't connect until later 
in the morning on cold days due to this.

On one, the array is mounted on a 2 story home under the ridge cap, 
which at this point is not accessible, (because of weather), so I can't 
just go around the last module in the strings.  I figure some 
diode/relay/electronic thingy.

So I am looking to drop about 10 - 15V, (from 150Voc to 140V, or better, 
135V), with 20A max current

Thank you in advance for any ideas,
Kelly

Kelly Larson
BSEE, Ca C-10 #868189, Energy Educator


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