PV Inverters module strings [RE-wrenches]

[Kent Sheldon]

You got it, mostly.

The CEC doesn't have anything to do with the 600V limit. CEC is just
following the NEC/IEEE. NEC has special requirements for anything over
600Vdc (which none of us would want to deal with, especially on residences).
Also, electrical equipment is typically rated at 600V. Anything over that
would require higher voltage ratings, which dramatically increase size of
components and cost.

You can design the converter to accept lower DC voltages, but this requires
an additional conversion stage, which adds costs and reduces efficiencies.
We can also lower the output voltage of the inverter, which increases AC
currents, adds component costs, slight rise in conductance losses, and puts
us in the very customer transformer arena. Every year there seems to be
worse fill factor PV available, so the low end of our DC window keeps
getting tested. But, so far, we have been able to work with most designs.
There are a few thin film designs out there which will want to track lower
than 300Vdc on hot days, while pushing the 600Voc/NEC limit on cold days.
But most people realize that this will only happen on particularly hot days,
which only happens occasionally throughout the year, and they are OK with
the occasional reduced energy capture. I'm sure there are some regional
exceptions. Hopefully, our new lower DC limit software will address this
issue.

Kent Sheldon
Product Manager - Photovoltaic Engineering Group
Xantrex/Trace Technologies Inc.
925 245 5463/925 245 1022 Fax
kentsheldon at tracetec.com  www.xantrex.com


-----Original Message-----
From: Eric Smiley [mailto:Eric_Smiley at bcit.ca]
Sent: Wednesday, March 28, 2001 3:47 PM
To: RE-wrenches at topica.com
Subject: RE: PV Inverters module strings [RE-wrenches]



Thanks to Bill and Kent.

If I understand this correctly:
a) The upper limit of 600 V max Voc is fixed by the NEC/CEC.
b) The lower limit is fixed by the line voltage.
c) There isn't a thing we can do about this.

We just need PV modules with a good Fill Factor so that they don't
wander below the MPPT window during  high temperatures, and don't exceed
600 V at low temperatures.


----------------------------------------------------------------------
Eric Smiley
Project Leader - BCIT Technology Centre
Photovoltaic Energy Applied Research Lab (PEARL) - BCIT
ph: (604)432-8657 www.bcit.ca/~tc/pearl/index.htm

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

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

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

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

To check out the other RE-Wrench participants:
 www.mrsharkey.com/wrenches/index.html

Hosted by Home Power magazine:
 www.homepower.com

For info contact list moderator by email:
 michael.welch at homepower.com

____________________________________________________________
T O P I C A  -- Learn More. Surf Less.
Newsletters, Tips and Discussions on Topics You Choose.
http://www.topica.com/partner/tag01


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

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

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

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

To check out the other RE-Wrench participants:
 www.mrsharkey.com/wrenches/index.html

Hosted by Home Power magazine: 
 www.homepower.com

For info contact list moderator by email:
 michael.welch at homepower.com

____________________________________________________________
T O P I C A  -- Learn More. Surf Less. 
Newsletters, Tips and Discussions on Topics You Choose.
http://www.topica.com/partner/tag01