[RE-wrenches] Cable tray

[Exeltech]

John,

My reply didn't deal with anything except specific hardware (per Chris'
mention in his original post), his musings that "he suspects it does not
cost more" to make that leap, and the actual impact on cost for migrating
that hardware from 600Vdc to 1000Vdc.

Nothing was mentioned either by Chris or by me related to control
electronics, power ratings, or power loss.


To Chris' statement: 

BEGIN QUOTE:
I suspect it does not cost more to make 1000V wire than 600V, similarly disconnects, fuses, fuse holders and connectors.
END QUOTE.


All things being equal:

1000V wire in the same gauge as 600V wire will be more expensive than the 600V wire.
If you wish to downsize the conductor, the cost of the metal is likely more expensive
than the insulation, and this is a potential win .. but conductor size wasn't mentioned.
 
1000V disconnects for a given current are going to be more expensive than  600V
disconnects.

1000V rated fuses are going to be more expensive than 600V for a given current.

1000V fuse holders require larger spacings than 600V, so they too are more money.

1000V connectors require larger creepage and clearances than do 600V parts.
This means they're larger for a given number of contacts and current, thus
more $$$ -- even if just slightly more.  Still more.

This is not to say migrating to 1000V won't happen.  It will, and it is.  Yes, it's
more common in Europe.  Sometimes the USA doesn't lead, but follows.
This is one of those instances.

And to your point:
 
John Berdner Wrote:
> Although the spacing between the high voltage dc components increases,
> the power of the device also increases and the losses decrease.

Referencing I^2 R loss .. yes.  Passive resistive devices at a higher voltage
and lower current do have less loss than their lower-voltage cousins, (again,
all things being equal, but that doesn't mean they're less expensive than
their lower-voltage counterpart.

It's simply not possible to make a blanket statement and have it cover
everything correctly.


And to your additional point:

> Small gauge PV wire is already available from multiple sources with
> 1000 and 2000 V  ratings for a small premium over 600 V wire.

"... for a small premium over 600V wire."

You admit the wire is more expensive (even if at present).  Still, it's more $.
Will it stay that way?  Likely not, but for NOW .. it's more expensive.


Now then .. taking your comment in context:

BEGIN QUOTE:
> Example: The control electronics and all ac output circuitry remain the same.
> 
> Although the spacing between the high voltage dc components increases,
> the power of the device also increases and the losses decrease.
> 
> The result is that the product >>might be a little larger<< but its power rating
> will be higher and it will likely be more efficient.

This infers reference to the efficiency of switching electronics.  If so, your
statement is incorrect.

Let's consider the solid state switches in an inverter, whether they be
MOSFETs, IGBTs, GaN, etc.

With the devices presently on the market, switching loss goes UP as
the voltage increases.

This will likely change at some future point with new product discoveries,
but for now .. given the parts we have to work with, switching losses are
greater in the higher voltage parts.  I know this flies in the face of common
sense to non-engineers, but it's fact.

If you wish an alternate resource of verification on this, I suggest you
check with anyone else with considerable expertise in the design of
switchmode power supplies.  If my 41 years as a design engineer isn't
adequate here, boB and/or Robin at at Midnight Solar would be an
excellent starting point.  I can point you toward a number of others
who are equally qualified.  Our industry (and even perhaps the Wrench
board) has others as well.

Ultimately .. will higher voltage systems be lower cost per watt overall?
This remains to be seen.  My instincts say it will --- in some circumstances.

An advantage the increased voltage offers (beyond potentially less power loss
in conductors), is the ability to create inverters for 277/480 and beyond.  This
helps by eliminating a transformer, which IS an efficiency loss and added cost
element.  Will 1000Vdc be a win for [say] 120V/240V installations.  Likely not.


As John did point out .. the entire system must be considered.  That goes without
saying.  Whether higher voltage is a win or not depends on the system.  It may be
in some cases, and not in others.  Chris mentioned only specific aspects of the
BOS hardware -- which I addressed.


Regards to all,


Dan Lepinski
Sr. Engineer
Exeltech / Exeltech Solar Products




--- On Sun, 3/31/13, John Berdner <John.Berdner at solaredge.com> wrote:

From: John Berdner <John.Berdner at solaredge.com>
Subject: Re: [RE-wrenches] Cable tray
To: "RE-wrenches" <re-wrenches at lists.re-wrenches.org>
Date: Sunday, March 31, 2013, 1:08 PM



Dan:  I have to disagree with your statement regarding costs and voltage.While clearance and creepage distances increase at 1000V this makes only some things larger. Example: The control electronics and all ac output circuitry remain the same.Although the spacing between the high voltage dc components increases, the power of the device also increases and the losses decrease.The result is that the product >>might be a little larger<< but its power rating will be higher and it will likely be more efficient.For a given current level the higher voltage might increase the unit price slightly but the $/Watt will almost certainly decrease.Conversely if power is held constant the current will be lower and so the product may in fact be cheaper that a 600V product of the same power rating.  Once we get past the unit price for components there is no doubt that system costs for 1000V are significantly lower than for 600V.  Let’s review…  Ohms law:P=V*I, so
 for a given power level voltage and current are inversely linked linearly – if the voltage increases the current decreases.P=I^2 * R, so for a given power level, increasing the voltage decreases the current and decreases the losses by square of the change.1000/600 = 1.667 => P_loss= 1.6667^2, so for a given power level and given piece of wire, the losses are 2.777 times lower at 1000V than at 600V.  Wire and Ampacity: The ampacity of a wire is based on current not voltage Higher voltages mean 1.667 times more power on a given piece of wire in a given conduit (yes the conduit might need to be bigger due to fill factor – it depends).
Another way of saying this is 1000 Vdc gives you a 40% reduction in wiring costs for a given power level compared to 600Vdc.Small gauge PV wire is already available from multiple sources with 1000 and 2000 V  ratings for a small premium over 600 V wire.Why ? - Current = conductive materials = expensive.  Voltage = insulating materials = inexpensive.Larger gauge PV wire and USE-2 is still a bit hard to find but are both available in commonly used PV sizes from multiple sources  Fuses and Combiners:kW per string is a key cost metric for installed BOS costs and more is better.Fundamentally, series trumps parallel every time.Higher voltages = longer strings = more power per string = less strings, fuses and holders (combiner inputs).1000 V string fuses / holders are available from multiple sources and are competitive with 600V counterparts.  Switches:1000V switchgear cost is still lagging in the US but we are starting to see more reasonably priced
 equipment on the horizon.  Summary: 1000V PV is well proven outside the US.In the US the tide is turning and we are rapidly headed to 1000V commercial systems. The Codes and Standards are already in place and we are beginning to see reasonably priced 1000 Vdc rated components.1000Vdc Listed Modules, 1000/2000Vdc UL 4703 PV wire, Listed 1000Vdc string fuses and holders, Listed 1000Vdc inverters are all available today.  I believe 600Vdc commercial and utility scale systems will rapidly become uncompetitive and, within a few years, the exception rather than the rule.  Best Regards,  John BerdnerGeneral Manager, North AmericaSolarEdge Technologies, Inc.
  From: re-wrenches-bounces at lists.re-wrenches.org [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Exeltech
Sent: Sunday, March 31, 2013 9:10 AM
To: RE-wrenches
Subject: Re: [RE-wrenches] Cable tray  Hello Chris,

>From a manufacturer's perspective .. you're incorrect on all assumptions.
(Sorry.)

It costs more to make higher-voltage anythings.

Higher voltage means: Clearance / creepage distances are larger (thus bigger parts or products).  Insulation must be thicker (or have a higher dielectric rating).  This results in more rigorous (consequently more expensive) UL testing.  Etc. All adds up.

Dan


--- On Sun, 3/31/13, Chris Mason <cometenergysystems at gmail.com> wrote:
From: Chris Mason <cometenergysystems at gmail.com>
Subject: Re: [RE-wrenches] Cable tray
To: "RE-wrenches" <re-wrenches at lists.re-wrenches.org>
Date: Sunday, March 31, 2013, 8:21 AMAs we see more 1000V installations, chances are that 600V rated equipment will find its way into installations it is not rated for. To avoid problems and so we don't need two SKUs and lots more inventory, the manufacturers need to move all their product to 1000V ratings. I suspect it does not cost more to make 1000V wire than 600V, similarly disconnects, fuses, fuse holders and connectors.   
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org/attachments/20130331/14f341a3/attachment-0003.html>