[RE-wrenches] SB 240 - No Neutral Sense Conductor

[Bill Brooks]

Mark,

 

There are many inverters that do not have a neutral-just not many
single-phase inverters. Since all inverters must have at least an equipment
ground, the phases can be compared with ground. The testing standard covers
what is required. If neutral-ground bond is lost, it will show up in a bad
voltage phase-to-ground.

 

Since utility-interactive (U-I) inverters just inject current when the
utility voltage is in proper range, our inverters do not produce a separate
voltage. The only problems that our inverters can cause is a slightly raised
voltage due to current flow at the point of connection. Also, a much less
likely but current concern in Hawaii is temporary overvoltage. As the
utility voltage goes to zero in an outage, a U-I inverter must quickly clamp
its current or the voltage at the inverter terminals (and potentially the
house service) could momentarily go above nominal voltage. Generally, this
is not a problem since an inverter that does not act quickly enough will
damage itself.

 

Bill.

 

Bill Brooks, PE

Principal

Brooks Engineering

3949 Joslin Lane

Vacaville, CA 95688

707-332-0761 (office and mobile)

bill at brooksolar.com (email)

www.brooksolar.com (web)

 

 

 

From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Mark Frye
Sent: Thursday, December 19, 2013 8:10 AM
To: RE-wrenches
Subject: [RE-wrenches] SB 240 - No Neutral Sense Conductor

 

Folks,

I was looking at the SMA micro inverter and notice only connections for L1,
L2 and earth. I thought all grid tied inverters needed a neutral sense
conductor to monitor for phase loss.

Any ideas?

Mark Frye



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