Inverter Problems
Snip from Arild: "Using the rotary switch to break load current is bad
practice and leads to contact arcing. This in turn leads to burnt and high
resistance contacts which will eventually give you excessive voltage drop."
I have an Onan Rotary Switch for switching the Inverter to Shore Power and
visa versa. It has 4 positions. Push and turn through them - the two middle
positions through which the switch passes I think disconnect the system and
are unmarked. I assume this overcomes the problem you mention?
Ron Barr
Lady Brookhaven Hatteras LRC
Newport RI
From: "ron barr" rwhb@msn.com
Snip from Arild: "Using the rotary switch to break load current is bad
practice and leads to contact arcing. >
I have an Onan Rotary Switch for switching the Inverter to Shore Power and
visa versa. It has 4 positions. Push and turn through them - the two
middle
positions through which the switch passes I think disconnect the system
and
are unmarked. I assume this overcomes the problem you mention? (endsnip)
Well, obviously I'm not Arild, but I don't think that does anything to
overcome the problem. The problem is to make or break the contact with a
large load on them. In your case, it will arc on the one set of contacts
when it breaks the connection, and then arc again when it makes the next set
of contacts with the same load still present. You're still going to end up
with a rotary switch that looks like that one that Keith has a pic of on his
website.
While I realize that breakers are not "switches", I still turn off all
breakers before I flip my rotary (shore / off / genset) switch or unplug my
shore power cords. It's easy to see the results of unplugging a shore power
cord under load. Just look at the end of the male plug and see the black,
burnt ends there. That's what the contacts on the inside of your rotary
switch will look like.
Brent Hodges
-----Original Message-----
From: Brent Hodges
While I realize that breakers are not "switches",
REPLY
This is a sentiment mentioned on the list several times in the past week.
One of the biggests supplier of marine type circuit breaker/switch is
Carlingswitch a company that started in the business making just ordinary
switches.
The modern marine grade device is both switch and circuit breaker. I seem to
recall seeing a statistic somewhere that one of these can withstand full
overload disconnects for at least 10,000 cycels and many more as the load
current lessens.
Inside the breaker/switch you will find an intricate mechanical mechanism
consisting of a set of contacts; and a compound lever and fins surrounding
the area of the contacts. These fins are for cooling the arc so it
extinguishes faster. The lever is connected to a hydraulic piston ana
cylinder containing silicon fluid all of which is surrounded by a magnetic
coil. Al of this is almost as precise as a swiss watch movement.
The closing action of the contacts is designed to impart a slight sideways
movement to create a wiping action of the contacts. This will wipe the
carbon buildup on the contact face to prolong the servioe life.
Now compare this intricate mechanism with a typical appliance switch sold by
the millions in lamps, fans, small motors, etc. No comparison! The breaker
is far superior in terms of long life capability.
It is doubtful you would ever operate any of the breaker on board as many as
10,000 times, never mind a million.
The modern marine breaker/ switch is a compact solution to the problem of
providing over current protection to a circuit as well as a switch control
point in a simgle device that require less wall area than a normal household
switch which will not last nearly as long.
As for Brent Hodges comment about arcing in the selector switch for Onan;
he is spot on.
Arild
intrersting... thank you for the clarification, I 'm always happy to learn
something new ! :-)
pascal
----- Original Message -----
From: "Arild Jensen" elnav@telus.net
To: "Brent Hodges" vbhodges@cableone.net; "ron barr" rwhb@msn.com;
trawlers-and-trawlering@lists.samurai.com
Sent: Wednesday, May 31, 2006 10:06 AM
Subject: T&T: Urban myth buster time. was inverter problem
-----Original Message-----
From: Brent Hodges
While I realize that breakers are not "switches",
REPLY
This is a sentiment mentioned on the list several times in the past week.
One of the biggests supplier of marine type circuit breaker/switch is
Carlingswitch a company that started in the business making just ordinary
switches.
The modern marine grade device is both switch and circuit breaker. I seem
to
recall seeing a statistic somewhere that one of these can withstand full
overload disconnects for at least 10,000 cycels and many more as the load
current lessens.
Inside the breaker/switch you will find an intricate mechanical mechanism
consisting of a set of contacts; and a compound lever and fins surrounding
the area of the contacts. These fins are for cooling the arc so it
extinguishes faster. The lever is connected to a hydraulic piston ana
cylinder containing silicon fluid all of which is surrounded by a
magnetic
coil. Al of this is almost as precise as a swiss watch movement.
The closing action of the contacts is designed to impart a slight sideways
movement to create a wiping action of the contacts. This will wipe the
carbon buildup on the contact face to prolong the servioe life.
Now compare this intricate mechanism with a typical appliance switch sold
by
the millions in lamps, fans, small motors, etc. No comparison! The
breaker
is far superior in terms of long life capability.
It is doubtful you would ever operate any of the breaker on board as many
as
10,000 times, never mind a million.
The modern marine breaker/ switch is a compact solution to the problem of
providing over current protection to a circuit as well as a switch control
point in a simgle device that require less wall area than a normal
household
switch which will not last nearly as long.
As for Brent Hodges comment about arcing in the selector switch for Onan;
he is spot on.
Arild
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My transfer switch is 26 years old and still ticking with no special
treatment...
Regards....
Phil Rosch
Old Harbor Consulting
M/V "Curmudgeon" MT44 TC
Currently lying Bond Creek, NC