Next message: Lew Hodgett: "lv-ab: Re: Worthless Circuitbreakers"
On Mon, 01 Sep 2003 10:57:24 -0400 "ahmet erkan" <>
writes:
>I agree with Lew, "This ain't rocket science" however I disagree with
>every
>other conclusion. (Hoping we could disagree and still remain
>friendly.)
>
>IMHO, if we are trying to establish a certain circuit breaker's
>reliability
>to trip and not damage itself, this has been accomplished. (Occasional
>
>tripping under overload for a test period of over a decade tells me
>this CB
>can deal with the stresses it is subjected to in this application.)
>
>If we are trying to figure out why Norm's CB's trip, the current
>carying
>capability of the feeder may play a different role for the Windlass vs
>the
>Inverter. The Inverter typically has a feedback loop that tries to
>maintain
>constant output voltage when the input voltage sags, therefore the
>output
>power remains constant. As an example, if the feeder wires to the
>inverter
>drop 10% of the DC bus voltage, the inverter will require about 10%
>more
>input current to maintain the output voltage, thus the CB current will
>
>increase by 10% getting it closer to tripping. (Bottom line : Use
>heavier
>wires and the same CB may stop tripping.)
>On the other hand the Windlass may not have a feedback loop, thus it's
>input
>current may decrease when the input voltage decreases, thus causing
>the
>circuit breaker current to also decrease. (Bottom line : Use heavier
>wires
>and the same CB may trip even faster)
>
>The manufacturer of the Inverter needs to specify the maximum current
>the
>device will cause in the input wires, during all possible operating
>conditions including overload. We the user should use a circuit
>breaker that
>is rated a little higher than the specified maximum. As an
>alternative, we
>can install an interlock system that will disable other loads when a
>certain
>load is turned on, thus prevent the overload from ever taking place.
>The manufacturer of the windlass needs to specify it's locked rotor
>current
>vs. input voltage and a CB should be used that is rated higher than
>the
>specified maximum current. If more effort is needed from the Windlass,
>
>heavier wiring and CB needs to be used.
>
>IMHO it is an undesirable and potentially unsafe situation to rely on
>
>mechanical contacts interrupting large currents on a regular basis.
>The
>manufacturer of the windlass should provide some form of electronic
>sensing
>and maybe timing of the overload condition and either sounding an
>alarm or
>overriding the operator controls. (For mission critical equipment such
>as a
>windlass there should also be an override for the protection circuit
>that
>can be activated in the heat of a battle.)
>
>Due to manufacturer's providing us with a lot of BS and inferior
>products,
>if the frequent CB tripping is to be employed as an economical means
>of
>protection, IMHO there should be heavy bare wires connected to the CB
>
>terminals, the other ends should be bolted to large busbars with
>sufficient
>surface area, serving as heatsinks. The insulated wiring can route the
>
>current safely from the bussbar to the loads. If the CB contacts have
>
>carbonized over the years of hard use and one day they decide to begin
>
>arcing and dissipating large amounts of heat, the fire will be
>contained in
>a non flammable CB enclosure and the heat will not conduct out of it
>through
>the wiring. If there is nothing to burn such as wiring insulation the
>CB
>will eventually melt up enough metal at it's contacts and the circuit
>will
>open. Hot wires with burning insulation and no means to shut-off the
>power
>is indeed a nightmare and I would not want any sailor to be subjected
>to it.
>
>Have a good Labor day weekend,
>
>
>Ahmet
>
>
>
>
>>From: Lew Hodgett <>
>>To:
>>Subject: lv-ab: Re: Worthless Circuitbreakers
>>Date: Sun, 31 Aug 2003 15:24:28 -0700
>>
>> writes:
>>
>> >Lew,
>> >
>> >I said very clearly in my message:
>> >
>> >Quote
>> >The fact is that both of these breakers have tripped when they
>should
>> >have,
>> >with no apparent ill effects. The house buss breaker has tripped
>> >several times
>> >when I have called upon my anchor windlass to maximum effort, and
>the
>> >breaker
>> >feeding the Trace inverter regularly trips when someone tries to
>> >operate two
>> >high load galley appliances at the same time. These two breakers
>have
>> >been in
>> >operation for almost a decade and seem to work just fine.
>> >Unquote
>>
>>The above indicates the following:
>>
>>1) If the feeder supplying the windlass has been properly sized, then
>the
>>c'bkr tripping represents a nuisance trip which is not within the
>scope
>>of proper operation.
>>
>>2) If the c'bkr is the proper size to protect the feeder supplying
>the
>>windlass, then the feeder is undersized for the application.
>>
>>In any event, there is a problem.
>>
>>Similar logic applies to the Trace inverter; however, if the output
>of
>>the inverter itself is placed in an overload condition, then there is
>a
>>basic circuit design problem.
>>
>>As the popular saying puts it, "This ain't rocket science".
>>
>>
>>Lew
>>
>>S/A: Challenge (Under Construction in the Southland)
>>
>>There are no problems, only varying degrees of Challenging
>Opportunity.
>>
>>
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