[PLUG-TALK] Motor capacitor

[Pete Lancashire]

show up in McMinnville tomorrow and I'll give you one/two/or ten
that i think we can sub for you ...

-pete





> On Sat, Jul 04, 2009 at 08:21:52AM -0700, Denis Heidtmann wrote:
>> Looking to find a suitable replacement motor capacitor.  The motor is
>> on a chipper (3450 RPM).  I would guess that it is a RUN capacitor but
>> am not sure. It is about 1.5 inches in diameter and 8 inches long.
>> The label information is listed below.  Can anybody here shed some
>> light on this?  Can you tell from the label information that it is
>> indeed a RUN capacitor? (Significant $ difference over a START cap.)
>> If the label does not answer the question, how else might I find out?
>> It looks very difficult to take the motor apart to look for a
>> centrifugal switch.
>>
>> Label:
>> BOSCH
>> 0 670 311 620  MP
>> 40 microFarads  +/- 10%
>> 240V~DB  60 Hz
>> -25/+70 C  HSFNT
>> FZ 5
>> 1029
>> BS 5627  Made in Germany   550 - 8
>>
>> There are also three symbols on the label  One looks like it may
>> represent a motor.  One is a circle containing a + over the letter S.
>> One is a triangle containing the letter V over DE.
>>
>> Knowing some German would likely help.
>
> Well, VDE is for Verband der Elektrotechnik, the German equivalent
> of the IEEE combined with NEC combined with UL, which sets the
> electrical safety standards in Germany.
>
> HSFNT ( see www.nova-elektronik.de/pdf/download.php?...poly%2Fye-ds.pdf )
> describes the climate category:
>
>   H  = -25C
>   S  =  70C
>   F  =  moisture
>   NT =  10K hours
>
> Something with longer lifetime and wider temperature range would
> probably survive better.
>
> I don't know what +S means, but I would guess it means the capacitor
> is suitable as a start capacitor, so it can take a large current for
> a short time into a (temporarily) stalled winding without overheating
> and failing.   I imagine that the capacitor failed because the chipper
> was stalled too long.  The Germans often have problems with stalls;
> consider Field Marshal Paulus at Stalingrad ... :-)
>
> But don't ask me - set aside and hour or so, and go to Conrey Electric
> on SE 7th, a few blocks from Free Geek.  The hour is because there are
> about 4 people working the parts counter, and 2 or 3 people waiting at
> each one, and solving motor problems takes a while.   Conrey focuses
> mostly on motors in HVAC and other building motors, but I've bought
> parts for other motors there, too.  Bring the motor as well as the
> capacitor if you can.
>
> There is a small chance that they (or somebody else) may have some
> kind of retrofit electronic controller that replaces the capacitor
> on the start winding.  A stopped motor generates no "back EMF" and
> looks like a dead short.  The capacitor limits the current.  OTOH,
> the torque is proportional to the current.  So the best way to start
> a motor is with a downconverter that turns line voltage at low
> current into a lower voltage at hellacious current - limited to
> what the windings will withstand, of course.  Newer high efficiency
> motors have electronic controllers that work this way.  But I
> imagine that a retrofit is too individualized and complicated.
>
> Avoid long motor stalls - turn off the motor and clear the jam.  And
> next time, check your victims for large pieces of metal first.  I
> often forget.  Those large 5 Dcell flashlights that the cops carry
> can easily stall a chipper ... :-)
>
> Keith
>
> --
> Keith Lofstrom          keithl at keithl.com         Voice (503)-520-1993
> KLIC --- Keith Lofstrom Integrated Circuits --- "Your Ideas in Silicon"
> Design Contracting in Bipolar and CMOS - Analog, Digital, and Scan ICs
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