[PLUG-TALK] Motor capacitor

[Pete Lancashire]

sorry was for KL only


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