Re: Slow projector fans - Lubrication?

[P3D Dr. George A. Themelis <DrT-3d@xxxxxxxxxxxxxxxxxxxxxxxxxxx>]

Wow!  A thesis on motors by John Roberts!  Photo-3d is a treasure!

>You didn't mention what kind of motor. Low voltage DC? 110VAC?

It is made by Fasco and says Volt: 115, Cycle: 60, Amp.: 1.2.
Oil every 3 months with S.A.E. 20 (no holes or indications where
to put the oil)
    
>Low power AC motors typically are induction-type (no carbon brushes).
>When driven by normal single-phase AC, there's a problem in getting
>enough torque at startup - sort of like getting a foot-pedal powered
>sewing machine going.... 
>The small induction motors I've encountered usually have some asymmetry
>built into the structure to put a sort of "twist" in the electromagnetic
>field, to help get the motor started. This also reduces efficiency and
>causes the motor to run hotter, but it's more compact and cheaper than
>the capacitive start. 

That sounds like it.  The motor feels hot after a while and was
concerned about that.... But then I thought the fan will cool it :-)
(after all that's the motor's job, to keep the projector cool)

>- Does the motor buzz or vibrate during the process of starting up?

No, just turns very slowly at first.

>- After it's been running for a while, if you turn it off for a few
>seconds (long enough to stop completely) and then reapply the power,
>does it start right up?

Yes, right away.

>- Can it be persuaded to start running sooner if you give it a little
>nudge (being very careful)?

No.  It seems that it is delay is inherent to the motor's operation.

>- With no power applied, does the shaft seem to rotate more freely after
> the motor's been running a while?

No.  Seems to be the same.

So doctor, what is the prognosis?  Where should I apply the oil?
Is the slow start an inherent characteristic of these motors?
Some TDC projector fans start right away, others have this delay
but they always start and run well.  This is important for TDC
projector owners.  They are worried that the fans are "slow",
but I can see that they only have a slow start.  After they start
they run at full power (and they are quite powerful)  People
have asked about the lubrication but no one has solved the mystery.

Thanks for the help! -- George Themelis


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