On 2017-07-12, wrote:
On Tuesday, July 11, 2017 at 5:40:08 PM UTC-4, Dave, I can't do that wrote:


What can be done to alleviate this momentary voltage drop?

Thanks

Do you have a way to measure the current drawn by the motor? If you
can measure the current , you can put some oil filled capacitors in
parallel with the motor and find a combination that minimises the
current. -In other words correct the power factor. This may or may not
be enough to reduce the momentary voltage drop to a level that is
acceptable. But will help.

The primary problem is while the start winding is engaged, so it
would have to be added to the internal wiring in parallel with the start
winding. Add a second "bump" to house an oil-filled AC-rated capacitor.
(And *don't* use motor starting caps -- they are only for short power
application -- and they might stretch the starting time enough to be a
problem both for the starting cap and the phase correction cap.

The best way to tune that value would be with the run winding
disconnected, and something keeping the motor from turning -- and just
short tests each time to keep the start winding from overheating.

Yes, it is easier to simply compensate the run winding, but that
won't eliminate the voltage sag on starting.

Capacitors can be found in junk microwave ovens.

Yep -- or as run caps for motors for squirrel cage blowers in
HVAC units.

Or -- you can get one of the universal substitute run caps for
the AC compressor -- Turbo 200 from Amrad Engineering. It has six
different values of capacitors, connected together at a central common
terminal, and jumpers (push-on connectors) to add them in parallel. The
values, between them, offer a fairly wide range of possible values.
Cap values add in parallel, while resistor values add in series.
Anyway, this gives you a single device to use to try a number of values.

Enjoy,
DoN.

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