10 Sep
2014
10 Sep
'14
1:35 a.m.
On Wed, 3 Sep 2014, Chuck Guzis wrote:
On 09/03/2014 12:50 PM, Paul Koning wrote:
Fewer and fewer capacitor manufacturers make non-polarized electrolytics
now, just like what has happened with the ultra-low ESR types required for
certain computer motherboards. Nichicon for example has discontinued most
of their non-polarized electrolytics, except for their VP and EP radial
types. Even those are often not stocked by distributors (or if they are,
they have a very limited selection of the values Nichicon makes).
None of these small non-polarized electrolytics are suitable for motor
start/run applications though, their ripple current rating is just far to
low. I have an antenna rotator with a 24V motor that I've been completely
unable to find a replacement motor run capacitor that will fit in the
controller's cabinet. The original looks to be a wax-paper type, but it is
only rated for 50VAC. The best option I've come up with so far (not yet
installed) is a pair of high ripple current rated polarized electrolytics
back to back in series.
?Asynchronous??
Run caps are found in AC induction motors fed by a single phase power
source, whether electronic or not. If you have an actual multi-phase
power source (3 phase mains or a multi-phase motor controller) then
there is no run cap.
Are nonpolar electrolytics uncommon? Seems to me that one major use is
in audio crossovers for the "make it louder" crowd.
Here's a 100 uF, 100V one from All Electronics for about a buck and a
half.
http://www.allelectronics.com/make-a-store/item/nc-100/100uf-100v-non-polar…
They're in most distributors' catalogs--just look for "non polar
capacitor.