grossman@bbn.com (Martin Grossman) (05/03/89)
I need to get a sync motor running and need help
The motor face place reads:
synchronous
voltage 120
frequency 60Hz
1 phase
torque 90inch ounces
capacitor .85mfd
it has 3 leads.
I measured the resitance on the leads as follows:
black blue red
o o o
| | |
--- 750 ohms -- -- 750 ohms ---
| |
------------1500 ohms----------
Question:
which leads do I hookup the 120V ?
which leads do I hookup the capacitor ?
what type of capacitor (.85mfd) do I use ?
what should the voltage rating of the capacitor be ?
PS
1) This is a motor used for a telescope clock drive.
2) The motor has a built in gearing so shaft rotates 2RPM
respond via email to:
grossman@bbn.com
or
uunet!bbn!grossmantomb@hplsla.HP.COM (Tom Bruhns) (05/05/89)
> grossman@bbn.com (Martin Grossman) writes: / 8:17 am May 3, 1989 / > >I need to get a sync motor running and need help > >The motor face place reads: > > synchronous > voltage 120 > frequency 60Hz > 1 phase > torque 90inch ounces > capacitor .85mfd > > > it has 3 leads. > > I measured the resitance on the leads as follows: > > black blue red > o o o > | | | > --- 750 ohms -- -- 750 ohms --- > | | > ------------1500 ohms---------- > > >Question: > which leads do I hookup the 120V ? > which leads do I hookup the capacitor ? Blue to one side of 120VAC line. Other side of line to both the red lead and one side of the capacitor. Other side of cap to black. That is, black in series with capacitor, to red; red and blue to line. If it runs backwards from what you want, put the cap in series with the red instead of with the black, so black goes directly to the line and red is thru the cap. Note that this is simply connecting the cap between black and red, and connecting line to either black or red (other side to blue). > what type of capacitor (.85mfd) do I use ? If you can possibly find one, it should be rated for AC motor run service; I don't recall what's standard, but I think something like "150 VAC". Usually the exact value isn't toooo critical, and 1.0 uF would likely be OK, but try some place like Grainger -- they very well may have such a beast. You can use a plastic film DC-rated cap, too, but you may have trouble with failures due to the fairly high AC current in the cap. I wouldn't expect the failures to be spectacular, so feel free to try if it comes down to that. Should be rated at at _LEAST_ 200 VDC. I'd look for one with low series inductance, simply because that probably also means low effective series resistance. > what should the voltage rating of the capacitor be ? (see above) I'd also fuse the circuit. I'd try a 2/10 amp fuse, or better, measure operating current and use about 2* that. > >PS >1) This is a motor used for a telescope clock drive. >2) The motor has a built in gearing so shaft rotates 2RPM > >respond via email to: > grossman@bbn.com > or > uunet!bbn!grossman >---------- Sorry, neither of those addresses worked for me .. I tried.