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In Reply to: Need help with Ashland motor and capacitor posted by banpuku on August 13, 2012 at 09:43:38:
Whilst I have no experience with the Ashland motor it sounds like you need a Steinmetz connection*.
For this connection the AC supply goes across two of the three motor windings. The capacitor connects between one of these terminals and the third (free) winding, so the three mconnections are:
Phase 1, AC supply and one end of capacitor.
Phase 2 and AC supply only (other phase, natch)
Phase 3 and other end of capacitor only.
The order of the windings will determine the rotational direction of the motor. If you wire it up and the motor runs the opposite way to that required, simply swap terminals 2. and 3. above.
AC rated capacitors do not have polarity, so it doesn't matter which cap terminal is used for which connection.
Before you start wiring, check the resistance between each of the three possible pairings of motor wires (green to blue/red, black to blue/red and green to black.) They should all be within a few percent of each other. If this is not the case get back to me.
It should be noted that the Steinmetz connection has several drawbacks. The third phase created by the capacitor is only approximately correct, and even then only at one value of load. It is usual to have this occur at the highest continuous load and for that to be no more than 80% of the design rating for the motor. At all other loads the phase is further off, one effect of which is that the start torque for the motor is greatly reduced, often less than 20% of design rating.
The practical upshot of this is that you may find that the 3 uF value doesn't give you the best phase balance for your load. You may need to try different values to get closer to balance.
*One caveat, generally the capacitor size for a Steinmetz connection on an induction motor is 70uF per kW motor power. Your recommended cap is about twice that but the extremely poor efficiency of the hysteresis motor would probably be enough to create that difference.
Mark Kelly
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Follow Ups
- Steinmetz connection - Mark Kelly 03:38:05 08/14/12 (9)
- Balanced power supply? - CometCKO 19:08:25 08/14/12 (2)
- Not for this motor - Mark Kelly 23:07:44 08/14/12 (1)
- What a coincidence! - CometCKO 14:28:10 08/15/12 (0)
- RE: Steinmetz connection - banpuku 05:11:32 08/14/12 (3)
- RE: Steinmetz connection - banpuku 10:53:24 08/14/12 (0)
- Post a phot - Mark Kelly 05:52:56 08/14/12 (1)
- RE: Post a phot - banpuku 06:02:03 08/14/12 (0)
- RE: Steinmetz connection - banpuku 04:33:58 08/14/12 (1)
- Beyond me. - Mark Kelly 05:46:39 08/14/12 (0)