Donald J. Simon, Sargent Industries Inc., Oil Well Equipment Division
Ultra-high-slip motors with speed variation capabilities in the range of 45% have been used on beam pumping installations for more than six years. As various producing companies started trying these motors, many improvements in system operation were noted, including: 1. Reduction in peak polished rod load 2. Increase in minimum polished rod load 3. Improved rod life 4. Reduction in peak torque by the API Torque Factor Method 5. A greatly altered dynamometer card shape which showed a tendency to approach the rectangular or parallelogram configuration 6. More production at the same strokes per minute 7. Greatly reduced current (ampere) peaks 8. Greatly reduced RMS (thermal) ampere requirement with a resulting improvement in power factor 9. A much steadier energy (kilowatt) requirement with frequent reductions in total kwh required. 10. Reduced distribution system voltage drop 11. Slower and smoother start-up of the pumping system with a visual recognition that its start-up was less strain on all components of the system 12. A greatly reduced start-up current demand which reduced the possibility of voltage collapse from heavy system loading. These dramatic results created much enthusiasm among those who were involved with the operation and use of the motor. It was assumed by some that all these dramatic results would be obtained on every well in every condition, but that was not the case. On some wells no improvement in dynamometer card shape or rod loading was noted with no apparent improvement in torque loading on the gear box. These tests, which were seemingly failures, caused many interested industry people to doubt the value of an ultra-highslip motor. Some even stated that it had no value or was detrimental to the system. Many heated and enlightening discussions ensued which contributed greatly to the present understanding of the total system operation.