Otis Elevator Case Study

The problem with the elevator was the inability of maintaining speed control. The controller was checked and many of the boards were replaced with no success. The customer wanted to have the motors tested before modernization took place to determine the electrical integrity of the windings. It was found in Car # 9 that a field coil was so bad that the coil had almost no magnetic properties.(See test data below). Coil was rewound and the speed control was reestablished.


CAR # 9

	12 o’clock	2 o’clock	4 o’clock	6 o’clock	8 o’clock	10 o’clock
Resistance	6.8493	0.0116	7.4354	7.0797	6.5586	7.0305
Impedance	538	58	522	527	529	530
Inductance	857	9687	831	840	842	844
Phase Angle	64	16	62	62	62	64
I/F Ratio	-30	-3	-33	-30	-30	-30

Care # 8

	12 o’clock	2 o’clock	4 o’clock	6 o’clock	8 o’clock	10 o’clock
Resistance	7.5077	7.621	7.6514	7.0277	7.6963	7.6812
Impedance	513	572	512	598	568	573
Inductance	817	911	815	949	903	912
Phase Angle	63	63	63	62	61	62
I/F Ratio	-35	-34	-36	-35	-35	-36