Elevator Troubleshooting & Repair. David Herres

comfortable elevator operation and ride under changing usage conditions. The system incorporates intuitive control to provide smooth operation. When a hall call button is pressed, the optimum car responds based on waiting time, travel time, current car occupancy, and projected energy consumption.

      Otis is the world’s largest elevator manufacturer. We told the story in Chapter One of Elisha Otis’s invention in 1852 of safeties, which lock the car to guides fastened to the hoistway walls so that it can’t fall into the pit if the steel ropes fail.

      The Otis brand is well-known throughout the world. The firm maintains extensive research and testing facilities, and watches its competitors, who in turn watch Otis for industry-changing innovations, such as Kone’s machine room-less systems.

      Schindler Group, like many of its competitors, has enthusiastically embraced the MRL concept. The company currently employs over 58,000 people in the United States, Switzerland, India, Spain, Slovakia, Brazil, and China. Schindler was founded in 1874 in Switzerland and soon began manufacturing many types of machines including elevators. It rapidly expanded throughout Europe, the United States, South America, and China.

      Schindler has introduced Miconic 10, a proprietary control system. Passengers enter their destinations in a wall-mounted keypad while waiting for a car. The system groups riders with the same destination to a specific car, vastly increasing efficiency and reducing waiting time.

      ThyssenKrupp has continuously embraced new technologies such as double-decker cars, rope-less horizontally-moving cars, moving walks, heavy-machinery freight, and vehicle elevators. The company has 670 subsidiaries.

STUDY QUESTIONS

       1. The most common type of elevator is:

      A. machine room-less

      B. hydraulic

      C. traction

      D. aeronautic

       2. Traction elevators are characterized by:

      A. water power

      B. freight only

      C. an operator

      D. steel ropes

       3. The gearless design permits car speeds in excess of:

      A. 100 fpm

      B. 500 fpm

      C. 1000 fpm

      D. 2000 fpm

       4. Compensation is needed when vertical travel is greater than:

      A. 100 feet

      B. 250 feet

      C. 500 feet

      D. 1000 feet

       5. Compensation consists of:

      A. a greater amount of insurance

      B. hanging chain to add weight

      C. good judgment on the part of technicians

      D. higher speed for a smoother ride

       6. Steel belts can be used rather than steel rope. They require:

      A. frequent lubrication

      B. more power to run

      C. less material weight

      D. a skilled operator

       7. Traction elevator motors with gearless drives:

      A. are smaller

      B. operate at lower RPM

      C. require more maintenance

      D. can be noisy

       8. Roping configurations in a traction elevator:

      A. consist of suspension ropes attached to the top of the car

      B. may be underslung

      C. pass down to the counterweight

      D. any of these

       9. The gearless design requires:

      A. higher car speed

      B. a smaller sheave

      C. frequent lubrication

      D. frequent rebuilding

      10. In a regenerative drive system, energy is returned to the grid:

      A. when a full car is ascending

      B. when an empty car is descending

      C. when a full car is descending

      D. when the car is stopped

      For answers, go to Appendix A.

CHAPTER 3

       AC AND DC ELECTRIC MOTOR MAINTENANCE, VFD TROUBLESHOOTING, AND DIAGNOSTIC PROCEDURES

      Almost all modern elevators, traction and hydraulic, are driven by electric motors. Until the development of the VFD in the 1960s, electric elevators invariably made use of the DC as opposed to the AC motor because the former permitted simple, smooth speed control. That was essential for stopping the car at individual floors and also for running in inspection mode.

      Since the introduction and widespread use of AC motors in conjunction with VFDs, three-phase induction motors have been used in most new construction and major rebuilds, although in the latter, a case can be made for retaining a good working DC motor. Parts and entire replacement motors are readily available and the most common repair, brush replacement, is not difficult.

      In this chapter, we will discuss DC and AC motor maintenance, as shown in Figure 3-1, beginning with some comments that apply to both.

Good Motor Maintenance

      Some first signs of motor trouble are failure to start, excessive or unusual noise, reduced power, odor from insulation breakdown, overheating, and tripping out. These symptoms often occur in combination, although at first only one of them may be apparent.