Technical Reports

Inverter-Controlled ac Induction Motor Propulsion System Volume I: Executive Summary

  • 01
  • Mar
  • 1989
AUTHOR: Jim Clemence
OFFICE: RPD
REPORT NUMBER: UMTA-CA-06-0175-89-1
SUBJECT: Motive Power and Equipment
KEYWORDS: ac Traction Motor, dc Chopper, Inverter Drive Unit, Power Conversion Unit, Pulse-Width Modulation
ABSTRACT: An inverter-controlled ac induction motor propulsion system for rail transit cars was designed, developed, and tested to verify projected benefits and applicability of ac over conventional dc cars. Two New York City Transit Authority (NYCTA) R-44 dc subway cars were retrofitted with prototype ac propulsion equipment based on mature, low-risk ac propulsion technology. The program showed that propulsion systems using ac motors can provide greatly improved reliability and reduced maintenance, with significant reductions in life-cycle cost. The prototype ac propulsion system conserves energy through regenerative braking, returning energy to the line when the network is receptive. The equipment consists of a control unit incorporating solid-state integrated circuits and two essentially independent truck drives. For each truck, a single inverter unit powers two totally enclosed, self-cooled, squirrel-cage ac induction motors, each motor driving one of the two axles per truck. Each pulse-width-modulated, voltage-fed, thyristor-controlled inverter is forced-air cooled by a blower, which also cools the resistors used to dissipate dynamic braking energy when the line is not receptive. Demonstrated on the NYCTA, the ac propulsion system improved acceleration and braking performance with good electromagnetic interference and acoustic noise control and was fully compatible with the existing trainlines, NYCTA signalling and supervisory equipment, and dc cars. The report explains how the latest technology would be applied in future production equipment to result in even more benefits to the rail transit industry. Volume I contains the executive summary; Volume II contains final report Sections 1 through 5.

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