1. Understanding and Improving the Regenerative Brake Operation of Commercial Motor Car Trains

      A system was developed for remote measurement of the regenerative brake operation condition and reliability of commercial motor car trains using LAN and cellular phones within the train (Fig. 1). This system can evaluate regenerative brake performance in terms of reliability and availability.
(1) Reliability indicates the average mean time interval between occurrences of regenerative brake cancellation events (states in which the electric braking force is zero due to protection) measured by cause (equipment failure, large-scale skids, and contact losses).
(2) Availability indicates the ratio of the total braking force (while the brake is actually in use) to the total regenerative braking force while the regenerative brake is directed.
Regenerative brake operation data collected on JR commuter trains equipped with this system (Fig. 2) over a period of approximately one year showed the following:
(i) No regeneration was cancelled due to equipment failure or large-scale skids. The reliability of the regenerative brake at the equipment level seems to be relatively high.
(ii) The average availability of the regenerative brake is around 80 to 90%, with no difference in availability among vehicles/axle sets in the train set.
(iii) The availability of the regenerative brake normally decreases by about 10% due to a skid. If a light load was added (as in Fig. 3), the availability decreased by up to 40%. It was shown that light load events affected the effective use of the regenerative brake more than skid occurrence.
(iv) Average power consumption per half hour classified by operation (new rapid /rapid, day of week weekdays/Saturdays and holidays) and time zone (commuter time 8:00-8:30/daytime 12:00-12:30), showed that differences by operation are the greatest, with a variation of up to 30%. Power consumption by the auxiliary machine is about 10% on average compared to that of the main power circuit (i.e. power consumed by power running - regenerated power) and up to 25% in extreme cases (Fig. 4).

      The above results showed the reliability of the regenerative brake at equipment level to be relatively high, and that availability is strongly affected by light loads. Improvements in availability will also lead to energy saving.
      Reliability and availability can also be used as criteria for determining regenerative/non-regenerative brake sections. Effects can be measured quantitatively by focusing countermeasures on sections where reliability is low with frequent occurrences of failure or low availability, and making numeric comparisons before and after taking such measures. This system has in fact been used to check changes in the number of failures before and after taking measures against contact losses.
      The system has already been used on JR commuter trains.

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