| 摘要 |
1467316 Control of D.C. motors HITACHI Ltd 28 June 1974 [2 July 1973] 28835/74 Heading H2J The series D.C. motor M, F of a railway tramcar is connected to an overhead feeder line L through a pantograph collector P and a regenerative braking circuit consisting of a thyristor chopper CH and members LF, LM, CF, DS, DB, reliable operation of this circuit when the motor is initially changed from a driving to a regenerative mode being ensured by an excitation circuit SA, RA, which supplies the field winding F from the line L during the start of regeneration, a typical cycle of braking being as follows: (1) When motor M is switched from its driving to its regenerative mode, switch SA is closed to supply the field F through resistor RA, reactor LM and the chopper CH (after its closure), the chopper mark/space ratio then being controlled by a closed loop system, Fig. 3 (not shown), to produce a desired large field current and a rapid increase of the voltage generated by the motor, the resistor RA acting as a current limiter during the period. (2) When the voltage generated by the motor has reached a predetermined level, e.g. after about 1 to 2 seconds, switch SA is opened and regenerative braking is produced at a desired rate by controlling the mark-space ratio of the chopper CH with the closed loop control system. When the chopper is conductive, series generator operation occurs through members M, F, LM, CH, DB and when CH is non-conductive, stored energy (mainly in reactor LM) is returned to the supply through the circuit M, F, LM, DS, LF, P, L, E and DB. The following modifications are also described: (1) Members F, LM are interchanged and resistor RA is connected to their junction point, Fig. 5 (not shown). In this case diode DB may be omitted. (2) Resistor RA is connected to the junction between members M, DB, Fig. 6 (not shown). (3) Diode DB is replaced by a switch (SB), which is open at the start of regeneration and closes when the generated motor voltage reaches a predetermined level, Fig. 7 (not shown). (4) Resistor RA is replaced by a reactor (LA) of inductance and resistance considerably greater than those of reactor LM, Fig. 8 (not shown). (5) Members M, F are connected in parallel with the series combination of a switch (SC) and resistor (RB), the switch being interlocked with switch SA for simultaneous closure and the value of resistor (RB) being such that the field F is also energized when the chopper CH is open, whereby the generated motor voltage is more rapidly increased, Fig. 9 (not shown). The modification shown in Fig. 10 use as second thyristor chopper CHA to supply and control the field current, a transistor oscillator, Fig. 12 (not shown), of variable frequency controlling the chopper CHA and having a switch (SI) which is closed at the start of regeneration (to start the oscillator) and opened when the generated motor voltage has reached a predetermined level (to stop the oscillator). When the motor is stationary, switch SA may be closed to obtain a D.C. supply for testing the chopper CH. |
