Electricity: motive power systems – Battery-fed motor systems
Patent
1974-05-31
1976-11-02
Dobeck, Benjamin
Electricity: motive power systems
Battery-fed motor systems
318331, 318493, 318532, H02P 506
Patent
active
039899900
ABSTRACT:
An electric vehicle having a separately excited field controlled direct current drive motor powered by a direct current power supply wherein field current is pulse-width modulated in response to operator control and the vehicle operating parameters. An armature current demand signal which is dependent on a throttle setting is compared with an actual armature current signal derived from an armature shunt and the difference is applied to a field current output amplifier which supplies current to the separately excited field to reduce the difference to zero. The armature current demand signal is responsive to the operator's control of the throttle in the electric vehicle. The drive motor of the electric vehicle can be operated in the driving mode for moving the electric vehicle or a regenerative mode for braking the electric vehicle and supplying energy to the power supply. The armature demand signal is also influenced by various operating conditions to improve operation of the electric vehicle. For example: in a high voltage connection, when regenerative braking voltages increase above a predetermined level the armature current demand signal is reduced; for a low voltage connection with a high current drain, if battery voltage falls below a predetermined level, such as 30 volts, the armature current demand signal is reduced; for high motor speeds above a given value such as 3,000 rpms, the armature current demand signal is reduced to limit commutation sparking; and, when field current excitation falls below a given minimum value the armature current demand signal is also reduced to limit commutator sparking and prevent possible motor damage. During vehicle operation a minimum pulse-width current signal is always applied to the separately excited field of the direct current drive motor to prevent overspeed and motor damage. To maintain smooth control of the electric vehicle, the armature current demand signal relative to a given throttle setting is shifted as a function of motor speed. Compensating means are provided to limit the variation of field excitation as a function of variation in battery voltages.
REFERENCES:
patent: 3546548 (1968-04-01), Wouk
patent: 3569809 (1971-03-01), Comer
patent: 3599064 (1971-08-01), Friedman
patent: 3735220 (1973-05-01), Renner et al.
patent: 3745434 (1973-07-01), Lambert
patent: 3845368 (1974-10-01), Elco
patent: 3855511 (1974-12-01), Smith
Dobeck Benjamin
Elchik W. A.
Westinghouse Electric Corporation
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