Electrical transmission or interconnection systems – Switching systems – Condition responsive
Patent
1983-05-12
1984-10-16
Pellinen, A. D.
Electrical transmission or interconnection systems
Switching systems
Condition responsive
307132EA, 361 43, 361166, 361170, 361195, 318779, 318799, 198855, H01H 3506
Patent
active
044777345
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND AND OBJECTS OF THE INVENTION
The present invention relates to a control system for an eddy current coupling drive for armoured face conveyors.
It is known to use eddy current coupling drives for conveyors and such couplings provide a controlled build up of torque and/or speed, and enable the load to be shared reasonably equally between drives when more than one drive is used on the conveyor. When applying the eddy current coupling drive to armoured face conveyors, account must be taken of the fact that the weight of excavated material on the conveyor can increase the frictional resistance and inertia such that considerable excess torque may be required to start the conveyor. It may not be possible to control, consistently, the required torque with the available eddy current coupling drive control system and in this situation the motors may stall. The supply voltages to the motors of several coupling drives may not be identical, resulting in varying maximum available torques, and thus making the application of maximum total torque more difficult. In addition, in longwall mining the drives may be at each end of the armoured conveyor, and these can be separated by several hundred metres. Normally, each eddy current coupling is supplied from a separate control unit which incorporates some form of control of a thyristor rectifier which supplies d.c. current to the excitation coils of the coupling. In a multi-motor drive as is used in armoured face conveyors, these control units are interlinked electrically, and may be mounted in a common enclosure with supply cables being connected to each coupling. If it is also desired to monitor speed signals from the coupling drive, this normally requires another cable between the control units and each coupling drive.
Similarly, measurement of the motor terminal voltage as a control parameter requires further cable between the coupling drives and the control unit. This accumulation of cables between the control units and the drives is impractical in the use of an armoured face conveyor.
It is an object of the present invention to obviate or mitigate the limitations of the existing conveyor control system.
SUMMARY OF THE INVENTION
According to the present invention, there is provided a control system for multiple eddy current coupling drives comprising:
an electrical power supply means including first switching means actuable to close, in response to a start signal, a contact in the circuit of a second switching means, and a timing means arranged to complete the circuit of the second switching means for a predetermined period thus enabling power to be supplied to the several coupling drives, and thereby energising a retaining relay in each coupling drive, said retaining relays having contacts being connected in series in a retaining circuit arranged to retain the said second switching means after said predetermined period has elapsed,
electronic control means integral with, or in close proximity to, each coupling drive and arranged to automatically initiate an increase of excitation applied to each coupling drive from an initial zero value to a preset maximum value over a preset time when power is applied to each coupling drive, said control means including means for inhibiting the increase in excitation in response to input speed signals, speed sensing means for monitoring the input and output speeds of the coupling drive, said input speed being compared with a predetermined level, said increase in excitation being inhibited when said input speed falls to the predetermined level, and
means for de-energising at least one retaining relay in response to timing means initiated by an inhibiting signal such that said at least one relay is de-energised after a preset time unless an output speed signal indicates that the conveyor is beginning to accelerate, thus interrupting said retaining circuit and interrupting power supply to all couplings.
Preferably said first and said second switching means include first and second relays respectively.
Alternatively, said fir
REFERENCES:
patent: 3017527 (1962-01-01), La Vallee
patent: 3076906 (1963-02-01), Simo
patent: 3586868 (1971-06-01), Martens et al.
patent: 4150303 (1979-04-01), Armstrong
patent: 4187525 (1980-02-01), Nagura et al.
patent: 4354747 (1982-10-01), Borowski et al.
patent: 4374353 (1983-02-01), Hasisohn
Method of Torque Reg. and Load Sharing In a Large Overload Conveyor by A. Ray, IEEE 12th Annal Meeting, Oct. 2-6, 1977.
Anderson Strathclyde PLC
Jennings Derek S.
Pellinen A. D.
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