Electric power conversion systems – Current conversion – With conductive support mounting
Reexamination Certificate
2000-11-22
2001-10-23
Riley, Shawn (Department: 2838)
Electric power conversion systems
Current conversion
With conductive support mounting
C336S118000
Reexamination Certificate
active
06307766
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a system for transferring power without direct contact through the use of high frequency electromagnetic induction. In particular, this invention relates to a contactless power supply that also transfers control information at the same time through the same mechanism that transfers the power.
2. The Prior Art
Machine slides are generally powered directly by a motor through wires that connect the stationary power supply to the motor on the moving part of the slide. Since in many applications, the slide moves back and forth hundreds of times during an operation, the wires tend to wear very easily, and require frequent replacement. In addition, the weight of the wires, especially with large slides, can add significantly to the power requirements, and increase the inertia of the moving part of the slide.
It is therefore desirable to power a slide or other mechanism without using wires between the moving and stationary parts. One way to do this is through electromagnetic induction. This method is shown in U.S. Pat. No. 5,737,211 to Hirai et al. This patent shows the operation of a moving slide having a toroid through which wires from the stationary platform are run. The current from the wires induces a current in the toroid, which powers the slide without direct contact between the wires and the slide itself. While this device is useful for some purposes, it does not provide a way for controlling the power over the same lines.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide a contactless power supply that also supplies control signals over the same lines as the power.
This and other objects of the invention are accomplished by a power supply comprising a stationary unit and a movable unit that moves linearly in relation to the stationary unit, a primary conductor disposed on the stationary unit and a secondary conductor disposed on the movable unit. The primary conductor comprises a power supply having an amplifier for supplying high frequency alternating current. There are a plurality of wires extending from the power supply along the stationary unit for carrying the current, and three switches arranged on the wires in parallel with each other. Each switch alternates closing with the other switches to create a three phase alternating current for powering the secondary conductor. There is also a controller connected to the power supply for controlling the operation of the power supply.
The secondary conductor is arranged coaxially with the wires and comprises a toroidal core surrounding the wires, and a three phase motor connected to the core and powered via induction from the power supply, to slide the movable unit relative to the stationary unit. Thus, no wires are needed to connect the primary to the secondary conductor. There is a second controller connected to the motor for controlling the operation of the motor, and three switches connected in parallel between the motor and second controller for conducting the current in a three-phase circuit.
A current is generated in the wires of the primary conductor, which induces a current in the secondary conductor to power the motor and move the movable unit in relation to the stationary unit. To control the operation of the power supply device, there is a Hall sensor arranged in the secondary conductor for sending signals to communicate the status of the power to the first and second controllers. There is also a device to synchronize the primary conductor and secondary conductors. The switches on the primary and secondary conductors serially open and close to transfer three-phase alternating current from the amplifier to the motor. This insures a smooth power transfer. The device according to the invention also allows control signals to travel over the same wires as the current supplying the power.
The device for synchronizing the primary and secondary conductors comprises a sync pulse generator connected in parallel with the switches on the primary conductor. The sync pulse generator sends a sync pulse to the secondary conductor at predetermined intervals.
There is a Hall sensor signal coder connected to the secondary conductor, and a Hall sensor signal decoder connected to the primary conductor. The decoder decodes signals encoded by the coder to transfer information between the first and second controllers. The coder and decoder are needed because the Hall sensor sends out signals in DC of from 0-5V, which cannot be transferred between the primary and secondary. Thus, the signals must be coded into an AC signal by the coder. The Hall device sends three different signals, each signal corresponding to a phase of the motor.
The amplifier preferably emits a 16 mHz signal. The signal from the amplifier is divided using time division modulation, with one system period being 52 &mgr;s. There are preferably 11 periods comprising S
0
to S
7
, and SA-SC within each system period. S
0
to S
7
are 2 &mgr;s each with a 2 &mgr;s interval between S
1
and S
2
, and a 1 &mgr;s interval between S
4
and S
5
and S
5
and S
6
. S
1
and S
2
are used for transmission of signals from the sync pulse generator, S
3
to S
7
are used for transmitting signals from the Hall devices, and SA-SC are used for controlling time division modulation of the 3 phase motor.
SA, SB and SC are each 10 &mgr;s and correspond to a phase of the motor. There is a 1 &mgr;s interval between SA and SB, and SB and SC. The interval between the different periods prevents signal overlap due to propagation delay of optocouplers in the primary and secondary conductors.
The sync pulse generator outputs sync signals S
1
and S
2
to provide a positive pulse and a negative pulse, An optocoupler in the secondary conductor applies the pulses to the second controller as a synchronization signal.
Each switch is preferably a solid bidirectional switch or a semiconductor switch. The motor is preferably a linear motor.
REFERENCES:
patent: 5737211 (1998-04-01), Hirai et al.
patent: 6233834 (2001-05-01), Walsh
Feinstein Alan
Ross Joseph
Zhu Jack
Bayside Controls, Inc.
Collard & Roe P.C.
Riley Shawn
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