Electricity: motive power systems – Braking – Automatic and/or with time-delay means
Patent
1991-04-23
1992-02-25
Shoop, Jr., William M.
Electricity: motive power systems
Braking
Automatic and/or with time-delay means
318275, H02P 300
Patent
active
050916807
ABSTRACT:
A device for braking a rotating magnetic disk in a magnetic storage system senses a back EMF generated by a drive spindle motor. By electrically shorting the coils in the drive spindle motor the rotation of the magnetic disk is stopped. The back EMF is compared with a reference voltage. The reference voltage is selected so that the rate of rotation of the magnetic disk is large enough that a magnetic head "flies" over the surface of the disk, but small enough so that surge currents in the drive spindle motor will not damage the motor coils. Field effect transistors are used to electrically short the coils. A holding capacitor holds a voltage on the gates of the FETs upon loss of power to the magnetic storage system. A reset circuit draws charge from the holding capacitor upon power-up of the storage system.
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IBM Technical Disclosure Bulletin, "Motor Control Having BEMF Dynamic Braking", vol. 14, No. 2 (Jul. 1971).
Seagate Technology Inc.
Shoop Jr. William M.
Wysocki A. Jonathan
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