Detection of unsafe voltages on mobile equipment
First Claim
1. Protective means for detecting the existence of an unsafe potential between earth and mobile equipment to which an AC voltage source is applied, comprising an electrically conductive member disposed between the equipment and earth, detecting means for detecting the electric field strength between the mobile equipment and earth at the location of the conductive member, the detecting means detecting the electric field strength irrespective of any earth connection or earth leakage current between the mobile equipment and earth, the detecting means deriving from said electric field strength a signal representative of the potential difference between the mobile equipment and earth, and disconnection means fed by said signal from the detecting means and operative to disconnect the voltage source from the mobile equipment when said signal corresponds to a dangerous potential of the mobile equipment with respect to earth.
2 Assignments
0 Petitions
Accused Products
Abstract
Protective equipment detects the existence of an unsafe potential (V2) between earth and mobile equipment such as a mobile cabin. A metal plate (14) is mounted below the chassis (10) of the cabin, and the voltage (V3) between the metal plate (14) and the chassis (10) is detected by an amplifier (16). The amplifier output feeds a threshold detector (18) which senses when the voltage (V3) reaches a level corresponding to a predetermined dangerous potential (V2) of the chassis (10) with respect to ground (12).
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Citations
7 Claims
- 1. Protective means for detecting the existence of an unsafe potential between earth and mobile equipment to which an AC voltage source is applied, comprising an electrically conductive member disposed between the equipment and earth, detecting means for detecting the electric field strength between the mobile equipment and earth at the location of the conductive member, the detecting means detecting the electric field strength irrespective of any earth connection or earth leakage current between the mobile equipment and earth, the detecting means deriving from said electric field strength a signal representative of the potential difference between the mobile equipment and earth, and disconnection means fed by said signal from the detecting means and operative to disconnect the voltage source from the mobile equipment when said signal corresponds to a dangerous potential of the mobile equipment with respect to earth.
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2. Protective means according to claim 2, wherein said means for detecting the electric field strength comprise a high impedance amplifier.
Specification