System and method for limiting energy in an industrial control system
AssigneeInvensys Systems, Inc.
InventorKurt J. Otto
Life of this patent
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Abstract
A system and method for limiting energy to an industrial control system is described. The method includes receiving a supply voltage, limiting the supply voltage so as to generate a limited voltage, and providing the limited voltage to a field transducer, the field transducer being disposed to monitor a parameter of the industrial process. A field current, that is generated in response to the limited voltage, is received from the field transducer and the field current is indicative of a magnitude of the parameter under normal operating conditions. During a fault condition, the field current is restricted with a variable resistance that is responsive to an amount of thermal energy generated during the fault condition so as to limit an amount of energy drawn by the control system.
Claims13
An apparatus for controlling temperature, voltage and energy in an industrial process controller, comprising:
- a PTC device having an input disposed to be coupled to a voltage source;
- a first zener diode having a negative terminal coupled to an output of the PTC device and a field device output terminal, and a positive terminal coupled to a V- reference terminal;
- a second zener diode having a positive terminal coupled to the V- reference terminal and a negative terminal coupled to a field device input terminal;
- and
- a resistor coupled between the field device input terminal and the V- reference terminal so as to generate an output voltage signal proportional to a field current provided from the field device.
A system for controlling a process in an explosive environment, comprising:
- a field device disposed to sense a parameter of the process;
- a sensor sub-system disposed to control the operation of the field device, the sensor sub-system comprising:
- a PTC device having an input disposed to be coupled to a voltage source;
- a first zener diode having a negative terminal coupled to an output of the PTC device and an output terminal of the field device, and a positive terminal coupled to a V- reference terminal;
- a second zener diode having a positive terminal coupled to the V- reference terminal and a negative terminal coupled to an input terminal of the field device;
- and
- a resistor coupled between the input terminal of the field device and the V- reference terminal so as to generate an output voltage signal proportional to a field current provided from the field device;
- and
- a processor sub-system coupled to the field device.
Dependencies are inferred from the claim text.