# US 2014/0265983 A1 · Method and Apparatus for Monitoring Motor Current for an Electric Valve Positioner

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- Number: US 2014/0265983 A1
- Document ID: US20140265983A1
- Status: Published application
- Kind: A1
- Application number: 14/202,414
- Filed: 2014-03-10
- Published: 2014-09-18
- Earliest claimed: 2013-03-14
- Assignees: Fisher Controls International LLC
- Applicants: Fisher Controls International LLC
- Inventors: Clyde T. Eisenbeis
- Web page: https://patentgrep.com/patent/US20140265983A1

## CPC

- H02P 29/02: Providing protection against overload without automatic interruption of supply (protection against faults of stepper motors H02P8/36)
- G05B 19/0428: {Safety, monitoring (G05B19/0423 takes precedence)}
- H02H 7/08: for dynamo-electric motors
- G05B 2219/14045: Parameter, over or under condition detection
- G05B 2219/14046: Current flow
- H02P: CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- G05B: CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS (systems for controlling or regulating non-electric variables G05D; systems for regulating electric or magnetic variables G05F; control devices or systems insofar as characterised by mechanical features only G05G)
- H02H: EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS (indicating or signalling undesired working conditions G01R, e.g. G01R31/00, G08B; locating faults along lines G01R31/08; emergency protective devices H01H)

## Abstract

A system and method for monitoring and controlling the amount of electrical current provided to a motor used to actuate a field device within a control system.

## Claims

### Claim 1

A control system including a valve, wherein the valve is positioned in response to an occurrence of an event trigger, the control system comprising:
a controller including a processor for controlling the valve, the controller further including a position input, a position output providing a position signal, and a control output providing a control signal;
a memory coupled to the processor;
a gate having a first state and a second state, the gate including a control input and a control output, wherein the control input of the gate is coupled to the control output of the controller;
a motor driver interface including a position input, a control input, and a control output, wherein the position input of the motor driver interface is coupled to the position output of the controller, and wherein the control input of the motor driver interface is coupled to the control output of the gate;
a motor driver including a control input and a control output, wherein the control input of the motor driver is coupled to the control output of the motor driver interface;
a motor coupled to the control output of the motor driver;
a current sensor operatively coupled between the motor and its power source, the current sensor for sensing current provided to the motor;
a position sensor coupled to the motor and the controller, wherein the position sensor provides a position of the motor to the controller; and
a comparator coupled to the current sensor and the gate, the comparator including a threshold current level and being capable of providing a state signal to the gate in response to a comparison of the current sensed by the current sensor and the threshold current level, wherein the state signal provided to the gate places the gate in the first state enabling a control signal from the controller to pass to the motor driver interface when the current sensed by the current sensor is less than the threshold current level, and wherein the state signal provided to the gate places the gate in the second state preventing the control signal from the controller to pass to the motor driver interface when the current sensed by the current sensor is equal to or greater than the threshold current level.

### Claim 2 (depends on 1)

The control system of claim 1, wherein the current sensor is a resistor.

### Claim 3 (depends on 1)

The control system of claim 1, wherein the current sensor is a Hall effect sensor.

### Claim 4 (depends on 1)

The control system of claim 1, wherein the position sensor is a Hall effect sensor.

### Claim 5 (depends on 1)

The control system of claim 1, further comprising a gear assembly coupled between the motor and the valve for facilitating positioning of the valve by the motor.

### Claim 6

A method of controlling a field device in a control system, the method comprising:
providing a memory device including a threshold current level;
detecting an occurrence of an event trigger;
sending a control signal to a motor to actuate a field device in response to detecting the occurrence of the event trigger;
monitoring an electrical current provided to the motor;
comparing the monitored electrical current provided to the motor to the threshold current level;
executing a first command if the monitored electrical current provided to the motor is less than the threshold current level; and
executing a second command if the monitored electrical current provided to the motor is equal to or greater than the threshold current level.

### Claim 7 (depends on 6)

The method of claim 6, wherein executing the first command includes enabling a gate to allow the control signal to pass through to the motor.

### Claim 8 (depends on 6)

The method of claim 6, wherein executing the second command includes disabling a gate to prevent the control signal from passing through to the motor.

### Claim 9 (depends on 6)

The method of claim 6 further comprising:
sensing a position of the motor; and
coordinating the sending of the control signal with the sensed position of the motor.

### Claim 10

A control system for controlling a process, the control system comprising:
a field device coupled to the process and arranged to control a process condition;
a motor coupled to the field device and configured to move a portion of the field device;
a controller including a processor and a memory, the processor being operatively coupled to the motor for controlling the motor to move the portion of the field device;
a current sensor coupled to the motor and arranged to monitor electrical current drawn by the motor; and
a control module coupled to the controller and capable of regulating passage of control signals transmitted to the motor for moving the portion of the field device.

### Claim 11 (depends on 10)

The control system of claim 10, wherein the control module includes:
a gate having a first state and a second state, the gate including a control input and a control output, wherein the control input of the gate is coupled to a control output of the controller; and
a comparator coupled to the current sensor and the gate, the comparator including a threshold current level and being capable of providing a state signal to the gate in response to a comparison of the current sensed by the current sensor and the threshold current level, wherein the state signal provided to the gate places the gate in the first state enabling a control signal sent by the controller to pass to the motor when the current sensed by the current sensor is less than the threshold current level, and wherein the state signal provided to the gate places the gate in the second state preventing the control signal sent by the controller to pass to the motor when the current sensed by the current sensor is equal to or greater than the threshold current level.

### Claim 12 (depends on 10)

The control system of claim 10, wherein the control module is capable of being stored on the memory and when executed on the processor, compares an amount of electrical current sensed by the current sensor to a threshold current level and allows a control signal sent by the controller to pass to the motor when the current sensed by the current sensor is less than the threshold current level, and prevents the control signal sent by the controller to pass to the motor when the current sensed by the current sensor is equal to or greater than the threshold current level.

### Claim 13 (depends on 10)

The control system of claim 10, wherein the current sensor is a resistor.

### Claim 14 (depends on 10)

The control system of claim 10, wherein the current sensor is a Hall effect sensor.

### Claim 15 (depends on 10)

The control system of claim 10, further comprising:
a position sensor coupled to the motor and the controller, wherein the position sensor provides a position of the motor to the controller.

### Claim 16 (depends on 15)

The control system of claim 15, wherein the position sensor is a Hall effect sensor.