Variable frequency drive self-check
First Claim
1. A method, comprising:
- providing a variable frequency drive including a DC bus configured to provide a positive DC voltage and a negative DC voltage to an inverter, wherein the inverter includes one or more pairs of transistors, wherein an upper transistor of the one or more pairs of transistors is configured to receive the positive DC voltage and a lower transistor of the one or more pairs of transistors is configured to receive the negative DC voltage; and
before operating the variable frequency drive to drive a motor, operating a controller operatively coupled with the variable frequency drive to complete a set of pre-operation tests, the set of pre-operation tests performed by the controller comprising;
testing for a short circuit condition of one or more of the transistors including switching the transistors off, measuring a voltage at a node in electrical communication with an output of one or more of the transistors, and evaluating the voltage relative to a first expected value,testing for an open circuit condition of one or more of the transistors including switching the transistors off, switching on one of the transistors, measuring a voltage at a node in electrical communication with an output of the transistor switched on, and evaluating the voltage relative to a second expected value, andtesting for a sensor error condition of one or more current sensors including switching on an upper transistor coupled to a first node and switching on a lower transistor coupled to a second node, measuring a first current at the first node and a second current at the second node, and evaluating the first current and the second current relative to one another.
1 Assignment
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Accused Products
Abstract
Diagnostic and/or control methods, systems and apparatuses for variable frequency drives are disclosed. The variable frequency drive may be controlled by a controller that may conduct one or more tests or evaluations. The tests or evaluations may include determining whether a switching device in the variable frequency drive is open-circuited, short-circuited, or operating normally. The tests may include determining whether current provided at an inverter output of the variable frequency drive is within a predetermined range. An exemplary embodiment evaluates the drive for a short circuit condition, an open circuit condition, and a sensor error or failure condition, controls operation of the drive based upon these one or more evaluations, may abort operation of the drive based upon one or more evaluations, and may set a fault code indicative of the type of error encountered.
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Citations
29 Claims
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1. A method, comprising:
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providing a variable frequency drive including a DC bus configured to provide a positive DC voltage and a negative DC voltage to an inverter, wherein the inverter includes one or more pairs of transistors, wherein an upper transistor of the one or more pairs of transistors is configured to receive the positive DC voltage and a lower transistor of the one or more pairs of transistors is configured to receive the negative DC voltage; and before operating the variable frequency drive to drive a motor, operating a controller operatively coupled with the variable frequency drive to complete a set of pre-operation tests, the set of pre-operation tests performed by the controller comprising; testing for a short circuit condition of one or more of the transistors including switching the transistors off, measuring a voltage at a node in electrical communication with an output of one or more of the transistors, and evaluating the voltage relative to a first expected value, testing for an open circuit condition of one or more of the transistors including switching the transistors off, switching on one of the transistors, measuring a voltage at a node in electrical communication with an output of the transistor switched on, and evaluating the voltage relative to a second expected value, and testing for a sensor error condition of one or more current sensors including switching on an upper transistor coupled to a first node and switching on a lower transistor coupled to a second node, measuring a first current at the first node and a second current at the second node, and evaluating the first current and the second current relative to one another. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A system, comprising:
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a motor; a variable frequency drive structured to provide AC power to the motor, wherein the variable frequency drive includes a DC bus and an inverter, the DC bus includes a positive DC rail and a negative DC rail, the inverter includes a switching device, and the switching device is coupled to the positive DC rail and the negative DC rail; and a controller configured to execute a set of tests prior to operating the variable frequency drive to drive a motor, the set of tests performed by the controller comprising; test for a short circuit of the switching device including turning the switching device off, determining an output voltage at a terminal in electrical communication with an output of the switching device, and evaluating the output voltage relative to a first reference value, test for an open circuit of the switching device including turning the switching device off, turning on one at least a portion of the switching device, determining an output voltage at a terminal in electrical communication with an output of the portion of the switching device turned on, and evaluating the output voltage relative to a second reference value, and test for a sensor failure of one or more current sensors including measuring a first current at a first terminal of the switching device and measuring a second current at a second terminal of the switching device, and evaluating the first current and the second current relative to one another. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20, 21)
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22. An apparatus, comprising:
a non-transitory computer readable medium configured with instructions executable by a controller to perform a set of tests as pre-conditions on operation of the variable frequency drive to drive a motor, the set of tests comprising; a first test for a short circuit of a switching device in an inverter including turning the switching device off, measuring an output voltage of the switching device, measuring a voltage of a DC bus coupled to the inverter, and evaluating the switching device output voltage and the DC bus voltage relative to a reference value, a second test for an open circuit of the switching device including turning on a portion of the switching device, measuring an output voltage of the portion of the switching device turned on, measuring the voltage of the DC bus, and evaluating the output voltage of the portion of the switching device turned on and the DC bus voltage relative to the reference value, and a third test for a sensor failure of one or more current sensors including measuring a first current at a first node of the switching device and measuring a second current at a second node of the switching device, and evaluating the first current and the second current relative to one another. - View Dependent Claims (23, 24, 25, 26, 27, 28, 29)
Specification