Method for detecting earth-fault conditions in a motor controller
First Claim
1. A method for determining the existence of an earth-fault on-the-fly and thereby protecting a motor controller having a high- and a low-side DC-link, and having high- and low-side switching elements, the high- and low-side switching elements being operatively connected to the high- and low-side DC-link buses, respectively, the method comprising the steps ofgenerating a fault signal, said fault signal indicating abnormal working conditions for the motor controller,switching off all of the switching elements,generating at least one test vector in response to the fault signal by switching at least one of the switching elements on after all of the switching elements have been switched off, andmeasuring, while the at least one switching element is on, the magnitude of a current flowing in that DC-link operatively connected to the conducting switching element(s) in order to detect an earth-fault.
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Abstract
The present invention relates to a method for determining the existence of an earth-fault on-the-fly and thereby protecting a motor controller having a high- and a low-side DC-link, and having high- and low-side switching elements, the high- and low-side switching elements being operatively connected to the high- and low-side DC-link buses, respectively, the method comprising the steps of generating a fault signal, generating at least one test vector in response to the fault signal by switching at least one of the switching elements on, and measuring, while the at least one switching element is on, the magnitude of a current flowing in that DC-link operatively connected to the conducting switching element in order to detect an earth-fault. The present invention further relates to additional methods for on-the-fly determination of earth-faults.
31 Citations
26 Claims
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1. A method for determining the existence of an earth-fault on-the-fly and thereby protecting a motor controller having a high- and a low-side DC-link, and having high- and low-side switching elements, the high- and low-side switching elements being operatively connected to the high- and low-side DC-link buses, respectively, the method comprising the steps of
generating a fault signal, said fault signal indicating abnormal working conditions for the motor controller, switching off all of the switching elements, generating at least one test vector in response to the fault signal by switching at least one of the switching elements on after all of the switching elements have been switched off, and measuring, while the at least one switching element is on, the magnitude of a current flowing in that DC-link operatively connected to the conducting switching element(s) in order to detect an earth-fault.
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21. A method for determining the existence of an earth-fault on-the-fly and thereby protecting a motor controller having a high- and a low-side DC-link, and having high- and low-side switching elements, the high- and low-side switching elements being operatively connected to the high- and low-side DC-link buses, respectively, the motor controller further comprising a motor controller unit for controlling when the switching elements are to be switched on and off by generating a PWM signal to each of the switching elements, the method comprising the steps of
modifying the generated PWM signal by increasing the duty cycle of at least one of the PWM signal applied to the low-side switching elements, the increase of the duty cycle having a time period being a fraction of the switching period of the low-side switching elements, generating and hereby applying a 000 test vector, and measuring, while the low-side switching elements are on, the magnitude of a current flowing in the low-side DC-link in order to detect an earth-fault, wherein the 000 test vector is generated and applied at a rate lower than the switching frequency of the low-side switching elements.
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25. A method for determining the existence of an earth-fault on-the-fly and thereby protecting a motor controller having a high- and a low-side DC-link, and having high- and low-side switching elements, the high- and low-side switching elements being operatively connected to the high- and low-side DC-link buses, respectively, the motor controller further comprising a motor controller unit for controlling when the switching elements are to be switched on and off by generating a PWM signal to each of the switching elements, the method comprising the steps of
modifying the generated PWM signal by increasing the duty cycle of at least one of the PWM signals applied to the high-side switching elements, the increase of the duty cycle having a time period being a fraction of the switching period of the high-side switching elements, generating and hereby applying a 111 test vector, and measuring, while the high-side switching elements are on, the magnitude of a current flowing in the high-side DC-link in order to detect an earth-fault, wherein the 111 test vector is generated and applied at a rate lower than the switching frequency of the high-side switching elements.
Specification