24-12-2020 дата публикации
Номер: US20200403537A1
Techniques for monitoring the health of a three-phase induction motor are provided. An expected threshold value is calculated as a function of an expected ratio of current unbalance to voltage unbalance for the three-phase motor. Embodiments determine whether a measured current unbalance exceeds the expected threshold value. Responsive to the measured current unbalance exceeding the expected threshold value, a remedial action may be taken, such as generating diagnostic information or activating one or more protection operations for the three-phase induction motor. 1. A method , comprising:calculating, by a three-phase protective device, an expected current unbalance, as a product of a measured voltage unbalance times an expected ratio of current unbalance to voltage unbalance for a three-phase load;calculating, by the three-phase protective device, an expected threshold current unbalance indicating a potential fault caused by unbalanced currents, as the expected current unbalance plus a value of unbalance tolerance/sensitivity;determining, by the three-phase protective device, whether a measured current unbalance exceeds at least one of the expected current unbalance or the expected threshold current unbalance; andproviding, by the three-phase protective device, an action for the three-phase load, based on the determination.2. The method of claim 1 , further comprising:determining, by the three-phase protective device, that the measured current unbalance exceeds the expected current unbalance; andproviding, by the three-phase protective device, diagnostic information for the three-phase load, based on the determination.3. The method of claim 1 , further comprising:determining, by the three-phase protective device, that the measured current unbalance exceeds the expected threshold current unbalance; andproviding, by the three-phase protective device, protection for the three-phase load, based on the determination.4. The method of claim 1 , further comprising: ...
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