D-C Bus current monitoring system
AssigneeBorg-Warner Corporation
InventorFrederick L. Hoadley
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Abstract
The d-c bus current, fed to an inverter through a low pass filter, having a shunt-connected capacitor, from the output of an a-c energized a-c to d-c converter (such as a phase-controlled SCR rectifier bridge), is monitored by using a-c current transformers to sense the filter capacitor current and the a-c current supplied to the converter. The transformer output signals are employed to produce a d-c signal which is a reduced amplitude replica of, and has the identical waveshape as, the d-c bus current. The monitoring system is electrically isolated from the power circuitry by means of the a-c current transformers.
Claims11
A monitoring system for monitoring the d-c bus current supplied over a d-c bus to an inverter and received through a low pass filter, having a series-connected filter choke and a shunt-connected filter capacitor, from the output of an a-c to d-c converter, to the input of which converter is applied a-c energy, said monitoring system comprising:
- input current sensing means, including at least one a-c current transformer and a rectifier, for sensing the a-c input current to the converter and deriving a d-c signal which is proportional to the d-c current produced at the output of the converter;
- capacitor current sensing means, including an a-c current transformer, for sensing the filter capacitor current to derive an a-c signal proportional thereto;
- and adding means for adding the two derived signals to produce a d-c signal which is directly proportional to, and very accurately represents, the d-c bus current.
In an inverter system where a-c power line voltage is rectified in a phase-controlled SCR rectifier bridge, after which the rectified line voltage is filtered and smoothed in a low pass filter to develop, across a shunt-connected filter capacitor, an adjustable d-c bus voltage, d-c bus current flowing from the filter to a voltage source inverter, a monitoring system for monitoring the d-c bus current comprising:
- input current sensing means, including a rectifier and a number of a-c current transformers equal to the number of phases of the a-c power line voltage, for sensing the a-c input line current to the controlled rectifier bridge to develop a d-c signal directly proportional to the d-c current produced at the output of the phase-controlled recitifier bridge;
- capacitor current sensing means, including an a-c current transformer, for sensing the filter capacitor current to produce a signal directly proportional thereto;
- and means for combining the signals produced by said input current sensing means and capacitor current sensing means to provide a d-c signal which is directly proportional to, and very accurately represents, the d-c bus current.
Dependencies are inferred from the claim text.