Current measuring arrangement of a frequency converter
AssigneeVacon Oyj
InventorsJaakko Ollila, Risto Komulainen, Lasse Kortelahti
Life of this patent
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Abstract
A method and a corresponding appliance for measuring the output current of a frequency converter, the frequency converter including a network bridge that can be connected to an AC network, a controllable three-phase load bridge that can be connected to an AC load, and a DC intermediate circuit between them, the DC intermediate circuit including a filter capacitor that includes controllable semiconductor switches in each phase and that are controlled by pulse-width modulation, and in which the currents of the output phases are determined based on measured samples of the current of the filter capacitor of the DC intermediate circuit.
Claims20
A method for measuring the output current of a frequency converter including a network bridge connectable to an AC network, a controllable three-phase load bridge connectable to an AC load, and a DC intermediate circuit between the network bridge and the controllable three-phase load bridge, the DC intermediate circuit including a filter capacitor, wherein the controllable three-phase load bridge contains a controllable semiconductor switch for each of the three phases, each controllable semiconductor switch controlled by pulse-width modulation, the method comprising:
- measuring samples of a current of the filter capacitor of the DC intermediate circuit in conjunction with switchings of the controllable semiconductor switches, including measuring a first sample when a gate control pulse of a first of the controllable semiconductor switches ceases and measuring a second sample after a delay subsequent to the starting of a gate control pulse of a second of the controllable semiconductor switches;
- and
- determining the output current of the frequency converter based on the measured samples,
- wherein the network bridge is one of an inactive network bridge and an active three-phase controllable network bridge having corresponding controllable semiconductor switches.
An appliance for measuring the output current of a frequency converter, comprising:
- a network bridge connectable to an AC network and including one of an inactive network bridge and an active three-phase controllable network bridge having corresponding controllable semiconductor switches;
- a controllable three-phase load bridge connectable to an AC load and including a controllable semiconductor switch for each of the three phases, each controllable semiconductor switch controlled by pulse-width modulation;
- a DC intermediate circuit between the network bridge and the controllable three-phase load bridge, the DC intermediate circuit including a filter capacitor,
- a control unit including a modulator configured to control the semiconductor switches of the controllable three-phase load bridge with pulse-width modulation;
- and
- a measuring sensor connected to the filter capacitor of the DC intermediate circuit, the measuring sensor controlled to
- measure samples of a current of the filter capacitor of the DC intermediate circuit in conjunction with switchings of the controllable semiconductor switches by measuring a first sample when a gate control pulse of a first of the controllable semiconductor switches ceases and measuring a second sample after a delay subsequent to the starting of a gate control pulse of a second of the controllable semiconductor switches, and
- determine the output current of the frequency converter based on the measured samples.
Dependencies are inferred from the claim text.