Control apparatus for inverter
First Claim
1. In a control apparatus for an inverter wherein an A.C. power source is subjected to variable-frequency and variable-voltage conversion to drive an induction motor at a variable-speed;
- an inverter control apparatus comprising;
a first current level setting unit (5) for establishing a predetermined current level within a permissible limit of switching elements disposed in the inverter, a second current level setting unit (7) for establishing a current level at a slip value corresponding to a stall torque, in association with a characteristic of the loaded induction motor and an output voltage/output frequency ratio, a current level selector (8) for selecting the smallest one of the output signals of said first and second current level setting units, a current detector (4) for detecting the inverter output current, and control means (6) for controlling the switching elements in response to a velocity command, the output of the selected current level setting unit, and the detected inverter output current to render the inverter output current smaller than the selected current level signal.
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Accused Products
Abstract
An inverter control apparatus comprises a first current level setting unit 5 which sets a protection level for switching elements included in an inverter 1, and a second current level setting unit 7 which sets a current level that prevents a stall torque/slip point from being exceeded and which is determined in association with the load characteristic of an induction motor and the voltage/frequency ratio being delivered by the inverter. The smaller of the two current levels is selected to control the frequency to lower or stop its rise to prevent the slip frequency from being exceeded. Thus, stable operation without stalling or damage to the inverter elements is achieved regardless of the voltage/frequency ratio set to drive the motor or the particular induction motor used.
20 Citations
7 Claims
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1. In a control apparatus for an inverter wherein an A.C. power source is subjected to variable-frequency and variable-voltage conversion to drive an induction motor at a variable-speed;
- an inverter control apparatus comprising;
a first current level setting unit (5) for establishing a predetermined current level within a permissible limit of switching elements disposed in the inverter, a second current level setting unit (7) for establishing a current level at a slip value corresponding to a stall torque, in association with a characteristic of the loaded induction motor and an output voltage/output frequency ratio, a current level selector (8) for selecting the smallest one of the output signals of said first and second current level setting units, a current detector (4) for detecting the inverter output current, and control means (6) for controlling the switching elements in response to a velocity command, the output of the selected current level setting unit, and the detected inverter output current to render the inverter output current smaller than the selected current level signal. - View Dependent Claims (2, 3, 4, 5, 6, 7)
- an inverter control apparatus comprising;
Specification