Power conversion apparatus
AssigneeFuji Electric Co., Ltd.
InventorsHideki Oguchi, Akio Toba
Life of this patent
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Abstract
A controller for switching an inverter includes a current detecting unit, an overcurrent level determining unit which determines an overcurrent level for stopping the inverter in accordance with a value corresponding to the number of revolutions of a motor, a current comparing unit which compares a detected output current value of the inverter with the overcurrent level, and a gate signal generating unit which generates a signal for turning off all semiconductor switching devices of the inverter when the current comparing unit makes a determination that the detected output current value has reached the overcurrent level. The overcurrent level is lowered as the number of revolutions of the motor increases.
Claims19
A power conversion apparatus for driving an AC motor by using an inverter having a DC side to which a parallel circuit having a DC power supply and a capacitor is connected, wherein a controller for controlling semiconductor switching devices of the inverter includes:
- a current detecting unit which detects an output current of the inverter;
- an overcurrent level determining unit which determines an overcurrent level for stopping operation of the inverter in accordance with a value corresponding to a number of revolutions of the motor;
- a current comparing unit which compares a detected output current value of the inverter outputted from the current detecting unit with the overcurrent level determined by the overcurrent level determining unit;
- and
- a drive signal generating unit which generates a signal for turning off all the semiconductor switching devices of the inverter when the current comparing unit makes a determination that the detected output current value has reached the overcurrent level;
- wherein:
- the overcurrent level determined by the overcurrent level determining unit becomes lower in terms of value as the value corresponding to the number of revolutions becomes larger in a constant output region of the motor.
A power conversion apparatus for driving an AC motor by using an inverter having a DC side to which a parallel circuit having a DC power supply and a capacitor is connected, wherein a controller for controlling semiconductor switching devices of the inverter includes:
- a current detecting unit which detects an output current of the inverter;
- an overcurrent level determining unit which determines an overcurrent level for stopping operation of the inverter in accordance with a value corresponding to a number of revolutions of the motor;
- a current limit level determining unit which determines a current limit level for limiting the output current of the inverter in accordance with the value corresponding to the number of revolutions of the motor;
- a current comparing unit which compares a detected output current value of the inverter outputted from the current detecting unit with the overcurrent level determined by the overcurrent level determining unit, and which compares the detected output current value with the current limit level determined by the current limit level determining unit;
- and
- a drive signal generating unit which generates a signal for turning off all the semiconductor switching devices of the inverter when the current comparing unit makes a determination that the detected output current value has reached the overcurrent level, and which generates a signal for limiting the output current of the inverter at a certain phase when the current comparing unit makes a determination that the detected output current value has reached the current limit level;
- wherein:
- the overcurrent level determined by the overcurrent level determining unit and the current limit level determined by the current limit level determining unit become lower in terms of value as the value corresponding to the number of revolutions becomes larger in a constant output region of the motor.
An apparatus, comprising:
- a current detecting device configured to detect a current;
- and
- an overcurrent protection device configured to stop or inhibit an overcurrent condition based at least in part on the detected current and a motor speed;
- wherein the overcurrent protection device is configured to lower a threshold for determining that an overcurrent has occurred in response to an increase in the motor speed;
- and
- wherein the overcurrent protection device comprises:
- a comparison device configured to compare the detected current to a current threshold and output a comparison signal;
- and
- an overcurrent determination device configured to supply a range of current thresholds to the comparison device for comparison with the detected current;
- wherein values in the range of current thresholds decrease with increasing values of the motor speed.
Dependencies are inferred from the claim text.