Precharge control apparatus

A precharge control apparatus comprising:

• a main contactor provided in a power supply path from a battery to a load;
• a smoothing capacitor connected in parallel to the load;
• a precharge contactor connected in parallel to the main contactor via a current limiting resistor;
• a voltage sensor configured to detect a battery voltage of the battery and a capacitor voltage of the capacitor;
• and
• a controller configured to
• start a precharge of the capacitor by closing the precharge contactor,
• determine that the precharge of the capacitor is completed in response to that a set time has elapsed from when a voltage difference between the battery voltage and the capacitor voltage detected by the voltage sensor becomes equal to or less than a set voltage, and
• close the main contactor upon determining that the precharge of the capacitor is completed,
• the set voltage being set based on a maximum error obtained by adding a maximum value of a detection error of the battery voltage by the voltage sensor and a maximum value of a detection error of the capacitor voltage by the voltage sensor,
• the set time being set based on a time from when the voltage difference becomes twice the maximum error to when the voltage difference becomes equal to or less than a withstand voltage of the main contactor, under a state where the precharge causes the capacitor voltage to increase with a time constant when a resistance value of the current limiting resistor and a capacitance of the capacitor each are largest within an allowable error.