Power supply system and power supply method

A power supply system, provided with a high voltage system and a low voltage system, comprising:

• an a.c. motor that is a load on the high voltage system and is driven by a high voltage power source;
• an inverter for controlling supply of power to the a.c. motor;
• a low voltage system supply path for applying a neutral point voltage of the a.c. motor to a load of the low voltage system;
• a load of the low voltage system for connecting to the low voltage system supply path, wherein a voltage ratio of the low voltage system to the high voltage system is set to from 1:2 to 1:4;
• a relay for opening and closing the low voltage supply path;
• and
• determining means for determining whether or not inverter control for making the voltage ratio a specified value is appropriate, wherein if it is determined by the determining means that control is inappropriate, the relay is opened,
• wherein when opening or closing the relay, a motor output command is changed so as to control a.c. motor output variations attributable to variations in neutral point voltage based on opening and closing of the relay.

A power supply system, provided with a high voltage system and a low voltage system, comprising:

• an a.c. motor that is a load on the high voltage system and is driven by a high voltage power source;
• an inverter for controlling supply of power to the a.c. motor;
• a low voltage system supply path for applying a neutral point voltage of the a.c. motor to a load of the low voltage system;
• a load of the low voltage system for connecting to the low voltage system supply path, wherein a voltage ratio of the low voltage system to the high voltage system is set to from 1:2 to 1:4;
• a relay for opening and closing the low voltage supply path;
• and
• determining means for determining whether or not inverter control for making the voltage ratio a specified value is appropriate, wherein if it is determined by the determining means that control is inappropriate, the relay is opened,
• wherein, when opening or closing the relay, the relay is opened or closed after controlling the neutral point voltage to zero.

A power supply system, provided with a high voltage system and a low voltage system, comprising:

• an a.c. motor that is a load on the high voltage system and is driven by a high voltage power source;
• an inverter for controlling supply of power to the a.c. motor;
• a low voltage system supply path for applying a neutral point voltage of the a.c. motor to a load of the low voltage system;
• a load of the low voltage system for connecting to the low voltage system supply path, wherein a voltage ratio of the low voltage system to the high voltage system is set to from 1:2 to 1:4;
• a relay for opening and closing the low voltage supply path;
• and
• determining means for determining whether or not inverter control for making the voltage ratio a specified value is appropriate, wherein if it is determined by the determining means that control is inappropriate, the relay is opened,
• the power supply system having a current return diode, connected from the low voltage system to the high voltage system, for returning power from the low voltage system to the high voltage system.