Electric machine and power supply system having battery pack

A battery pack comprising:

• a first antenna for receiving electric power from a power supply source located outside by coupling with a first resonant magnetic field generated by the power supply source;
• at least one secondary battery charged by the electric power received by the first antenna;
• an oscillator for producing radio-frequency power by DC power discharged from the secondary battery;
• and
• a second antenna for generating a second resonant magnetic field by the radio-frequency power and magnetically coupling with a third antenna located outside.

A power supply system comprising:

• a battery pack for supplying electric power to a load;
• a first energy transfer section for transferring the electric power output from the battery pack to the load;
• and
• a second energy transfer section for transferring the electric power supplied from outside to the battery pack, wherein
• the battery pack includes:
• a first antenna for receiving electric power by coupling with a first resonant magnetic field generated by the second energy transfer section;
• at least one secondary battery charged by the electric power received by the first antenna;
• a first oscillator for producing first radio-frequency power by DC power discharged from the secondary battery;
• and
• a second antenna for generating a second resonant magnetic field by the first radio-frequency power;
• the first energy transfer section includes a third antenna that couples with the second resonant magnetic field generated by the second antenna;
• the radio-frequency power received by the third antenna is transferred to the load;
• and
• the second energy transfer section includes:
• a second oscillator for producing second radio-frequency power by using the electric power supplied from the outside;
• and
• a fourth antenna for generating the first resonant magnetic field by the second radio-frequency power.