A power transforming apparatus for supplying power to a magnetic bearing-applied motor , the apparatus comprising: an inverter ; an inverter controller connected to the inverter and configured to control an operation of the inverter ; a converter ; a magnetic bearing controller connected to the converter ; a step-down transformer to step down a three-phase alternating-current, AC, input voltage to supply an alternating-current, AC, stepped-down first power to the converter through a first branch line and to supply the AC stepped down first power to an auxiliary circuit through a second branch line upon an initial operation, an auxiliary circuit configured to perform charging of the auxiliary circuit using the first power and to supply rectified second power to the inverter controller and the magnetic bearing controller through a relay located between the converter and the auxiliary circuit , said relay being turned on or off by the converter , wherein the converter is adapted to receive the first power through the step-down transformer upon the initial operation, wherein the inverter controller is configured to output a driving signal to the inverter using the second power, and to control the inverter to supply a rectified direct-current, DC, voltage to the converter upon the initial operation, wherein the converter is configured to cut off the supply of the second power by turning off the relay and to control the rectified DC voltage to be supplied to the inverter controller and the magnetic bearing controller during a normal operation, wherein the converter is configured to supply a regenerative voltage during a power failure, and wherein the converter is configured to output a control signal by turning on the relay so that the second power of the auxiliary circuit is supplied to the inverter controller and the magnetic bearing controller upon a fault of the converter . an inverter ; an inverter controller connected to the inverter and configured to control an operation of the inverter ; a converter ; a magnetic bearing controller connected to the converter ; a step-down transformer to step down a three-phase alternating-current, AC, input voltage to supply an alternating-current, AC, stepped-down first power to the converter through a first branch line and to supply the AC stepped down first power to an auxiliary circuit through a second branch line upon an initial operation, an auxiliary circuit configured to perform charging of the auxiliary circuit using the first power and to supply rectified second power to the inverter controller and the magnetic bearing controller through a relay located between the converter and the auxiliary circuit , said relay being turned on or off by the converter , wherein the converter is adapted to receive the first power through the step-down transformer upon the initial operation, wherein the inverter controller is configured to output a driving signal to the inverter using the second power, and to control the inverter to supply a rectified direct-current, DC, voltage to the converter upon the initial operation, wherein the converter is configured to cut off the supply of the second power by turning off the relay and to control the rectified DC voltage to be supplied to the inverter controller and the magnetic bearing controller during a normal operation, wherein the converter is configured to supply a regenerative voltage during a power failure, and wherein the converter is configured to output a control signal by turning on the relay so that the second power of the auxiliary circuit is supplied to the inverter controller and the magnetic bearing controller upon a fault of the converter . <EOS>