The present invention relates to an X-ray apparatus comprising an X-ray tank including an X-ray tube for outputting an X-ray and an X-ray main body, which provides the X-ray tube with tube voltage and tube current. The X-ray main body comprises: a power supply unit for providing the X-ray main body with operating power by receiving electric power from commercial AC power supply a control unit for receiving the operating power from the power supply unit and controlling the X-ray main body and a driving unit for providing the X-ray tube with tube voltage and tube current according to the control signal received from the control unit. The control unit comprises a derating module for performing a control in a derating mode in case where at least one of tube voltage and tube current provided to the X-ray tube is smaller than the first voltage threshold value or the first current threshold value or greater than the second voltage threshold value or the second current threshold value. The derating mode is configured to control the tube current and driving time so that the X-ray apparatus operates for 2 hours, which is longer than 1 hour and is the driving time under the rated current, which is the tube current that is lower than the rated current. The present invention is designed to provide an X-ray apparatus and a method of derating the X-ray apparatus capable of preventing an unnecessary radiation exposure to a human body occurred when an X-ray apparatus stops by continuously operating the X-ray apparatus even in case where power supplies from commercial AC power lines are not enough.COPYRIGHT KIPO 2016본 발명은 엑스레이를 출력하기 위한 엑스레이 튜브를 포함하는 엑스레이 탱크 및 상기 엑스레이 튜브에 관전압 및 관전류을 공급하는 엑스레이 본체를 포함하는 엑스레이 장치에 있어서, 상기 엑스레이 본체는, 상용 AC 전원으로부터 전력을 입력받아 상기 엑스레이 본체에 동작 전원을 제공하기 위한 전원부 상기 전원부로부터 동작 전원을 공급받고 상기 엑스레이 본체를 제어하기 위한 제어부 및 상기 제어부로부터 수신된 제어신호에 따라 상기 엑스레이 튜브에 관전압 및 관전류을 공급하는 구동부를 구비하고, 상기 제어부는 상기 엑스레이 튜브에 공급된 관전압 및 관전류 중 적어도 하나가 제1 전압 입계값 또는 제1 전류 입계값보다 작거나 제2 전압 임계값 또는 제2 전류 임계값보다
