Noise filter

A noise filter of an electrical device connected to an AC power supply having a first electrode connected to a power supply ground and a second electrode not connected to the power supply ground, the noise filter comprising:

• a first power supply line connected to one of the first electrode and the second electrode;
• a second power supply line connected to the other of the first electrode and the second electrode;
• a first Y capacitor connected to the first power supply line;
• a second Y capacitor connected to the second power supply line;
• a first relay connected between the first V capacitor and an electrical device ground;
• a second relay connected between the second Y capacitor and the electrical device ground;
• a ground-side power supply line detecting circuit that is connected to each of the first power supply line and the second power supply line, and detects a power supply line connected to the first electrode from among the first power supply line and the second power supply line;
• and
• a control circuit to determine whether a power supply line connected to the first electrode is the first power supply line or the second power supply line on a basis of a detection result by the ground-side power supply line detecting circuit, controls the first relay to short-circuit between the first Y capacitor and the electrical device ground when determining that the power supply line connected to the first electrode is the first power supply line, and controls the second relay to short-circuit between the second Y capacitor and the electrical device ground when determining that the power supply line connected to the first electrode is the second power supply line.