Noise filter

A noise filter provided on an electric path connecting an AC power supply, a load supply, and a power conversion device which converts AC power outputted from the AC power supply and outputs the converted AC power to the load, the noise filter comprising:

• a noise detection circuitry which detects a common mode noise flowing through the electric path;
• a cancellation signal generation circuitry which, on the basis of the common mode noise detected by the noise detection circuitry, generates a cancellation signal for canceling out the common mode noise;
• an injection circuitry which injects the cancellation signal into the electric path;
• an abnormality detection circuitry which detects abnormality of the noise filter on the basis of output voltage or output current of the cancellation signal, and outputs an abnormality detection signal;
• and
• protection circuitry which inhibits the cancellation signal that is abnormal from being injected into the electric path, on the basis of the abnormality detection signal.