A filter appliance comprises first electrical terminals (201-203) for connecting to a multiphase electrical converter device, second electrical terminals (204-206) for connecting to a load, main current coils formed of foil conductors and connected between the first and the second electrical terminals, and shielding coils whose first ends are electrically connected to a third electrical terminal (219) of the filter appliance. Each of the shielding coils is formed of foil conductor that is alongside and a distance apart from the foil conductor of the corresponding main current coil so as to form a capacitive shield between successive turns of the main current coil. When the third electrical terminal is connected to constant electrical potential, the shielding coils reduce the common mode voltage applied to the load and, for example, a risk of bearing damages in an electrical motor driven by a multiphase electrical converter device is reduced.