1. An apparatus for delivering electrical power, in particular for delivering regeneratively produced electrical power to a load impedance, having at least one converter and at least one filter, characterised in that means for determining at least one filter current of at least one filter are provided, which are designed to allow a determination of the at least one filter current during operation of the apparatus, wherein comparison means are provided, which using the desired value and actual value of the filter current and a predefinable error criterion generate an error information signal, wherein as means for determining the at least one filter current a current sensor for measuring the current in only one phase or at least one current sensor for measuring the current in only two phases of the at least one filter are provided.