Balanced synthetic circuit: new circuit for high-power testing with low-frequency transient recovery voltage

A new circuit is proposed for high-power synthetic tests of circuit-breaker performance. The new circuit is based on the current-injection principle, and is especially suited to economical tests with low-frequency transient recovery voltage (t.r.v.). Tests are possible with virtually any combination of t.r.v. and injection conditions, including those in which the t.r.v. frequency is lower than the injection frequency. The usual interaction which takes place between the t.r.v. and injection circuits is fully compensated, and, if necessary, components can be used in the t.r.v. network which are identical with those that would be used in a direct test under the same conditions. However, the usual restriction applies that there be no direct-current path to earth, if the recovery voltages is to be maintained. Examples are given of test circuits meeting the IEC requirements for the most difficult case of duty at 100% rated current.