Automatic circuit breaker testers UPA are intended for automatic AC current circuit breakers testing. The devices allow registering the values of the supplied current and timing the automatic circuit breaker switching interval. UPA operate on the principle of varying the power in the primary circuit of the matching power transformer and, respectively, varying the output current, flowing through the
automatic circuit breaker under the test. Power regulation could be done either through an external voltage regulator
(RNO or VR) or through a built-in thyristor controller.
All metrological characteristics (current and time measurement) are valid if RNO is used, i.e. if the exit signal waveform is stable (just as in other analogs).