The units are fully compliant with NEMA AB-4 test guidelines. Tests are performed by simulating an overload or fault condition. Each test set is an integrated test system that provides a variable, high-current output. The test sets incorporate all control circuitry and instrumentation necessary to test direct-acting circuit breakers accurately, efficiently and safely. The unique transformer and circuit design results in a very high-capacity test set in a very compact size. Advanced digital control and instrumentation provides exact testing capacity.