The STAMFORD® UC27 has a maximum continuous rating of 313kVA at 60Hz (250kVA at 50Hz) and a voltage output of 380-690 volts.he STAMFORD® UC27 alternator’s proven and robust design allows it to be used for applications such as grid code, combined heat and power, marine, mobile construction, utility works and telecom industry. The UC27 product is offered only as a 4 pole alternator.