Eaton Cutler-Hammer MP1 Series Instructions Manual

Page 4 I.L.15.01.T.K.Effective June 20003.3 Description of OperationThe Cutler-Hammer Automatic TransferSwitch provides automatic transfer of anelectrical load to a standby power supply inthe event of drop or loss of voltage of any orall phases of the normal power supply. Uponthe restoration of the normal supply, theelectrical load is automatically retransferredto the normal power supply. The mechanismprovides a positive mechanical interlock toprevent both breakers being closed at thesame time. The mechanism is also designedto leave both breakers trip free in the closedposition, permitting incorporation of thermaland short-circuit protection in either or bothbreakers. In Type B switches, an alarmswitch contact is supplied. This contact isconnected to the controller to lock the motorcircuit out of operation when the breaker(s)trip on an overload or short-circuit condition.Then the breaker has to be manually reset.Instructions for the reset procedure arelocated on the front of the operatingmechanism.3.4 DefinitionsWith respect to their use in this documentand as they relate to automatic transferswitch operation, the following terminology isdefined:Available – A source is defined as“available” when it is within all undervoltage /overvoltage / underfrequency /overfrequency setpoint ranges for thenominal voltage and frequency setting.Fails – A source is defined as “failed” whenit is outside of any undervoltage /overvoltage / underfrequency /overfrequency setpoint ranges for thenominal voltage and frequency setting for atime exceeding 0.5 seconds.Failsafe – Refers to the condition wherebythe transfer switch is connected to theemergency source. In the event that theemergency source fails with normal sourceavailable an immediate retransfer to normalsource shall occur.Transfer – A “transfer” is defined as theautomatic operation under a normal sourcefailure of switching the Load from NormalSource to the Emergency Source.Retransfer – A “retransfer” is defined as theautomatic operation under Normal Sourcereappearance of switching the Load fromEmergency Source to Normal Source.