Minimum/maximum excitation limiter performance goals for small generation

Small generators connected to the utility system often act as followers as they tend to follow system bus voltage variations. For the lack of kVA capacity, small machines tend to be susceptible to becoming over or under excited (excessive Vars in or Vars out of the generator) as the voltage regulator tries to maintain its setpoint with variations in system bus voltage. Minimum and maximum excitation limiters are utilized to limit the voltage regulator characteristic response to system bus voltage changes, that can otherwise result in machine overheating and/or pulling out of synchronization. This paper reviews the operating performance of minimum and maximum excitation limiters used on small machines, and provide the user typical performance expectations. The examples will highlight both main field and exciter field applications. Lastly, conditions will be reviewed that may occur during excitation limiter initial startup that can affect their ability to be initially tuned.