What is the application of Frequent start protection N> (66) in VAMP 255/245/230 relays.
Frequent start protection N> (66):
The simplest way to start an asynchronous motor is just to switch the stator windings to the supply voltages. However every such start will heat up the motor considerably because the initial currents are significantly above the rated current.
If the motor manufacturer has defined the maximum number of starts within on hour or/and the minimum time between two consecutive starts this stage is easy to apply to prevent too frequent starts.
When the current has been less than 10% of Imot and then exceeds Ist>, the situation is recognized as a start.
When the current is less than 10 % of Imot, the motor is regarded as stopped.
The stage will give a start signal when the second last start has been done. The trip signal is normally activated and released when there are no starts left.