Albright International Coil Ratings Terminology

Wednesday, 26 July 2017  |

Operating Coils

 Coil voltages ranging from 6 to 240v are available, which are wound for D.C. operation. However, the majority of coils can be fitted with a bridge rectifier for use with A.C. supplies. Coils are wound with pull-in voltages (coils at 20°C) approximately 66% of the rated voltage (Continuous) or 60% (Prolonged, Intermittent Or Very Intermittent), and drop-out voltage nominally greater than 10% of the rated voltage. Variations from these pull-in and drop-out figures can be engineered to suit particular applications.


Continuous (CO)

 100% duty cycle. Continuous operation. Weakest power coil dictating that a weaker, when compared to the intermittent equivalent, return spring is used. This does not give the best switching characteristics for applications switching frequently on load.

Prolonged (PO)

 Up to 90% duty cycle, up to 54 minutes continuous energisation. The coil is more powerful than continuous and weaker than intermittent equivalent. The return spring is stronger than continuous but weaker than intermittent.

Intermittent (INT)

 Up to 70% duty cycle, up to 15 minutes continuous energisation. High power in coil allowing strong return spring to be used, giving good switching characteristics. Typically this rating is used with magnetic latching contactors.

Highly Intermittent (HO)

 Up to 25% duty cycle, up to 3 minutes continuous energisation. Highest power in coil allowing strongest return spring to be used, giving good switching characteristics.