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D
Dust Shields The aperture usually found in the top cover housing is sealed to form a barrier to assist prevention of airborne contamination into the contact area.
Duty An explanation on the terminology used to describe the coil ratings is detailed below:
Very Intermittent - Up to 25% duty Cycle, up to 3 minutes continuous energisation. Very intermittent - Highest power in coil allowing strongest return spring to be used, giving good switching characteristics available.
Intermittent - Up to 70% duty cycle, up to 15 minutes continuous energisation. Intermittent - High power in coil allowing strong return spring to be used, giving good switching characteristics available.
Prolonged - Up to 90% duty cycle, up to 54 minutes continuous energisation. Prolonged - Coil; more powerful than continuous, weaker than intermittent equivalent. Return spring is stronger than continuous but weaker than intermittent
Continuous - 100% duty cycle. Continuous operation. Continuous - 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.
Duty Cycle The on period over the total cycle, supplied as a percentage. duty cycle = D t = on time (coil energised)
T = Total cycle time (on time + off time)

where
D is the so-called duty cycle; t is the duration that the function is non-zero;
Τ is the period of the function.
Drop Out Voltage The voltage (V) required to open the contacts (on a normally open contactor) at 20 degree Celsius.
Double Pole (DP) Contact configuration – two sets of single pole contacts
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