Difference between AC3 and AC4 Duty Contactors
from the above table it is clear that since crane have many inching operations hence AC4 duty contactors
should be selected.
should be selected.
Why Derating of contactors is required
The catalog contactors with AC4 DUTY have an electrical life. For a Crane application the contactors
should be suitable for atleast 200000 cycles unless specified elsewhere. Each manufacturer of
contactor gives an electrical life curves chart.
should be suitable for atleast 200000 cycles unless specified elsewhere. Each manufacturer of
contactor gives an electrical life curves chart.
For example, Consider MO32 Power Contactor. The rated AC-4 current of MO32 is 32A.
The Electrical life of MO 32 at 32A AC-4 is 50000. When a 32A contactor is used for 32A AC-4 application,
one gets an operation life of 50000 operating cycles. If the contactor does approximately 500 switching
cycles per week then the contactor will last for a period of 50000/500 = 100 weeks i.e. roughly 2 Years.
one gets an operation life of 50000 operating cycles. If the contactor does approximately 500 switching
cycles per week then the contactor will last for a period of 50000/500 = 100 weeks i.e. roughly 2 Years.
Below is the selection table of contractors for 200000 operating cycles
For example, if one wants 200000 operating cycles for the rated current of 9A AC-4 then
contactor selected should be MO 25.
contactor selected should be MO 25.
