Page 156 of Current Catalog by Moeller Electric USA

03/074 contactors selection guide contactors by far the most common application of contactors is the control of electrical motors as a prime mover the 3-phase ac motor in particular the squirrel-cage motor dominates the field and most of them are controlled by contactors contactors are expected to start stop reverse plug jog and sequence motors and in conjunction with overload relays to protect motors in the event of overloads the load rating stated in hp is the basic data required to enable the correct selection of contactors to be made but this figure by itself is not always sufficient the type of load its operating cycle switching frequency and total life required all influence the overall stress on contactors the electrical durability tests of contactors outlined in appendix b of iec 60 947-4 are used by manufacturers to establish contactor ratings which incorporate a sufficient and verifiable normal switching duty ac-3 for squirrel-cage motors operating characteristics typical applications switching capability to cover a broad range of applications as defined in the iec utilization categories e.g ac-3 ac-4 the iec 60 947 standard states that with respect to its resistance to electrical wear a contactor or starter is by convention characterized by the number of on-load operating cycles corresponding to the different utilization categories which can be made without repair or replacement the iec utilization categories ac-3 and ac-4 are most often encountered in contactor applications and are outlined below see section 14 of this catalog for additional details the curves at right provide a reliable guide for selection based on the electrical life desired magnetic contactors magnetic starters starting from rest stopping after attaining full running speed mixers elevators compressors agitators escalators pumps centrifuges conveyors fans bucket elevators airconditioning valves drives in general in manufacturing and processing machines electrical characteristics make up to 6 x rated motor current break 1 x rated motor current utilization category 100 ac-3 operating characteristics typical applications switching plugging reversing printing presses wire-drawing machines centrifuges special drives for manufacturing and processing machines extreme switching duty ac-4 for squirrel-cage motors electrical characteristics make 6 x rated motor current break 6 x rated motor current utilization category 100 ac-4 determination of the maximum number of operations per hour in relation to rating and utilization category pn max motor rating kw/hp of the contactor a pages 03/002 003 s/h max number of operations per hour type s/h 9000 6000 5000 4000 3000 ac-1 2 2 2 2 2 2 2 2 2 ac-3 1 1 1 1 1 1 1 1 1 ac-2 ac-4 3 3 3 3 3 3 3 3 3 2000 1500 1000 800 600 500 400 300 200 150 100 0 10 20 30 40 50 60 70 80 90 100 n [kw dil em dil 00 m g dil 00 am g dil 0 m g dil 0 am g dil 1 m g dil 1 am g dil 2 m g dil 2 am g type s/h 9000 6000 5000 4000 3000 1 2000 1500 2 3 ac-1 1 1 1 1 1 2 2 2 2 2 2 ac-3 1 1 2 2 2 3 3 3 3 3 3 ac-4 4 4 5 5 5 6 6 6 6 6 6 1000 800 700 600 500 400 300 200 150 100 0 10 4 5 6 dil 3m 80 dil 4m 115 dil m 185 dil m 225 dil m 250 dil m 300 dil m 400 dil m 500 dil m 650 dil m 750 dil m 820 20 30 40 50 60 70 80 90 100 pn[kw]

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