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IEC Contactors

  1. Feb 19, 2009 #1
    Can someone explain to me what a 3 phase IEC Contactor/starter is, how it works, and what its used for? Thanks
  2. jcsd
  3. Feb 20, 2009 #2


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    A contactor is basically a really high-current version of a relay:

    Suitable, for, say, handling the current required to start a motor. (Although some quick googling indicates that a contactor / starter, as manufactured by a number of companies, is a self-contained unit that allows you to engage the contactor).

    IEC (International Electrotechnical Commission) is a standards body, similar to NEMA (National Electromechanical Manufacturers Association):

    So it's most likely a 3 pole single throw switch / relay (switches all three phases)
  4. Feb 20, 2009 #3
    Thanks, for some reason I was thinking capacitor since it said starter.
  5. Feb 21, 2009 #4
    The large number of IEC contactor sizes allows you to more closely match the contactor to the load or application. Unlike NEMA, where the available sizes are standard across the industry, the number of different contactor size ratings varies by manufacturer.
    Generally, an IEC starter is about half the size of a comparable NEMA starter. Above 100A (NEMA Size 3), however, the physical differences between NEMA and IEC are negligible.
    IEC products are more modular in nature; they can snap onto a 35-mm, or in larger sizes, a 75-mm DIN rail. This eliminates the need to drill holes and mount each component individually. Thus, putting them into a panel is relatively easy.
    Unlike NEMA starters, which typically are sold fully assembled, IEC starters typically are sold as components (a contactor, an auxiliary block, an overload relay block) so that you can make your own assembly. You simply select the accessories needed for the application and snap them together, without the use of tools.
    Also unlike NEMA starters, IEC-style thermal overload relays typically have fixed thermal elements, with an adjustment range that may require replacing the complete overload relay when significant motor FLC changes due to application requirements.
    A large number of IEC contactors are applied in group installations, and NEC Sec. 430-53 deals with this application facet. However, this isn't unique to IEC contactors, since you can install any starter this way.
    IEC products, more often than not, are sold to OEMs, which typically install them in applications where multiple devices are needed to control different functions of a machine.
    Type 2 coordination is an IEC standard that can be applied to a NEMA-style product as well. Type 2 protection is afforded by the use of a properly rated and class of fuse with a contactor or starter. This type of protection requires that, after short-circuit condition testing, the contactor or starter must be reusable without component or part replacement. Also, no significant change is allowed in the operating time-current characteristics of the overload relay. This is a coordinated protection standard for the short-circuit protective device, contactor, and overload relay. The rules are the same for both IEC- and NEMA-style devices. For Type 2 coordination, the typical higher withstand rating of a NEMA-style starter provides a greater selection of short-circuit protective devices. Type 2 coordination with IEC-style products will offer the same coordination and degree of protection; however, the selection of fuse classes may be more limited. For short-circuit currents up to 5000A, Type 2 protection for IEC-rated motor starters would require Class RK5, J, RK1, or CC fuses. For short-circuit currents up to 100kA, Class RK1, J, and CC fuses are required.
    Compared with NEMA-style products, IEC-style products are more disposable than serviceable. In fact, IEC products below 100A typically are considered disposable; they can be removed from a DIN rail, thrown away, and replaced with a new product in a matter of minutes.
    Self protected starters represent a new category of combination starters as defined in UL 508-E. Typically, such a starter has a contactor, an overload relay, and short-circuit protection. The device also undergoes a unique testing procedure, one that goes beyond that for conventional combination motor controllers. This procedure tests the starter at different fault levels, verifying that coordinated protection similar to Type 2 is provided.


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  6. Feb 21, 2009 #5


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