The IET is carrying out some important updates between 17-30 April and all of our websites will be view only. For more information, read this Announcement

Rules and Guidelines
Want to participate in the discussions? Please read our Community Rules and Guidelines. Need some help? Visit Support and Answers.

  • State Not Answered
  • Locked Locked
  • Replies 4 replies
  • Subscribers 34 subscribers
  • Views 3111 views
  • Users 0 members are here
Options
You may also be interested in
This discussion is locked.
You cannot post a reply to this discussion. If you have a question start a new discussion

552.1.2 motor overload requirements

E95

Hi all,

Currently have a motor incorporated into a fan oven, however the only electrical protection on the power circuit is an MCB. to a contactor.

552.1.2 states:

"Every electric motor having a rating exceeding 0.37kW shall be provided with control equipment incorporating means of protection against overload of the motor. This requirement does not apply to a motor incorporated in an item of current using equipment complying as a whole with an appropriate British or harmonised standard"

Annex A53, table TA53.1 says that a circuit provides overload protection

Is this all the standard wants, an MCB with the thermal overload component? Or is it talking about a separate overload relay added on to the contactor? Obviously a 10A MCB won't begin to operate until current is 14/15A

Thanks

Parents
  • 0

    Ah, then it is more complex, and will indeed depend on what  the design authority of the equipment intended (I presume they did not CE mark it..). Basically something needs to shut the motor off before it catches fire, and if it is not something inside  the motor, then it needs to be a starter with a time lag overload protection built in, as any normal fuse, when set hihg enough to not blow as a false alarm on the start up inrush, is probably not fine enough to reliably blow if the motor overheats.

    Large motors have an unfavorable inrush to overload ratio.

    mike.

Reply
  • 0

    Ah, then it is more complex, and will indeed depend on what  the design authority of the equipment intended (I presume they did not CE mark it..). Basically something needs to shut the motor off before it catches fire, and if it is not something inside  the motor, then it needs to be a starter with a time lag overload protection built in, as any normal fuse, when set hihg enough to not blow as a false alarm on the start up inrush, is probably not fine enough to reliably blow if the motor overheats.

    Large motors have an unfavorable inrush to overload ratio.

    mike.

Children
No Data

Join us to get the best from IET EngX.

Joining EngX lets you personalise your experience so you stay up to date on the topics that interest you, plus you’ll be able to make connections who are looking to collaborate, exchange ideas and more.

Join us Not now

Community Rules & Guidelines