This part of IEC 60947 series specifies requirements for control units, which control a switching device in response to the PTC thermistors incorporated in rotating electrical machines and the industrial application.

It specifies requirements for that type of system comprising a positive temperature coefficient (PTC) thermistor having particular characteristics, and its associated control unit.

This document includes:
- the characteristics, construction, performance and tests of the control unit; and
- its association with a PTC thermistor designated Mark A.

This document does not cover:
- the incorporation of thermal protections into rotating machines and their maximum winding temperature. See IEC 60034-11;
- use of the product within explosive atmospheres (see IEC 60079 (all parts));
- software and firmware requirements;
NOTE 1 Guidance on embedded software is given in IEC TR 63201.
- cyber security aspects (see IEC TS 63208).

NOTE 2 It is not possible to specify all the requirements for the operating characteristics of a control unit, as they are dependent on some aspects of the PTC thermistors. Some aspects of the requirements of the thermal protector system can only be specified when account is taken of the characteristics of the rotating machine to be protected and the method of installation of the PTC thermistor within the machine.