IEC 60034-11-2020 pdf download.Rotating electrical machines — Part 11: Thermal protection
Machines electriques tournantes — Partie 11: Protection thermique.
3.4
thermal protector
electrically insulated device that is sensitive to the temperature of the machine winding which carries machine current, capable of directly switching off the machine when its temperature reaches a predetermined level
Note 1 10 entry: Some thermal protectors are sensitive to both temperature and current, the combrnation of which activates the direct switching off of the machine.
3.5
thermal overload with slow variation
overload condition or loss of cooling that produces a rise of temperature that is sufficiently slow that the temperature of the thermal protector or detector follows it without appreciable delay
3.6
thermal overload with rapid variation
overload condition or loss of cooling that produces a rise of temperature that is too rapid for the
temperature of the thermal protector or detector to follow without appreciable delay resulting in
a significant temperature difference between the thermal device and the part to be protected
3.7
maximum temperature after tripping
maximum value of the temperature that is reached by the protected part of the machine during the period which follows tripping by the thermal protection system
3.8
direct thermal protection
form of protection where the part of the machine in which the thermal detector(s) or thermal protector(s) are incorporated is the part for which protection is being provided
3.9
indirect thermal protection
form of protection where the part of the machine in which the thermal detector(s) or thermal protector(s) are incorporated (e.g. the stator winding) is not the part for which protection is being provided (e.g. the rotor winding)
4 Thermal protection limits
Machines shall be capable of operating at rated output and at all operating conditions according to IEC 60034-1 without activation of the thermal protection device. The thermal protection device shall limit the winding temperature in accordance with Clause 5 or Clause 6.
7 Restart after tripping
Before restarting a machine that has tripped, an investigation shall be made to try to Identify the cause of the operation of the machine protection. When attempting to restart the machine. account shall be taken of the conditions stated in 6.3 or 9.3 of IEC 60034-12:2016.
The methods of protection included in this document only protect rotor windings indirectly. For large motors (particularly 2 pole motors) and for motors starting large inertia loads, special attention needs to be given to rotor heating both when starting and especially after a “trip has occurred.
NOTE The provision of the facility to enable machines to be automatically restarted after tripping is a matter for special agreement taking full account of all safety implications.
8 Type tests
8.1 General
Type tests are to verify the compliance of a thermal protection system with the requirements of this document.
Tests shall be made on a machine which is representative of the machine type. The proposed thermal protection system shall be installed.
Temperature sensors used for testing shall be located in positions representative of the location of the thermal detectors used by the thermal protection system.
8.2 Verification of temperature due to the thermal overloads with slow variation Starting with the machine at operating temperature, the load shall be slowly increased so that the temperature of the winding increases at a rate of less than 1 K per 5 mm. Temperatures shall be recorded at a minimum of 10 mm Intervals.
When the thermal protection system trips, the supply to the machine shall be switched off if it is not directly interrupted by the thermal protection device. The winding temperature shall be determined immediately after tripping in accordance with the requirements of 8.6.2 of
IEC 60034-1:2017.
The winding temperatures specified in Table 1 shall not be exceeded.
8.3 Verification of temperature due to thermal overloads with rapid variation
Verification of the temperature Is required only in cases where a motor is protected by built-in positive temperature coefficient thermistors (PTC) or via a thermostat and where it is not protected by a thermal protection device.
Starting with the machine at ambient temperature, with the rotor locked to prevent rotation, apply rated voltage to the windings. At the end of the energised period, the maximum temperature of the winding shall be recorded. For manual re-set systems, the protector shall be re-closed as quickly as possible and power restored.
Protection systems with automatic resetting shall be operated for a minimum of 10 cycles, unless the change in peak temperature between two cycles is below 5 K.
The highest temperature attained shall not exceed the values in Table 2.
9 Routine tests
Devices used for thermal detection shall be tested for circuit continuity to assure that no damage has occurred during installation.IEC 60034-11-2020 pdf download.Rotating electrical machines