Mechanical load test
If the LTC is operated by a separate motor-drive mechanism, the output shaft shall be loaded by the largest LTC for which it is designed or by an equivalent simulated load.
At such a load, 500 000 operations shall be performed at room temperature across the entire tap range. Additional cooling of the motor-drive is permissible during this test.
During this test, 10 000 operations shall be performed with the motor supply voltage at 85% of rated drive motor voltage. Also, 10 000 operations shall be performed at 110% of rated drive motor voltage. In addition, 100 operations shall be performed at a temperature of -25 °C.
The correct functioning of the tap position indicator, limit switches, restarting device, and operation counter shall be verified during this test. At the completion of this test, the LTC shall be operated manually, if applicable, through one cycle of operation.
The test shall be considered to be successful if there is no mechanical failure or any undue wear of the mechanical parts. Normal servicing according to the manufacturer's instruction book is permitted during the test. During this test, the heating system of the motor-drive mechanism shall be switched off.
Overrun test
It shall be demonstrated that, in the event of a failure of the electrical limit switches, the mechanical end stops will prevent operation beyond the end positions when a motorized tap-change is performed and that the motor-drive mechanism will not suffer either electrical or mechanical damage.
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