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When does the Drive Overheat Fault (OHF) occur in Altivar 71 Drives.

The Drive Overheat Fault (OHF) indicates that the heat sink temperature has crossed the temperature threshold. This is the information from the temperature sensor located on the heat sink, near the transistor module. When the Thermal Heat Dissipation (THD) is greater than 118% it trips in OHF. 118% is approximately 100 Deg Centigrade temperature on the heat sink. 

The main causes for the occurrence of this fault are:
1. Excessive ambient temperature. (Provide proper air cooling of the control room)
2. Fan air flow is blocked.
3. The minimum air clearance required around the Drive as indicated in the Installation Guide is not maintained.
4. Drive cooling fan not working.
(Check the LEDs on the Fan Supply Board. If LED 1 is off, then the fan is not working. If LED 2 is off then Fan Supply Board is out of order.)
5. The temperature sensor is faulty.
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