What precautions should be observed when applying reduced voltage starting to a load with rising characteristic such as fans?

If the specified starting current is too low, the motor may start correctly but not run fully up to speed. The result is that on changing over to the running or full-voltage condition a very high current may be taken, thus negating the low initial current. For this reason, even with fan drives, it is not desirable to pin the starting current lower than about 200 percent of full-load current.