Amcot ST Series - Mechanical System - Motors; Motors - General Information

AMCOT ST SERIES FIBERGLASS COOLING TOWER
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GENERAL MAINTENANCE
Mechanical System – Motors
Motors – General Information
Amcot fan motors are designed specifically for use on the ST Series cooling tower. Most of the ST Model
towers ST-3 to ST-200 are direct drive motors, meaning the fan is directly secured to the motor’s output
shaft. As a result, these motors use custom output shafts which are specific to Amcot towers/motors.
For ST Models ST-225 and greater, the motor uses a standard output shaft that corresponds with the
NEMA frame for that motor HP. The mechanical assembly for these units utilize a housed belt reducer
to regulate fan speed in relationship to motor RPM.
All of Amcot’s ST Series motor are UL/CSA Recognized and have an IP55 Enclosure which means they are
sealed and will not allow water or moisture to reach the internal components. These motors are
designed specifically for harsh environments because of the moisture and chemicals that they may be
exposed to when in operation.
Many towers are now operated on a variable frequency drive (VFD) or variable speed drive (VSD) control
system to regulate motor speed based on cold water temperature. This offers owners the ability to
minimize energy use by allowing the motor to run at speeds of less than 100%. Most motors are what is
known as inverter duty rated which simply means they can be used in conjunction with such drives and
the owners do not risk damaging the motor.
For Models ST-30 to ST-1500 the motors supplied are inverter duty rated which means they can be
operated in conjunction with a VFD or VSD driver (sold separately). In doing so however the frequency
range for the motor is 20-60 Hz. Frequencies below 20% must be locked out on the VFD/VSD, otherwise
you will damage the motor and cause failure to occur.
For models ST-H-3 to ST-25, the fractional horsepower motors used on these units are not inverter duty
rated. Therefore it is recommended that you do not use a VFD or VSD on these models.
For models ST-H-3 to ST-25, it is recommended that you would incorporate an alternate form of fan
motor control such as a standard on/off temperature controller that monitors cold water basin
temperature and cycles the motor on/off based on temperature settings programmed into the device.
Amcot motors are available in a wide range of electrical configurations. However for most markets we
have standardized electrical specifications for our motors as follows:
ST-H-3 to ST-H-20-1 Single Phase, 110/220v, 60 Hertz
ST-H-20-3 to ST-1500 Three Phase, 208-230/460v, 60 Hertz
Motors should always be operated at or slightly below (within 10%) of the amp draw specified on the
motor nameplate for the indicated voltage. Operation that exceeds nameplate voltage will permanently
damage the motor. If Amp draw is too high, check for fill or air obstructions or decrease fan blade
angles per fan adjustment instructions on pages 31-33.