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STF-R/C/D/IP Hardware Manual
920-0141 Rev. A
6/5/2018
2.7 Choosing A Power Supply
The main considerations when choosing a power supply are the voltage and current requirements of the application.
2.7.1 Voltage
The STF drive and motor is designed to give optimum performance between 24~48 Volts DC. Choosing the voltage
depends on the performance needed and diver/motor heating that acceptable and/or does not cause a drive over-
temperature. Higher voltage will give higher speed performance, but will cause the drive to produce higher temperatures.
Using power supplies with voltage outputs that are near the drive maximum may significantly reduce the operational
duty cycle.
STF03/06
The STF03/06 drive extended range of operation voltage can be as low as 11VDC minimum to as high as 53VDC
maximum. When operation below 11VDC, the STF03/06 series will work unstable. The supply input cannot go blow
11VDC for reliable operation, otherwise under voltage alarm will be triggered. STF03/06 drive will stop working when
this alarm is triggered.
If a regulated power supply is used, and that is near the driver maximum voltage of 53VDC ,a voltage clamp may be
required to prevent the voltage over 53VDC which will occurs a overvoltage fault. When using an unregulated power
supply, make sure the no-load voltage of the supply does not exceed the maximum input voltage 53VDC.
STF05/10
The STF05/10 drive extended range of operation voltage can be as low as 18VDC minimum to as high as 75VDC
maximum for STF10 and 53VDC maximum for STF05. When operation below 18VDC, the STF05/10 series will work
unstable. The supply input cannot go blow 18VDC for reliable operation, otherwise under voltage alarm will be triggered.
STF05/10 drive will stop working when this alarm is triggered.
For STF10 drives, If a regulated power supply is used, and that is near the driver maximum voltage of 75VDC, a voltage clamp
may be required to prevent the voltage over 75VDC which will occurs a overvoltage fault. When using an unregulated power
supply, make sure the no-load voltage of the supply does not exceed the maximum input voltage 75VDC.
For STF05 drives, If a regulated power supply is used, and that is near the driver maximum voltage of 53VDC ,a voltage
clamp may be required to prevent the voltage over 53VDC which will occurs a overvoltage fault. When using an
unregulated power supply, make sure the no-load voltage of the supply does not exceed the maximum input voltage
53VDC.
2.7.2 Current
When STF drives work with different motors, the recommended power supply output current capacity under different
supply voltage is shown in below table. The STF drive power supply current is lower than the the winding currents
because it uses switching amplifiers to convert a high voltage and low current into low voltage and high current. The
more power supply voltage exceeds the motor voltage,the less current will be required from the power supply.
It is important to note that the current draw is significantly different at higher speeds depending on the torque load to the
motor. Estimating how much current is necessary may require a good analysis of the load to the motor.
