5  Operation
5.2.7  SEMI F47 Function (Torque Limit Function for Low Power Supply Voltage for Main Circuit)
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5.2.7 SEMI F47 Function (Torque Limit Function for Low Power Supply Voltage for 
Main Circuit)
The torque limit function detects a low voltage and limits the output current if the power supply voltage for the 
main circuit drops to a specified value or below.
This function complies with SEMI F47 standards for semiconductor production equipment. 
Combining this function with the parameter for Instantaneous Power Cut Hold Time allows the servomotor to 
continue operating without stopping for an alarm or without recovery work even if the power supply voltage 
drops.
•  The function is able to cope with instantaneous power interruptions in the voltage and 
time ranges stipulated in SEMI F47. An uninterruptible power supply (UPS) is 
required as a backup for instantaneous power interruptions that exceed these voltage 
and time ranges.
•  The function is intended for voltage drops in the main circuit power supply. The follow-
ing restrictions apply when it is used to provide an instantaneous power cut hold time 
in the control power supply. (There are no restrictions for the 200 V SERVOPACKs.)
<Control Power Supply Restrictions>
400 V SERVOPACKs: Provide the control power supply from a 24 VDC power supply 
   that complies with SEMI F47 standards.
100 V SERVOPACKs: Provide the control power supply from an uninterruptible power 
   supply (UPS).
•  Set the host controller and SERVOPACK torque limit so that a torque reference that 
exceeds the specified acceleration will not be output when the power supply for the 
main circuit is restored.
•  Do not limit the torque to values lower than the holding torque for the vertical axis.
•  This function controls torque within the range of the SERVOPACK's capability when 
the power is cut. It is not intended for use under all load and operating conditions. Use 
the actual device to set parameters while confirming correct operation.
•  Setting the Instantaneous Power Cut Hold Time lengthens the amount of time from 
when the power supply is turned OFF until the motor current turns OFF. Use the input/
output of the servo ON signal to stop the motor current.