Chapter 1. Description of Hybrid Servo Drives | VFD-VJ  
 
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3.  Rated Torque and Rated Power of the Motor 
When holding pressure is under maximum pressure, the required torque cannot exceed 
1.5 times of the motor’s rated torque (depending on the data provided by the motor’s 
manufacturer) at most or the motor would be overheated. Let us take the factor 1.5 as an 
example, if the rated torque of the motor is 77 N-m, the motor with a power of 12kW* and 
a rated speed of 1500 rpm can be chosen. 
*The power of the motor is calculated by using 
)60/2()()(
 rpmmNTWP  
4.  Maximum Current of the Motor 
Example: Check the parameter kt (Torque/A) in the motor’s specifications fist. If kt = 3.37, 
the maximum current is approximately 116/3.37 = 34A at the maximum torque 
of 116 N-m. 
5.  Selection of Matched Hybrid Servo Drive 
Example: Look up the heavy-duty capability for each hybrid servo drive in the product 
specifications. 
If the holding pressure is under the maximum pressure of 17.5 Mpa by using 
with a pump of 32cc/rev, the required motor current would be approximately 
1883A. 
Under such a current value, overload may occur in different times due to 
different models. 
For model VFD450VL43C-JO, the overload may occur within 20 sec.. 
For model VFD550VL43C-JO, the overload may occur approximately after 60 
sec.. 
NOTE
 
  If there is no suitable motor that meets the specifications, a motor with a higher rated power 
can be used instead.   
  For any information about the hybrid servo drives or any assistance in detailed configuration 
of your company's products, please contact the manufacturer.   
  Before running the hybrid servo drive, verify if there’s enough cooling oil in the oil circulation. 
You need to preheat the cooling medium such as cooling oil to prevent any condensation caused 
by temperature differences. 
 
  Make sure that the cooling medium stay liquidized to keep the heat dissipating system stays 
functional. So do follow the oil temperature limitation (10 ~ 50 ºC), (50 ºF ~ 122 ºF) to prevent 
overheating on cooling oil. 
 
  Heat dissipating system:    The maximum working pressure cannot go over 1.5 bar at the oil 
inlet. Do not exchange the positions of oil inlet and oil outlet. Verify the specification of 
connector’s pope thread (1/2” PT) to prevent damaging the pipe thread. Wrap pipe threads with 
teflon tape (thread seal tape). 
 
    Use wall-mounting method and follow the space requirements during the installation         
of the hybrid servo system