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# How to select suitable DC power supply for Altivar 71 drive if powered by DC.

Published date: 14 May 2019

Chose the DC supply in function of the value DC voltage that should be used.
It depend also of the power used, the torque need by the application.
DC bus voltage = Mains Voltage x 1.4142
We have to calculate the power feed by DC bus.
So it depends of the setting point of the voltage DC bus supply.
Example:
Drive part number: ATV71HD90N4 (Three-phase supply voltage: 380…480 V )
DC bus voltage = Mains Voltage x 1.4142
So, The DC Voltage range will be 538 to 678V
VDC= 538V (Like 380Vac):
Efficiency Motor = 0.93
Efficiency Drive =0.974

For 90KW motor used on the hoist application which needs transient torque 2 time Nominal torque at full speed.
The used power will be Pn= 90KW so with overtorque during 2s Pmax= 180KW
The power absorbed by motor will 180/efficiency= 180/0.93= 193KW.
So the power absorbed by the drive will be 193/ efficiency of the drive: 193/0.974= 199KW
On the DC bus for 538V:  Pmax=U*I => I= 199000/538= 369.8A.

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