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8-4
Determination of Appropriate Power Supply Units
DC bus continuous power for
main and servo drives
8.3
DC Bus Peak Power
If main and servo drives are operated on a power supply unit, the required
DC bus continuous power needs to be added.
It is the spindle drive in a NC machine tool that primarily determines the
DC bus power needed. Therefore, the following equation should be
applied in such applications:
=
P
P [
ZW
mHa
0,3:
experimental value for standard machine tools
1,25:
constant for motor and controller efficiency
P
:
DC bus continuous power [kW]
ZW
P
... P
:
continuous mech. servo drive output [kW]
mSe1
mSen
P
:
nominal power for spindle drives (shaft output) [kW]
ZWHa
Fig. 8-11:
DC bus continuous power for spindle and servo drives in machine
tools
The DC bus peak power is demanded of the power supply unit when, e.g.,
several axes of a machine tool simultaneously accelerate to rapid
traverse and then go to a workpiece after a tool change.
Damages due to overloaded power supply unit!
⇒ Damages to the power supply unit can be avoided, if
the sum of the peak power of all drives does not
exceed the DC bus peak power of the power supply
CAUTION
unit.
P
ZWS
1,25:
constant for motor and controller efficiency
M
:
acceleration torque in NC mode [Nm]
NC
M
:
weight torque in vertical axes [Nm]
G
n
:
speed in rapid traverse [min
eil
P
:
DC bus peak power [kW]
ZWS
Fig. 8-12:
DC bus peak power per drive
P
:
DC bus peak power [kW]
ZWS
P
: DC bus peak power of the power supply unit [kW]
ZWS03
Fig. 8-13:
Sum of DC bus peak powers
+
+
+
0
3 ,
*
P (
P
...
mSe
1
mSe
2
±
(
M
M
* )
n
*
, 1
=
NC
G
eil
9550
-1
]
∑
≤
P
P
ZWS
ZWS
03
DOK-INDRV*-HMV-*******-PR01-EN-P
Rexroth IndraDrive
P
)]
*
, 1
25
mSen
25
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