12-8 Connection System Synchronous Motors MKD
19.05.2004 Version7.0 DOK-MOTOR*-MKD*******-PR07-EN-P
12.5 Connection Cable
Dimensioning of power cable
The specified and calculated cross sectional area of the cables in this
Rexroth Indramat documentation base on RMS current and the
assumption for “rotating motors”. Base for this calculation are the
specified stillstand-constant current in the technical data. They are
specified as peak values.
The relevant electric currents are in association as follows:
2
I
I
)Motor(dN
)Kabel(
=
==
=
I
(cable)
relevant electric current to dimensioning for the cable
I
dN(Motor)
Stillstand-constant current motor (peak values)
Fig. 12-12: RMS – and peak values (“rotating motor”)
Generally is the dimensioning after RMS current at a “rotating motor”
sufficient.
)Motor(dN)Kabel(
II =
==
=
I
(cable)
relevant electric current to dimensioning for the cable
I
dN(Motor)
Stillstand-constant current motor (peak values)
Fig. 12-13: RMS – and peak values (“motor at stillstand”)
In some cases, applications, working over a longer period, require a
continuous torque at standstill when speed = 0 min
1
for the motors
(standard value see Fig. 12.14) is recommended to manage the cable-
dimensioning as specified peak values in the technical datas (“standstill
motor”).
Motor type period
MKD025 10 min
MKD041, 071, 090, 112 15 min
Fig. 12-14: Working over a longer period
Note: The specified, recommended minimum cross sections is to
be checked by the machine/system manufacturer for the
machine/system-secific conditions and, if necessary,
corrected.
“rotating motor”
“motor at standstill”
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