Parker NX Series, Technical Manual

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34 - PVD 3663_GB_NX_March 2017.Docx
Remarks:
For a DC motor, the mechanical time constant

mech
represents the duration needed
to reach 63% of the final speed when applying a voltage step without any resistant
torque. However this value makes sense only if the electric time constant

elec
is much
smaller than the mechanical time constant

mech
(for the motor NX620EAR taken as
illustration, it is not the case because we obtain

mech<

elec
.).
An overall summary of motor time constants is given a little further.
3.2.6.3. Thermal time constant of the copper:
copper iron copper therm
Cth Rth *
_


] / [
] [ ] / [
389 *
K kg J
Kg
copper
K J
copper
Mass Cth



With:
Rth
copper_iron
thermal resistance between copper and iron [°K/W]
Cth
copper
thermal capacity of the copper [J/°K]
Mass
copper
mass of the copper (winding) [kg]
Hereunder is given an overall summary of motor time constants:
Type
Electric time
constant [ms]
Mechanical time
constant [ms]
Thermal time constant
of copper [s]
NX110E
1.2 1.8 26.1
NX205E
2.6 2.2 38.5
NX210E
2.0 1.5 42.7
NX310E
3.0 1.1 60.2
NX420E
4.6 1.4 71.0
NX430E
5.2 1.1 79.8
NX620E
8.6 1.3 137
NX630E
10.3 1.0 158
NX820E
8.5 2.1 135
NX840E
11.0 1.5 171
NX860E
12.9 1.3 206
NX860V
12.9 1.3 81