Parker NX Series, Техническое руководство, Страница: 33 / 116

33 - PVD 3663_GB_NX_March 2017.Docx
3.2.6. Time constants of the motor
3.2.6.1. Electric time constant:
ph ph
ph ph
elec
R
L
_
_


With following values given in the motor data sheet
L
ph_ph
inductance of the motor phase to phase [H],
R
ph_ph
resistance of the motor phase to phase at 25°C [Ohm].
Example:
Motor series NX620EAR
L
ph_ph
= 19.2 mH or 19.2.10
-3
H
R
ph_ph
at 25°C = 2.24 Ohm


elec
= 19.2.10
-3
/2.24= 8.6 ms
An overall summary of motor time constants is given a little further.
3.2.6.2. Mechanical time constant:
3
* )
3
* 3 (
* * 5 . 0
*
*
_ _
_
_
_
ph ph ph ph
ph ph
n ph
n ph
mech
Ke Ke
J R
Ke Kt
J R
 

2
_
_
) (
* * 5 . 0
ph ph
ph ph
mech
Ke
J R


With following values obtained from the motor data sheet:
R
ph_ph
resistance of the motor phase to phase at 25°C [Ohm],
J inertia of the rotor [kgm²],
Ke
ph_ph
back emf coefficient phase to phase [V
rms
/
rad/s
].
The coefficient
Ke
ph_ph
in the formula above is given in [V
rms
/rad/s]
To calculate this coefficient from the datasheet, use the following relation:
60
1000 * * 2
] 1000 / [
_
] / / [
_

rpm V
ph ph
s rad V
ph ph
rms
rms
Ke
Ke

Example:
Motor series NX620EAR
R
ph_ph
at 25°C = 2.24 Ohm
J = 98.10
-5
kgm²
Ke
ph_ph
[V
rms
/
1000rpm
] = 95.7 [V
rms
/
1000rpm
]

Ke
ph_ph
[V
rms/rad/s
] = 95.7/(2*

*1000/60) = 0.9139 [V
rms/rad/s
]


mech
=0.5*2.24*98.10
-5
/(0.9139²) = 1.2 ms