Table of Contents
Advertisement
3.2.8. Time constants of the motor
3.2.8.1.
L
ph
_
ph
elec
R
ph
_
ph
With following values given in the motor data sheet
L
inductance of the motor phase to phase [H],
ph_ph
R
resistance of the motor phase to phase at 25°C [Ohm].
ph_ph
Example:
Motor series NK620EAR
L
= 19.2 mH or 19.2.10
ph_ph
R
at 25°C = 2.24 Ohm
ph_ph
-3
= 19.2.10
/2.24=8.6 ms
elec
An overall summary of motor time constants is given a little further.
3.2.8.2.
Mechanical time constant:
R
*
J
ph
_
n
mech
Kt
*
Ke
ph
_
n
3 (
0
5 .
*
R
*
ph
_
ph
mech
2
(
Ke
)
ph
_
ph
With following values obtained from the motor data sheet:
R
resistance of the motor phase to phase at 25°C [Ohm],
ph_ph
J
inertia of the rotor [kgm²],
Ke
back emf coefficient phase to phase [V
ph_ph
The coefficient Ke
ph_ph
To calculate this coefficient from the datasheet, use the following relation:
Ke
ph
Ke
ph
_
ph
[
V
/
rad
/
s
]
rms
Example:
Motor series NK620EAR
R
at 25°C = 2.24 Ohm
ph_ph
-5
J = 98.10
kgm²
Ke
[V
/
] = 95.7 [V
ph_ph
rms
1000rpm
Ke
[V
] = 95.7/(2**1000/60) = 0.9139 [V
ph_ph
rms/rad/s
=0.5*2.24*98.10
mech
Electric time constant:
-3
H
0
5 .
*
R
*
J
ph
_
ph
Ke
Ke
ph
_
ph
ph
_
ph
*
* )
3
3
J
in the formula above is given in [V
_
ph
[
V
/
1000
rpm
]
rms
2
*
*
1000
60
/
]
rms
1000rpm
-5
/(0.9139²) = 1.2 ms
34 - PVD 3664_GB_NK-November 2016.Docx
/
].
rms
rad/s
/rad/s]
rms
]
rms/rad/s
Advertisement
Table of Contents
