Parker EX Series - Time Constants of the Motor

65 – Pvd3665_Gb_Ex_August 2022
3.2.8. Time constants of the motor
3.2.8.1. Electric time constant:
phph
phph
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 EX620EAO
L
ph_ph
= 14 mH or 14.10
-3
H
R
ph_ph
at 25°C = 1.63 Ohm
→ 
elec
= 14.10
-3
/1.63 = 8.6 ms
An overall summary of motor time constants is given a little further.
3.2.8.2. Mechanical time constant:
3
*)
3
*3(
**5.0
*
*
__
_
_
_
phphphph
phph
nph
nph
mech
KeKe
JR
KeKt
JR
== 
2
_
_
)(
**5.0
phph
phph
mech
Ke
JR
= 
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/[
_
]//[
_

rpmV
phph
sradV
phph
rms
rms
Ke
Ke =
Example:
Motor series EX620EAO
R
ph_ph
at 25°C = 1.63 Ohm
J = 98.10
-5
kgm²
Ke
ph_ph
[V
rms
/
1000rpm
] = 81.7 [V
rms
/
1000rpm
]
→ Ke
ph_ph
[V
rms/rad/s
] = 81.7/(2**1000/60) = 0.7802 [V
rms/rad/s
]
→ 
mech
=0.5*1.63*98.10
-5
/(0.7802²) = 1.3 ms