Parker EY Series - Page 31

31 – Pvd3675_Gb_Ey_Septembre_2017
Remarks :
For a DC motor, the mechanical time constant σ
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 σ
elec
is much smaller
than the mechanical time constant σ
mech
(for the motor EY630EAK taken as illustration,
it is not the case because we obtain σ
mech<
σ
elec
.).
An overall summary of motor time constants is given a little further.
3.2.6.3. Constante de temps thermique du cuivre :
cuivretherm
CthRth *= τ
]
/[
]
[
]/[
389*
KkgJ
Kg
cuivre
KJ
cuivre
MasseCth
°
°
=
With:
Rth thermal resistance between copper and ambient temperature [°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]
EY310
3.0
1.1
56
EY420
4.6
1.4
72
EY430
5.2
1.1
76
EY620
8.6
1.3
137
EY630
10.3
1.0
158
EY820
8.5
2.1
135
EY840
11.0
1.5
171
EY860
12.9
1.3
206