Rockwell Automation 1336_F_E_T_S SERIES A CHOPPER BRAKE MODULE User Manual
Page 8
Heavy Duty Dynamic Braking
8
1336-5.65 — March, 2007
Step 1 — Determine Gear Ratio
Step 2 — Determine the Total Inertia
Step 3 — Calculate the Peak Braking Power
Compare the peak braking power to that of the rated motor power. If the
peak braking power is greater that 1.5 times that of the motor, then the
deceleration time (t
3
- t
2
) needs to be increased so that the drive does not
go into current limit.
GR = _________
GR=
Turns of Load
Turns of Motor
J
T
= J
m
+ GR
2
✕
J
L
J
T
= Total inertia reflected to the motor shaft (kg-m
2
or lb-ft
2
)
J
m
= Motor inertia (kg-m
2
or lb-ft
2
)
GR = Gear ratio of any gear between motor and load
(dimensionless)
J
L
= Load inertia (kg-m
2
or lb-ft
2
)
1.0 lb-ft
2
= 0.04214011 kg-m
2
J
T
= [
+
]
✕
[
]
J
T
= __________ kg-m
2
or lb-ft
2
P
b
=
J
T
= Total inertia reflected to the motor shaft (kg-m
2
)
ω
b
= Rated angular rotational speed (Rad / s = 2
πN
b
/ 60)
ω
o
= Angular rotational speed,
less than rated speed down to zero (Rad / s)
N
b
= Rated motor speed (RPM)
t
3
- t
2
= Deceleration time from
ω
b
to
ω
o
(seconds)
P
b
= Peak braking power (watts)
1.0 HP = 746 watts
J
T
✕
ω
b
(
ω
b
-
ω
o
)
(t
3
- t
2
)
P
b
=
[
✕
(
-
)]
[
–
]
P
b
= __________watts