Determining Dynamic Brake Requirements 2-5
Step 3 Peak Braking Power
P
b
= Peak braking power (watts)
1.0 HP = 746 watts
J
T
= Total inertia reflected to the motor shaft (kg-m
2
)
ω
b
= Rated angular rotational speed
ω
o
= Angular rotational speed,
less than rated speed down to zero
N
b
= Rated motor speed (RPM)
t
3
– t
2
= Deceleration time from ω
b
to ω
o
(seconds)
Calculate Peak Braking Power:
Record Peak Braking Power:
Compare the peak braking power (P
b
) to the drive rated regenerative
power (P
rg
). If the peak braking power is greater than the drive rated
regenerative power, the decel time will have to be increased so that the
drive does not enter current limit. Drive rated regenerative power (P
rg
) is
determined by:
P
rg
= Drive rated regenerative power
V = DC bus regulation voltage from Table A.A
R = Minimum brake resistance from Table A.A
Record Rated Regenerative Power:
P
b
=
P
rg
=
P
b
J
T
ω
b
ω
b
ω
o
–()[]
t
3
t
2
–()
----------------------------------------=
Rad
s
---------
2πN
b
60
------------=
Rad
s
---------
P
b
ooooooooo[]ooooooooo[]ooooooooo ooooooooo–()××
ooooooooo ooooooooo–()
-----------------------------------------------------------------------------------------------------------------------------------------------=
P
rg
V
2
R
-----=
P
rg
ooooooooo[]
2
ooooooooo()
----------------------------------=
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