Baldor MicroFlex, Installation Manual

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3-22 Basic Installation MN1919
3.7.2 Regenerative energy
The regenerative energy to be dissipated, E, is the difference between the initial energy in the
system (before deceleration begins) and the final energy in the system (after deceleration has
finished). If the system is brought to rest then the final energy is zero.
The energy of a rotating object is given by the formula:
E
=
1
2
×
J
× ω
2
where E is energy, J is the moment of inertia, and ω is the angular velocity.
The regenerative energy, which is the difference between the initial energy and the final energy,
is therefore:
E
=

1
2
×
J
×
U
2

−

1
2
×
J
×
V
2

=
1
2
×
J
×
(
U
2
−
V
2
)
= ________________ J (joules)
Calculate E using the values for J, U and V entered in section 3.7.1. If E is less than the drive’s
regeneration capacity, shown in Table 5 on page 3-20, a regeneration resistor will not be required.
If E is greater than the drive’s regeneration capacity, then continue to section 3.7.3 to calculate
the regenerative and average power dissipation.
3.7.3 Regenerative power and average power
The regenerative power, P
r
, is the
rate
at which the braking energy is dissipated. This rate is
defined by the deceleration period, D. The shorter the deceleration period, the greater the
regenerative power.
P
r
=
E
D
=
________________ W (watts)
Although the resistors shown in Table 6 can withstand brief overloads, the average power
dissipation, P
av
, must not exceed the stated power rating. The average power dissipation is
determined by the proportion of the application cycle time spent regenerating. The greater the
proportion of time spent regenerating, the greater the average power dissipation.
P
av
=
P
r
×
D
C
= ________________ W (watts)