bonitron M3645P, Reference Manual

Page: 51 / 56

User’s Manual
51
7.
A
PPENDIX
7.1.
A
PPLICATION
N
OTES
7.1.1.
S
IZING THE
L
INE
R
EGENERATION
U
NIT
The line regeneration unit is sized for the amount of DC bus current, I
DC
,
which
it must carry. To obtain the amount of DC bus current needed during
deceleration; the load and motor inertias, desired change in RPM, and
required stopping time must be known. With these application variables, the
following calculations can be made to size the regen. Use the equation below
to establish the torque required to decelerate or stop a rotating object.
C
ALCULATE
M
OTOR
T
ORQUE
Calculating the motor torque
𝑇 =
𝑊𝐾
2
𝛥𝑁
308 𝑡
𝑜𝑛
Where
T is torque measured in lb·ft .
1.0 lb·ft = 1.355818 Nm
WK
2
is the total inertial load to be decelerated ( lb·ft
2
).
1.0 lb·ft
2
= 0.04214011 kg · m
2
ΔN is the change in rotational speed (rpm).
308 is a constant
t
on
is time required to decelerate the load (s).
C
ALCULATE
M
OTOR
P
OWER
Calculating the power (HP) regenerated:
𝑃 =
𝑇𝑁
𝑚𝑎𝑥
5252
Where
N
max
is the maximum rotational speed (rpm).
The constant 5252 has units of lb·ft/min/radian .
C
ALCULATE
DC B
US
C
URRENT
Calculating the regenerated DC bus current, I
DC
.
𝐼
𝐷𝐶
=
𝑃(746
𝑊
𝐻𝑃
)
√2𝑉
𝐴𝐶
The DC bus current, I
DC
, is approximated for the following AC line voltages:
For 230 V
AC
systems:
𝐼
𝐷𝐶
= (1.2)𝑃
For 380 V
AC
systems:
𝐼
𝐷𝐶
= (1.4)𝑃
For 460 V
AC
systems:
𝐼
𝐷𝐶
= (2.4)𝑃
For 575 V
AC
systems:
𝐼
𝐷𝐶
= (1.0)𝑃
Once I
DC
is known, you will be able to appropriately size the line regen
based upon its current rating.