2-25
TI71M01D06-01EN 3rd Edition: 2012.12.01
(3) How to calculate regeneration energy
Acceleration at motor deceleration
The acceleration at deceleration is expressed as follows:
(
)
2
max
rad/s
2
＝
dec
r
t
N
π
ω
Torque and output at motor deceleration
The torque at motor deceleration is expressed as a function of inertia and acceleration as
follows:
(
)
(
)
2
rad/s
*
＝
ω
M
L
M
J
J
T
+
The output in this case is as follows:
( )
Ｗ
＝
ω
×
Mdec
OM
T
P
Motor current at torque T
M
The motor current is obtained from the current - torque characteristic curve and set to 80% of
this value in order to take fluctuations of the maximum motor torque into consideration.
Moreover, since this value is the peak value, it must be converted to the actual value.
The peak current value is obtained from the following formula:
( )
A
8
.
0
P
＝
×
TI
M
K
T
I
The actual current value is obtained from the following formula:
(
)
Arms
8
.
0
2
M
＝
×
×
TI
M
K
T
I
Motor loss power (copper loss)
( )
Ｗ
＝
2
2
3
M
B
A
ML
I
R
P
×
×
−
Power AMP loss power
The power AMP power consumption is obtained from the following formula based on the
current - AMP loss constant and peak current:
( )
Ｗ
＝
M
I
K
P
PL
PL
×
Time t
c
The time it takes for motor output current to become smaller than the total loss power, t
c
, is
obtained as follows.
The total loss power is obtained from the following formula:
( )
Ｗ
＝
PL
ML
TL
P
P
P
+
The time until t
c
is then obtained from the following formula:
( )
ｓ
−
＝
×
OM
TL
c
P
P
t
t
1
Energy returned to smoothing capacitor
The energy corresponding to the shaded area shown in (2) is obtained as follows.
(
) ( )
Ｊ
−
＝
2
TL
OM
c
RC
P
P
t
E
×