Mitsubishi Electric MELDAS MDS-R Series, Technical Specification And Instruction Manual

Page: 232 / 285

Appendix 2. Selection
A2 - 6
(2) For unbalance axis
The regenerative energy differs in the upward stop and downward stop for an unbalance axis. A
constant regeneration state results during downward movement if the unbalance torque is the
same as or larger than the friction torque.
Regenerative energy
A regenerative state only occurs when deceleration torque (downward torque) is generated.
E
RU
= 5.24
×
10
-5
•
η
•
T
du •
N
•
t
d
– Ec (J) • • •
(
2-7)
η
: Motor reverse efficiency
T
du
: Upward stop deceleration torque (N
•
m)
N : Motor speed (r/min)
t
d
: Deceleration time (time constant) (ms)
Upward stop
Ec : Unit charging energy (J)
A regenerative state occurs even during constant rate feed when the upward torque Ts during dropping is
generated.
Calculate so that Ts = 0 when Ts is downward.
2
π
•
η
•
T
s
•
L
E
RD
=
∆ S
+ 5.24
×
10
-5
•
η
•
T
dd •
N
•
t
d
– Ec (J) • • •
(
2-8)
η
: Motor reverse efficiency
T
s
: Upward torque during dropping (N
•
m)
L : Constant speed travel (mm)
∆ S : Travel per motor rotation (mm)
T
dd
: Downward stop deceleration torque (N
•
m)
N : Motor speed (r/min)
t
d
: Deceleration time (time constant) (ms)
Downward stop
Ec : Unit charging energy (J)
The regenerative energy per cycle (E
R
) is obtained using expression (2-9) using one reciprocation as one cycle.
E
R
=E
RU+
E
RD
(J)
• • • (
2-9)
(Example)
Using a machine tool vertical axis driven by an HF153 motor, reciprocation is carried out with F30000 at an
acceleration/deceleration time constant of 100ms for a distance of 200mm. Obtain the regenerative energy
per reciprocation operation in this case.
Where: Servo drive unit : MDS-R-V1-80
Travel per motor rotation : 10 mm
Upward stop deceleration torque : 20 N
•
m
Downward stop deceleration torque : 30 N
•
m
Upward torque during downward movement : 3 N
•
m
Using expression (2-7), the upward stop regenerative energy E
RU
is as follows:
E
RU
= 5.24
×
10
-5
×
0.85
×
20
×
3000
×
100 – 46 = 221.2 (J)
The acceleration/deceleration distance required to accelerate at the 100ms acceleration/deceleration time
constant to 30000mm/min. is as follows:
30000 × 100
2
×
60
×
1000
= 25 (mm)
Therefore, the constant speed travel is 150mm.
The downward stop regenerative energy E
RD
is obtained using the following expression (2-8).
2 π× 0.85 × 3 × 150
E
RD
=
10
+ 5.24 × 10
-5
× 0.85 × 30 × 3000 × 100 – 46 = 595.2 (J)
Thus, the regenerative energy per reciprocation operation E
R
is as follows:
E
R
= 221.2 + 595.2 = 816.4 (J)