Mitsubishi Electric MELDAS MDS-R-V1-40 - Page 232

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.
ERU = 5.24×10
-5
•
η • Tdu • N • td – Ec (J)
• • • (2-7)
η
: Motor reverse efficiency
Tdu : Upward stop deceleration torque (N•m)
N : Motor speed (r/min)
td : 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.
2π • η • Ts • L
ERD =
∆S
+ 5.24 × 10
-5
•
η • Tdd • N • td – Ec (J)
• • • (2-8)
η
: Motor reverse efficiency
Ts : Upward torque during dropping (N•m)
L : Constant speed travel (mm)
∆S : Travel per motor rotation (mm)
Tdd : Downward stop deceleration torque (N•m)
N : Motor speed (r/min)
td : Deceleration time (time constant) (ms)
Downward stop
Ec : Unit charging energy (J)
The regenerative energy per cycle (ER) is obtained using expression (2-9) using one reciprocation as one cycle.
ER=ERU+ERD (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 ERD is obtained using the following expression (2-8).
2π×0.85×3×150
ERD =
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)