Mitsubishi Electric MELDAS MDS-R Series - Page 276

Appendix 2. Selection
A2 - 7
(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

  Tdu  N  td – Ec (J)

  (2-7)

: 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.
2    Ts  L
ERD =
∆S
+ 5.24
 10
-5

  Tdd  N  td – Ec (J)
   (2-8)

: 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
er reciprocation operation in this case. p
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
onstant to 30000mm/min. is as follows: c
30000100
2
601000
= 25 (mm)
Therefore, the constant speed travel is 150mm.
T he downward stop regenerative energy E
RD is obtained using the following expression (2-8).
2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)
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