10.1 Selecting Motors and Inverters
10-13
Chapter 10 SELECTING OPTIMAL MOTOR AND INVERTER CAPACITIES
Before proceeding this calculation, obtain the motor shaft moment of inertia J
1
, the load shaft moment of
inertia converted to motor shaft J
2
, maximum load torque converted to motor shaft τ
L
, and the
reduction-gear efficiency η
G
. Apply the maximum motor output torque τ
M
according to an actual speed
thread ΔN as follows.
[τ
M
in N ≤ N
O
] Constant output torque range
60 • P
O
τ
M
=
2π • N
O
(N • m) (10.18)
[τ
M
in N
O
≤ N ≤ N
1
] Constant output power range (The motor output torque is inversely proportional to
the motor speed)
60 • P
O
τ
M
=
2π • N
(N • m) (10.19)
If the result obtained by the above calculation does not satisfy the target value, select an inverter with one
rank higher capacity.
[5] Calculating non-linear deceleration time
Use the following expression to obtain the non-linear deceleration time as well as for the acceleration time
shown in [4].
J
1
+ J
2
/ η
G
2π • U N
Ut
DEC
=
τ
M
- τ
L
• η
G
•
60
(s) (10.20)
In this expression, both τ
M
, and ΔN are generally negative values so that the load torque τ
L
serves to
assist the deceleration operation. For a lift load, however, the load torque τ
L
is a negative value in some
modes. In this case, the τ
M
, and τ
L
will take polarity opposite to each other and the τ
L
will serve to
prevent the deceleration operation of the lift.
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