
7. DETERMINING THE
ALLOWABLE DUTY CYCLE
B–65152E/03
BCATLTLON EOT TFC α
44
7
DETERMINING THE ALLOWABLE DUTY CYCLE
When machining requires the spindle to accelerate and decelerate
frequently, the average output per cycle must not exceed the continuous
rated output.
The allowable duty cycle for a typical AC spindle motor can be obtained
as shown below.
Motor
speed
Motor
output
One cycle time Dt
Acceleraion
Deceleration
cutting
t
1
t
2
t
3
t
4
t
5
P
1
P
2
P
3
P
4
P
1
P
1
, P
4
: Acceleration/deceleration output [kW] = 30 min rated output at
const. output power range 1.2
Note 1) 10 min rated output at const. output power range 1.2 or
15 min rated output at const. output power range 1.2
apply for some models.
Note 2) This is not a guaranteed value but a guideline.
P
2
: Output with no load [kW] (P
2
=0)
P
3:
Cutting output [kW]
Pav +
P
1
2
t
1
) P
2
2
t
2
) P
3
2
t
3
) P
4
2
t
4
Dt
Ǹ
Average output
NOTE
This is not a guaranteed value but a guideline.
NOTE
1 Cutting output P
3
at motor speed N which is lower than base
speed Nb shall be calculated by the following equation.
P
3
=P
C
Nb/N [kW] (P
C
: Actual cutting output)
Duty cycle and
average output