EB-20X Installation & Service Manual |
Motor Data Package
Kollmorgen | kdn.kollmorgen.com | September 2020
37
This gives the maximum ON time for a given operating torque beginning at ambient temperature.
Examination of this equation reveals that as T
OUT
approaches T
c
, t approaches infinity. This is
expected since we can theoretically operate the motor indefinitely at continuous torque without
exceeding its thermal limits. EQ5 with EQ2 define the motor’s operating time limits.
Example #1
An EB-206-C has the torque vs. speed performance characteristics described in the performance
curve labeled EB-206-C PC 26720. The motor is operating intermittently at 4900 rpm with a
torque of 6.6 lb-ft.
FIND:
a) maximum ON time without exceeding ultimate temperature.
b) the required OFF time for an ON time of 4 seconds.
GIVEN: T
OUT
= 6.6 lb-ft
From the performance curve, the continuous torque at 4900 rpm is obtained.
Tc = 4.0 lb-ft
From Specifications CD-26718 for the EB-206-C motor:
TCTP = 22 min.
(a) The maximum ON time is found from EQ5:
T
MAX
= -TCTP 1n 1-
2
T
OUT
T
C
TCTP = 22 min., Tc = 4.0 lb-ft, TOUT = 6.6 lb-ft
T
MAX
= -22 min 1n 1-
2
4.4
6.6
t
MAX
= -22 min. 1n [0.6327]
t
MAX
= -22 min. 1n(-0.4578)
t
MAX
= 10.0 min.
This says that if the motor has an ON time greater than 10 minutes, it exceeds its thermal
limits.
(b) The required OFF time for a given ON time is found from EQ2.
T
OFF
= - TCTP 1n 1-
(1-e
-t
/TCTP) T
OUT
ON
2
-t
ON
T
C
2
t
ON
= 4 seconds
TCTP = 22 min. 60 sec/min = 1320 seconds
t
OUT
= 6.6 lb-ft
T
C
= 4.0 lb-ft
