
B-65332EN/01 CONFIGURATIONS AND SELECTION 0.
2.3.2 Example of Selection
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The cooling unit to be used must has the capacity listed under
"Cooling capacity" in the “SPECIFICATION LIST” in Part I. This
value is determined under the condition that root mean square
torque/rated continuous torque = 1. Under ordinary use conditions, the
capacity is usually lower than the listed value. For example, when root
mean square torque/rated continuous torque = 0.7, the heat output is
reduced to 0.7
2
= 0.49 (49%) as compared with that during continuous
operation with the rated continuous torque. For this reason, as the
required capacity of the cooling unit, the value in the specification list
can be reduced to 49%.
An example of calculation is shown below:
Assume the following machine:
- A-axis:
One D370/300is, water cooling, root mean square torque/rated
continuous torque = 0.7
- B-axis:
One D85/400is, water cooling, root mean square torque/rated
continuous torque = 0.8
Because the cooling capacity required for the A-axis is 1,610 W as
listed in "SPECIFICATION LIST," in Part I, the required cooling
capacity under the above condition is:
1,610[W]×0.7
2
=789[W]
Similarly, the cooling capacity required for the A-axis is:
690[W]×0.8
2
=442[W]
Consequently, if the motors on both the A-and B-axes run
simultaneously, the maximum required cooling capacity is:
789[W]+442[W] =1,231[W]
If the motors on both the A-and B-axes do not run simultaneously, the
required cooling capacity is 789 [W].
To determine the required cooling capacity more precisely, it is
advisable to add the duty curves (root mean square torque/rated
continuous torque) for both axes based on the time axis and calculate
the cooling capacity at the point where the sum is the maximum.
NOTE
1 For how to calculate the root mean square torque, see Part II, "CONFIGURATIONS
AND SELECTION."
2 The cooling capacity calculated as above is required when the internal temperature
of the stator rises to a temperature near the maximum operating temperature. For
this reason, if the machine is apt to be easily deformed by temperature rising, it may
be desirable to select a cooling unit with an adequate margin of the required cooling
capacity.
3 Use of strong cooling can increase the rated continuous torque of the motor to some
extent. Carefully use strong cooling so that condensation does not occur on the
motor due to excessive cooling.