6
Operating modes and limit values
Safe operation of category 2 motors on inverters
Operating Instructions – EDR..71 – 315, EDRN63 – 315
97
6.4
Safe operation of category 2 motors on inverters
Project planning is the basic requirement for safe operation of explosion-proof motors.
The following points have to be considered:
•
Check the conditions of the typical application.
•
With deviations from the typical application: Calculate the motor terminal voltage.
•
Adhere to the thermal torque limit characteristic curve.
•
Adhere to the dynamic limit torque.
•
Adhere to the motor limit frequency.
•
Select a suitable frequency inverter.
•
Use a braking resistor if regenerative operation cannot be ruled out.
•
Check the overhung and axial loads on the motor shaft of stand-alone motors.
•
Observe the maximum gear unit input speed, see n
emax
on the nameplate.
•
Observe the maximum gear unit output torque, see M
amax
on the nameplate.
6.4.1
Motor terminal voltage
The calculation of the motor terminal voltage is an important component of project
planning.
If the conditions differ from the typical application, you have to calculate the start of
field weakening f
D*
and the torque M
E*
, see chapter "Special application" (→
6.4.2
Maximum permitted torques
The thermal torque limit characteristic curve shows the permitted maximum torque for
continuous operation of the motor.
If the effective operating point is below the thermal limit characteristic curve, the val-
ues may be exceeded briefly, see the chapter "Typical application" (→
The permitted maximum dynamic limit torque is determined by the short-term current
limitation (150% I
N motor
).
For the value I
N Motor
, refer to the EU type examination certificate or the nameplate.
6.4.3
Maximum and minimum permitted frequencies
The maximum and minimum frequencies are indicated on the nameplate. The actual
values may not exceed or fall below these specifications.
25896334/EN – 06/2019