Lenze DSD - Manual (Page 346)

11 Drive Dimensioning
11.6 Inverters
346
Lenze · Drive Solution Designer · Manual · DMS 4.2 EN · 12/2013 · TD23
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11.6 Inverters
11.6.1 Dimensioning criteria
Inverters are dimensioned according to the maximum current and the mean value of the output
current. Depending on the operating conditions, individual components can only be subjected to a
lower load, however, others to a higher load.
• For lower field frequencies, individual inverters have a Derating with regard to the maximum
currents provided.
11.6.1.1 Determination of the utilisation values of the inverter
For the calculation of the required utilisation values, the motor current is calculated in DSD. Here,
DSD considers torques of up to 400 % of the rated torque and, in the case of three-phase AC motors/
servo motors, speeds of up to 500 % / 200 % of the rated speed. Outside of these limits, the calcula-
tion of the current may be inaccurate.
• In order to achieve an optimum coordination of motor and inverter with regard to the control
performance, the DSD only proposes inverters which are not too overdimensioned for the re-
spective control type:
• Inverters that do not meet this condition are highlighted in the selection table. An overdimen-
sioning of the inverter which is too great is problematic for field-oriented controls with regard
to the control quality. In the case of the V/f control there are no limit values for this.
• In specific situations also an inverter with a lower rated output current than the rated motor
current can be selected. This is verified via the thermal check in the DSD.
• For the selection table and with the inverter that is selected later on, the following checks are
carried out and shown in the diagram:
• Maximum utilisation
• Thermal utilisation (Ixt)

Note!
The DSD calculates an angle of tilt of the application (a gradient) of 45° with the stand-
still currents resulting from a possible Derating .
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