Lenze DSD - Manual (Page 433)

Lenze · Drive Solution Designer · Manual · DMS 4.2 EN · 12/2013 · TD23
433
17 Restrictions of the drive dimensioning
17.11 Maximum permissible motor cable length
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17.11 Maximum permissible motor cable length
The length and type of the shielded motor cable that is used (PE/PVC cable, capacitance per unit
length of the cable) has an impact on the value of the capacitive earth leakage currents to be expect-
ed. These leakage currents have to be additionally provided by the inverter. Therefore there is a
maximum permissible motor cable length which can be found in the Operating Instructions of the
inverters.
• The maximum permissible length also depends on the power of the respective inverter and is
50 m.
• The maximum possible motor cable length can be increased by means of filters in the motor ca-
ble (permissible for inverters only).
• Also the encoder system used can require limitations where the maximum permissible length
is concerned.
17.12 Effects of low switching frequencies on the motor
DSD takes the impact of the switching frequencies on the inverter into consideration.
• DSD checks the effects of low switching frequencies on the motor assuming that the switching
frequency only decreases below 4 kHz for a short time. The effects have to be checked manually.

Note!
Only relevant for motors that are connected to the inverter by means of a long motor ca-
ble (> 50 m).
Motor type Operation on inverters with switching frequencies f
ch
< 8 kHz
MDFQA 100, 112,
132, 160
Effects
• If f
ch
= 4 kHz, the motor only provides approx. 95 % of its rated torque continuously.
• If f
ch
= 2 kHz, the motor only provides approx. 85 % of its rated torque continuously.
• Increased noise emission.
MQA 20, 22, 26 Effects
• If f
ch
= 4 kHz, the motor only provides approx. 95 % of its rated torque continuously.
• If f
ch
= 2 kHz, the motor only provides approx. 85 % of its rated torque continuously.
MCA 20, 22, 26