Acoustic Noise; Peak Voltage On Motor - Danfoss FC 300 Design Manual

FC 300 Design Guide

Acoustic Noise

"
The acoustic noise from the adjustable frequency drive comes from three sources:
1. DC intermediate circuit coils.
Integral fan.
2.
RFI filter choke.
3.
The typical values measured at a distance of 3.3 ft (1 m) from the unit:
FC 301/ FC 302
PK25-P7K5: 200-240 V, 380-500 V, 525-600V
Reduced fan speed
Full fan speed

Peak Voltage on Motor

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When a transistor in the inverter bridge switches, the voltage across the motor in-
creases by a dV/dt ratio depending on:
the motor cable (type, cross-section, length shielded or non-shielded)
-
inductance
-
The natural induction causes an overshot U
depending on the voltage in the intermediate circuit. The rise time and the peak voltage U
service life of the motor. If the peak voltage is too high, especially motors without phase coil insulation are
affected. If the motor cable is short (a few meters), the rise time and peak voltage are lower.
If the motor cable is long (328 ft / 100 m), the rise time and peak voltage increase.
If very small motors are used without phase coil insulation, connect an LC fil-
ter to the adjustable frequency drive.
FC 300 Selection
in the motor voltage before it stabilizes itself at a level
PEAK
MG.33.B6.22 - VLT is a registered Danfoss trademark
IP20/IP21/IP4Xtop/Type 1 (NEMA 1)
51 dB(A)
60 dB(A)
affect the
PEAK
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