Ground Leakage Current; Acoustic Noise; Balance; Extreme Running Conditions - Danfoss FCM305 56 Instruction Manual

Ground Leakage Current

Ground leakage current is primarily caused by the
capacitance between motor phases and the motor
frame. The RFI filter contributes additional leakage
current, as the filter circuit is connected to ground
through capacitors.
The amount of the leakage current to the ground
depends on the following factors, in order of priority:
1. Switching frequency
2. Motor grounded on site or not
The leakage current is of importance to safety
during handling/operation of the adjustable
frequency drive if (by mistake) the adjustable
frequency drive has not been grounded.
NOTE!
Since the leakage current is > 3.5 mA (approx. 4-20
mA), reinforced grounding must be established (see
Quick Guide MG.03.A1.02), which is required if EN
50178 is to be complied with. Never use ELCB
relays that are not suitable for DC fault currents
(type A).
If ELCB relays are used, they must be:
- Suitable for protecting equipment with a direct
current content (DC) in the fault current (3-
phase bridge rectifier)
- Suitable for power-up with short charging
current to ground
- Suitable for a high leakage current.

Acoustic Noise

Below are the typical values measured at a distance
of 3 ft (im). from the unit at full load:
2 pole
FCM 305
FCM 311
FCM 315
FCM 322
FCM 330
FCM 340 62 dB(A)
FCM 355 64 dB(A)
FCM 375
17-4
FCM 300 Series

Balance

The FCM 300 is balanced to class R according to
ISO2373 (reduced balance). For critical applications
especially at high speed (>4000 RPM) special ba-
lance (class S) might be required.

Extreme Running Conditions

Motor-generated overvoltage
The voltage in the intermediate circuit is increased
when the motor acts as a generator. This occurs in
two cases:
1. The load drives the motor (at constant output
2. During deceleration ("ramp-down") if the
The control unit attempts to correct the ramp if
possible.
The inverter turns off to protect the transistors and
the intermediate circuit capacitors when a certain
voltage level is reached.
AC Line drop-out
During an AC Line drop-out, FCM 300 Series
continues until the intermediate circuit voltage drops
below the minimum stop level, which is typically
15% below FCM 300 Series's lowest rated supply
voltage.
The time before the inverter stops depends on the
mains voltage before the drop-out and on the motor
load.
Static overload
4 pole
When FCM 300 Series is overloaded (the current
54 dB(A)
limit in parameter 221 has been reached), the
58 dB(A)
controls will reduce the output frequency in an
59 dB(A)
attempt to reduce the load.
58 dB(A)
61 dB(A)
If the overload is excessive, a current may occur
63 dB(A)
that makes the FCM 300 cut out after approx. 1.5
60 dB(A)
sec.
61 dB(A)
frequency from the adjustable frequency drive),
i.e. the load generates energy.
moment of inertia is high, the load is low and
the ramp-down time is too short for the energy
to be dissipated as a loss in the VLT adjustable
frequency drive, the motor and the installation.
MG.03.B6.2G - VLT is a registered Danfoss trademark