Ground Leakage Current; Selection Of Brake Resistor - Danfoss FC 300 Design Manual

3. Introduction to FC 300
The functional galvanic isolation (a and b in drawing) is for the 24 V backup option and for the
RS-485 standard bus interface.
3

3.6.1. Ground Leakage Current

3.7.1. Selection of Brake Resistor

To handle higher demands by generatoric braking, a brake resistor is necessary. Using a brake
resistor ensures that the energy is absorbed in the brake resistor and not in the adjustable fre-
quency drive.
If the amount of kinetic energy transferred to the resistor in each braking period is not known,
the average power can be calculated on the basis of the cycle time and braking time, also called
intermitted duty cycle. The resistor intermittent duty cycle is an indication of the duty cycle at
which the resistor is active. The figure below shows a typical braking cycle.
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At altitudes higher than 6,600 feet [2 km], please contact Danfoss Drives regarding
PELV.
Warning:
Touching the electrical parts may be fatal - even after the equipment has been dis-
connected from line power.
Also make sure that other voltage inputs have been disconnected, such as load
sharing (linkage of DC intermediate circuit), as well as the motor connection for
kinetic backup.
Using VLT AutomationDrive FC 300: wait at least the amount of time indicated in
the Safety Precautions section.
A shorter time is allowed only if indicated on the nameplate for the specific unit.
Leakage Current
The ground leakage current from the FC 300 exceeds 3.5 mA. To ensure that the
ground cable has a good mechanical connection to the ground connection (terminal
95), the cable cross-section must be at least 0.016 in.
ground wires terminated separately.
Residual Current Device
This product can cause DC current in the protective conductor. Where a residual
current device (RCD) is used for extra protection, only an RCD of Type B (time de-
layed) shall be used on the supply side of this product. See also RCD Application
Note MN.90.GX.02.
Protective grounding of the adjustable frequency drive and the use of RCDs must
always follow national and local regulations.
NOTE
Motor suppliers often use S5 when stating the permissible load, which is an expres-
sion of intermittent duty cycle.
MG.33.B9.22 - VLT
2 [10 mm
® is a registered Danfoss trademark.
FC 300 Design Guide
2 ] or have 2 rated