Motor Bearing Currents; Control Cables And Terminals; Access To Control Terminals; Control Cable Routing - Danfoss FC 102 Design Manual

Electrical Installation

6.4.6 Motor Bearing Currents

All motors installed with FC 102 90 kW or higher power
frequency converter should have NDE (Non-Drive End)
insulated bearings installed to eliminate circulating bearing
currents. To minimise DE (Drive End) bearing and shaft
currents, proper grounding of the frequency converter,
motor, driven machine, and motor to the driven machine
is required.
Standard Mitigation Strategies
1. Use an insulated bearing.
2. Apply rigorous installation procedures
2a
6 6
2b
2c
2d
2e
2f
3. Lower the IGBT switching frequency.
4. Modify the inverter waveform, 60° AVM vs.
SFAVM.
5. Install a shaft grounding system or use an
isolating coupling.
6. Apply conductive lubrication.
7. Use minimum speed settings if possible.
8. Try to ensure the line voltage is balanced to
ground. This can be difficult for IT, TT, TN-CS or
Grounded leg systems.
9. Use a dU/dt or sinus filter.
108
Design Guide
Ensure the motor and load motor are
aligned.
Strictly follow the EMC Installation
guideline.
Reinforce the PE so the high frequency
impedance is lower in the PE than the
input power leads.
Provide a good high frequency
connection between the motor and the
frequency converter for instance by
screened cable which has a 360°
connection in the motor and the
frequency converter.
Make sure that the impedance from
frequency converter to building ground
is lower that the grounding impedance
of the machine. This can be difficult for
pumps.
Make a direct ground connection
between the motor and load motor.
Danfoss A/S © Rev. 06/2014 All rights reserved.

6.5 Control Cables and Terminals

6.5.1 Access to Control Terminals

All terminals to the control cables are located underneath
the terminal cover on the front of the frequency converter.
Remove the terminal cover by means of a screwdriver (see
Illustration 6.43).
Illustration 6.43 Enclosure Types A1, A2, A3, B3, B4, C3 and C4
Illustration 6.44 Enclosure Types A5, B1, B2, C1 and C2

6.5.2 Control Cable Routing

Tie down all control wires to the designated control cable
routing as shown in the picture. Remember to connect the
shields in a proper way to ensure optimum electrical
immunity.
Fieldbus connection
Connections are made to the relevant options on the
control card. For details see the relevant fieldbus
instruction. The cable must be placed in the provided path
MG11BC02