KEB COMBIVERT F5 Instructions For Use

6.4 Motor connection
6.4.1 General instructions
• The motor cables must be designed to the maximum continuous current.
• They are valid for 0...100 Hz (up to 300 Hz the cable losses increase by approx. 25
% due to the skin effect).
• The IGBT modules cause high-frequency interferences, the longer the motor cable
length the higher the discharge to the earth potential.
• The consequence is an increase of conducted interferences on the mains side.
• Ifthemotorcablesaretoolong,dampingofthemainsltersisnolongersufcient
and the permissible interference limits are exceeded.
• At the output of the drive converter, pulses of approximately 1.35-fold of the mains
voltage and very short rise times are generated independently of the output frequency.
• This is the case for all drive converters with modern IGBT inverter technology.
• The voltage of the pulses can almost double at the motor connections depending on
the characteristics of the motor cable.
• This can lead to additional load of the motor and the motor cable insulation.
• Modern speed-controlled drives with their fast rising voltage pulses and high switch-
ing frequencies can cause current pulses through the motor bearings which can
gradually damage the bearing raceways.
ATTENTION
Protect motor against voltage peaks !
► The connecting-up instructions of the motor manufacturer are gen-
erally valid.
► Drive converter switch at the output with a high rate of voltage rise.
Voltage peaks that endanger the insulation system at the motor
can occur especially in case of long motor cables (> 15 m). A motor
choke,adv/dtlterorsine-waveltercanbeusedtoprotectthe
motor.
6.4.2 Selection of the motor cable
Correct selection and laying of the motor cable is very important for high motor ratings:
• Smaller load of the motor bearings by bearing currents.
• Improved EMC characteristics.
• Lower symmetrical operating capacities.
• Less losses by transient currents.
• Due to the high currents, shielded motor cables can be connected in parallel be-
tween drive converter and motor.
• All three phases must passing through each line.
• The required cross-section is described in section => Cable cross-sections.
• To keep asymmetry as small as possible, all motor cables should have the same
length.
• The shielding must be placed always with large surface on both sides (mounting
plate and motor housing).
68
ELECTRICAL INSTALLATION

KEB COMBIVERT F5 Specifications

General

Brand	KEB
Model	COMBIVERT F5
Category	DC Drives
Language	English