•
Do not ground one frequency converter to
another in a “daisy chain” fashion
•
Keep the ground wire connections as short as
possible
•
Using high-strand wire to reduce electrical noise
is recommended
•
Follow motor manufacturer wiring requirements
2.4.2.1 Leakage Current (>3.5 mA)
Follow national and local codes regarding protective
earthing
of equipment with
a leakage current > 3.5 mA.
Frequency converter technology implies high frequency
switching at high power. This will generate a leakage
current in the earth connection. A fault current in the
frequency converter at the output power terminals might
contain a DC component which can charge the filter
capacitors and cause a transient earth current. The earth
leakage current depends on various system configurations
including RFI filtering, screened motor cables, and
frequency converter power.
EN/IEC61800-5-1 (Power Drive System Product Standard)
requires special care if the leakage current exceeds 3.5 mA.
Earth grounding must be reinforced in one of the
following ways:
•
Earth ground wire of at least 10 mm
2
•
Two separate earth ground wires both complying
with the dimensioning rules
See EN 60364-5-54 § 543.7 for further information.
Using RCDs
Where residual current devices (RCDs), also known as earth
leakage circuit breakers (ELCBs), are used, comply with the
following:
Use RCDs of type B only which are capable of
detecting AC and DC currents
Use RCDs with an inrush delay to prevent faults
due to transient earth currents
Dimension RCDs according to the system configu-
ration and environmental considerations
2.4.2.2 Grounding Using Shielded Cable
Earthing (grounding) clamps are provided for motor wiring
(see
Illustration 2.7).
Illustration 2.7 Grounding with Shielded Cable
2.4.3 Motor Connection
WARNING
INDUCED VOLTAGE!
Run output motor cables
from multiple frequency
converters separately. Induced voltage from output motor
cables run together can charge equipment capacitors even
with the equipment turned off and locked out. Failure to
run output motor cables separately could result in death
or serious injury.
•
For maximum wire sizes
see 10.1 Power-dependent
Specifications
•
Comply with local and national electrical codes
for cable sizes
•
Motor wiring knockouts or access panels are
provided at the base of IP21 and higher
(NEMA1/12) units
•
Do not install power factor correction capacitors
between the frequency converter and the motor
•
Do not wire a starting or pole-changing device
between the frequency converter and the motor
•
Connect the 3-phase motor wiring to terminals
96 (U), 97 (V), and 98 (W)
•
Ground the cable in accordance with grounding
instructions provided
•
Torque terminals in accordance with the
information provided in 10.4 Connection
Tightening Torques
Installation
VLT
®
HVAC Drive Operating Instructions
MG11AI02 - VLT
®
is a registered Danfoss trademark
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