NORD Drivesystems B1091-1 - Manual (Page 8)

Motors in fi operation for Category 3D – Planning guideline for B 1091
8 B 1091-1 GB-3213
1. Technical explanations
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1.1 General
The Category 3D motors supplied by NORD DRIVESYSTEMS comply with standard EN 50281-1-1
(electrical equipment for use in areas with inflammable dust) and EN 50014 (Electrical equipment for
explosion hazard areas). Category 3D motors with efficiency class IE2 comply with the standards
EN 60079-0 and EN 60079-31. In both versions the insulation of the windings is generally designed for
operation with frequency inverters. For operation with frequency inverters, the motors are always
equipped with triple thermistors as per DIN 44082.
For variable speed drives, the thermistor is the most important protective element for compliance with
the maximum surface temperature, which is stated in the type plate of the motor.
As the thermistor only provides an indirect temperature monitoring of some components of the
motor, e.g. the motor shaft, it is necessary to observe all the specifications stated in this
planning guideline.
The operating ranges stated in the Appendix have been checked in the course of extensive test runs
and only these ranges are approved. Compliance with the listed procedures is therefore a prerequisite
for the planning and commissioning of Device Group II regulated drive units in Zone 22 (non-
conducting dust).
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1.2 Overview
Necessary frequency inverter characteristics:
• Only frequency inverters with a vector regulation process which provides load-dependent terminal
voltage adjustment in the low speed range may be used.
• The maximum output voltage of the frequency inverter must not be less than 91% of the mains
voltage.
• The inverter must provide i²*t monitoring which is adjustable to the rated current for the motor.
• The pulse frequency of the output stage must be adjustable to 4 kHz or higher.
• If the inverter does not have an input for evaluation of the thermistor, the evaluation must be
carried out by a separate triggering device, which switches off the inverter. Operation without
evaluation of the thermistor is not permitted.
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