Class 8839 58M Enclosed AC Drives
Application Information
Collectively, all facility loads and the building electrical distribution network determines the harmonic levels at the user & electric utility interface. Commonly misapplied, the Electrical Power Research Institute (EPRI) recognizes the 'Point of Common Coupling' or PCC as the interface between user and electric utility (energy meter) in the electrical distribution network. This position will also be supported in the forthcoming Application Guide (P519A) being prepared by the Harmonics Working Group of IEEE. Square D Company will typically provide 'drive isolation transformers' or 'line reactors' as the most cost effective method of harmonic abatement.
For specifications that are regulated by utilities to the IEEE 519 guidelines, there are alternate methods of harmonic abatement. Consult product support or customer service for enclosed drives for configurations and pricing.
Input Currents Ratings
(with and without Line Reactor)
Square D publishes input currents based on distribution system impedance at various available fault current ratings. Our literature reflects multiple input current ratings based on available fault currents
•5,000 AIC
10,000 AIC
18,000 AIC
•22,000 AIC and
•65,000 AIC and
•100,000 AIC
More common, line reactors are provided with the majority of AC Drives today. The reasons proliferate from abnormal line conditions, IEEE 519 guidelines, to power quality concerns. Line reactors provide the most cost effective option to minimize harmonic currents reflected back into the distribution system. The use of line reactance ahead of the AC drive will function best to:
1.Reduce line current harmonic injection into the primary source, limiting the input ‘rms’ currents to less than or equal to motor full load amps.
2.Reduce the available feeder short circuit capacity.
3.Meet specified line impedance requirements. 5 KAIC, 10 KAIC, 22 KAIC, and 65 KAIC short circuit current rating up to 100 hp, and 65
KAIC and 100 KAIC short circuit current rating for
Drive Isolation Transformer
Drive Isolation transformers are designed for maximum benefit when applied to an AC drive. In addition to the functional comparison of a line reactor, drive isolation transformers are normally used for one of the following reasons over a standard line reactor:
1.Match system voltage to drive rating.
2.Meet local or plant codes that require isolation.
3.Capable of correcting line voltage unbalance conditions commonly seen with open delta and corner grounded delta distribution systems.
4.Provides continuity of service for nuisance grounding.
5.Reduces drive induced currents in supply feeder ground and limit ground fault currents.
6.Isolate the electrical common mode noise generated in solid state controllers from the distribution system.
The Class 8839 58M Enclosed AC drives have a high fault withstand capability (up to 65,000 A or 100,000 A depending upon configuration). For these reasons, Square D does not suggest the use of a drive isolation transformer for isolation purposes unless the system requires one or more of the six functions listed above.
Speed Range & Regulation
The Class 8839 58M Enclosed AC drives will operate within the range of 0.1 to 60 Hz (configurable up to 500 Hz). Please note, if operating motors above base speed, the motor manufacturer must approve operation for the specified speed range.
Speed regulation is determined by one of several modes of configuration. Most AC drives utilize the volts/hertz mode where speed regulation is determined by the motor slip, typically 3% or less. The Class 8839 58M Enclosed AC drive utilizes sensorless flux vector mode (SLFV) as standard with 1% speed regulation; with optional tachometer can be improved to 0.5%.
09/2003
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