Schneider Electric 58 TRX manual Harmonic Mitigation Equipment Requirements, 182

Class 8839 58M Enclosed AC Drives

Specifications

One disconnect shall be common to the drive controller and bypass contactor.

2.Barriered bypass shall consist of compartmentalized, multi-door enclosure construction that provides electrical isolation of the AC Drive controller from the bypass contactor using two OSHA and UL approved disconnects. This configuration shall remove all power to the drive controller compartment when the drive disconnect is in the open position. This configuration shall allow provide maximum user flexibility if servicing a drive while remaining on bypass.

b.A TEST-NORMAL selector switch shall be used with bypass to allow testing of the AC Drive without running the motor. In the “Test” position the isolation contactor shall remain open preventing motor operation while operating the AC drive.

c.The operator shall have full operational control of the bypass starter using a door mounted AFC/OFF/BYPASS selector switch.

d.Auto transfer to bypass function shall be provided in the event of drive fault or failure. This feature shall be enabled or disabled by an internally mounted selector switch. An adjustable timer shall provide control of the delay time between fault and transfer to bypass.

2.16HARMONIC MITIGATION EQUIPMENT REQUIREMENTS

Note to Specifier: There are several solutions for effective harmonic mitigation. The most common approach is the use of a 5% line reactor. When line reactors are properly sized for the drive controller, the additional source impedance can add provide effective levels of harmonic mitigation for voltage distortion and attenuation of incoming voltage transients. The alternate approaches include the use of isolation transformers and harmonic filters. The typical installation of isolation transformers and filters are separately mounted with proper branch circuit protection. Filters require coordination with the AC Drive power circuit and must not be part of the bypass path. An alternate approach is the use of multi- pulse drives, which are typically specified above 100 hp.

a.The AC Drive shall be provided with a 5% rated line reactor mounted inside the enclosure.

b.The AC Drive shall provide provisions and terminations inside the drive enclosure for branch circuit protection of a separately

mounted isolation transformer or harmonic filter. The AC Drive disconnect shall serve as disconnect for the harmonic filters. Branch circuit protection shall be in accordance with the NEC using fused protection. Harmonic filters shall be isolated from bypass path operation if supplied.

2.17 HARMONIC ANALYSIS

Note to Specifier: Guidelines for voltage and current distortion are addressed in IEEE Standard 519-1992 titled “IEEE Recommended Practices and Requirements for Harmonic Control in Electrical Power Systems”, which suggests distortion limits dependent upon the electric power distribution system for industrial and commercial consumers. Collectively, all facility loads and the building electrical distribution network determines the harmonic levels at the user & electric utility interface. 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. The AC Drives manufacturer can provide calculations through computer modeling, specific to the installation, showing total harmonic voltage distortion. Contractor to provide one line diagram drawings to supplier including transformer impedance. The AC Drive manufacturer needs this information.

a.A harmonic distortion analysis shall be performed and priced as a separate line item by the AC Drive manufacturer based upon documentation supplied by the contractor. The documentation shall consist of one-line diagrams, distribution transformer information (kVA, %Z, and X/R ratio) and emergency standby generator performance specifications. The harmonic distortion analysis report shall be part of the approval drawing process, submitted to the engineer for approval.

b.If the calculations determine that harmonic distortion values are higher than the voltage and current values specified, the drive manufacturer shall provide [line reactors, isolation transformers, harmonic suppressors] to meet the intent of IEEE 519-1992 guidelines.

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09/2003