Schneider Electric 58 TRX

Class 8839 58M Enclosed AC Drives

Application Information

171

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 (1–50 hp) or

10,000 AIC (60–200 hp) or

18,000 AIC (250–400 hp)

and

• 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 125–500 hp. By listing the alternate input

currents when using a series line reactor, the

user could benefit in savings reflected in

conductor and disconnect selection, as

required by the National Electric Code.

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 loc al 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%.