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INPUT LINE REQUIREMENTS

4 - CONNECTIONS

4.2 Input Line Requirements

4.2.1 Line Voltage

See the Power and Current Ratings tables on page 10 for the allowable uctuation of AC line voltage for

your particular RSi S4 model. A supply voltage above or below the limits given in the table will cause the

drive to trip with either an overvoltage or undervoltage fault.

Exercise caution when applying the RSi S4 AC drive on low-line conditions.

For example, an RSi S4 Series VFD will operate properly on a 208VAC line - but the maximum output

voltage will be limited to 208VAC. Now if a motor rated for 230VAC line voltage is controlled by this

drive, higher motor currents and increased heating will result.

Therefore, ensure that the voltage rating of the motor matches the applied line voltage. If other than 60Hz

output is desired, proper V/Hz can be programmed into the RSi S4 drive by setting FUN 01 (Nom Mtr

Volt) and AFN 01 (Nom Mtr Freq) parameters.

4.2.2 Line Capacity

If the source of AC power to the RSi S4 drive is greater than 10 times the transformer kVA rating listed in

the table below, an isolation transformer or line reactor is recommended. Consult the factory for assistance

in sizing the reactor.

Recommended Isolation Transformer Sizing for RSi S4 Sensorless Drive

z NOTE: RSi S4 Drives are suitable for use on a circuit capable of delivering not more than 65,000 rms

symmetrical Amperes at maximum rated Voltage.

4.2.3 Use of Isolation Transformers and Line Reactors

In nearly all cases, the RSi S4 drive may be connected directly to a power source. However, in the

following cases, a properly-sized isolation transformer or line reactor should be utilized to minimize the

risk of drive malfunction or damage:

When the line capacity exceeds the ratings of the drive (• see Section 4.2.2).

When power factor correction capacitors are used on the drive’s power source. •

When the power source experiences transient power interruptions or voltage spikes. •

When the power source supplying the drive also supplies large devices (such as DC drives) that contain •

controlled rectiers.

When the drive is powered from an ungrounded (oating) Delta connected source. In this case a drive •

isolation transformer utilizing a grounded secondary should be used.

4.2.4 Phase Imbalance

Phase voltage imbalance of the input AC source can cause unbalanced currents and excessive heat in the

drive’s input rectier diodes and DC bus capacitors. Phase imbalance can also damage motors running

directly across the line. The phase imbalance should not exceed 2% of the voltage rating.

Drive HP 1 2 3 5 7.5 10 15 20 25

Transformer kVA 2 4 5 9 13 18 23 28 36

Drive HP 30 40 50 60 75 100 125 150 200

Transformer kVA 42 57 70 90 112 150 180 220 250

BENSHAW RSi S4 Series User Manual

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