Rockwell Automation 1557 MEDIUM VOLTAGE AC DRIVE - Manual (Page 8)

2-2 INTRODUCTION
1557-UM050F-EN-P – June 2013
An Input contactor with fused isolating switch is optional on the 1557 drive and is only supplied
when specified or if the customer does not have an existing full voltage starter.
The standard 1557 drive is a tachless design. A tachometer is recommended for applications
requiring an output frequency lower than 6 hertz or applications with a starting torque greater than
30%.
A drive isolation transformer or AC line reactor is required with each drive. An isolation
transformer is mandatory when existing motors are used, 12-Pulse line side converters are used,
or for stepping down the main supply voltage. An AC line reactor may only be used when new
motors are used with the proper level of phase to ground insulation. Consult your Rockwell
Automation representative for more information.