Allen-Bradley SMC-50 Quick Start Manual page 22

Chapter 1 Installation
Motor (1) (2)
(1) Customer supplied.
(2) Due to current leakage through an SCR in the OFF state (controller stopped), some form of upstream line power isolation is recommended if maintenance is required on the motor.
See the Isolation Contactor Applications for details.
(3) Bypass must be controlled by an auxiliary contact of the SMC-50 controller that is configured for external bypass.
(4) Bypass contactor must be fully rated to motor Hp/kW and FLA.
NOTE: In addition to a small amount of leakage current flowing through an SCR in the off-state, failure of one or more solid-state power switching components allows uncontrolled
current to flow to the winding(s) of the motor. This could potentially result in overheating or damage to the motor. To prevent potential personal injury or equipment damage,
the installation of an isolation contactor or shunt trip-type circuit breaker capable of interrupting the motor' s locked rotor current on the line side of the SMC-50 controller is
recommended. Operation of the isolation device should be coordinated using one of the SMC-50 controller auxiliary contacts configured to NORMAL.
20
Bypass Contactor with External Overload Protection
All SMC-50 controllers, regardless of power structure, can use an external
bypass contactor with an external overload protection device.
Figure 10 - Wiring Diagram with Bypass Contactor and External Overload
T1/2 L1/1
SMC-50 Controller
T2/4 L2/3
T3/6 L3/5
Bypass Contactor (1) (3) (4)
Overload (1)
Rockwell Automation Publication 150-QS003E-EN-P - April 2017
Circuit
Protective
3-phase AC line power
Device
(1)