Toshiba ACE-tronics G9 ASD Installation And Operation Manual

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Contents

12 ACE-tronics G9 ASD Installation and Operation ManualLoad-Produced Negative TorqueWhen the ACE-tronics G9 ASD is used with a load that produces negative torque (an overhauling load),the over-voltage or over-current protective functions of the ASD may cause nuisance tripping.To minimize the undesirable effects of negative torque the dynamic braking system may be used. Thedynamic braking system converts the regenerated energy into heat that is dissipated using a brakingresistor. The braking resistor must be suitably matched to the load. Dynamic braking is also effective inreducing the DC bus voltage during a momentary over-voltage condition.If under extreme conditions the dynamic braking system or a component of this system were to fail, thedynamic braking resistor may experience an extended over-current condition. The DBR circuit wasdesigned to dissipate excessive amounts of heat and if the extended over-current condition were allowedto exceed the circuit parameters, this condition could result in a fire hazard.To combat this condition, the 3-phase input may be connected using contactors that are configured to openin the event of an extended DBR over-current condition or an internal circuit failure. Using a thermalsensor and/or overload protection as the 3-phase input contactor drive signal, the contactors will open andremove the 3-phase input power in the event of an extended DBR over-current or system over-voltagecondition. See Dynamic Braking Enable on pg. 140 for more information using Dynamic Braking with theASD.Motor BrakingThe motor may continue to rotate and coast to a stop after being shut off due to the inertia of the load. If animmediate stop is required, a braking system should be used. The two most common types of motorbraking systems used with the ACE-tronics G9 ASD are DC Injection Braking and Dynamic Braking.For additional information on braking systems, see DC Injection Braking on pg. 127 and DynamicBraking Enable on pg. 140.CAUTIONBuy: www.ValinOnline.com | Phone 844-385-3099 | Email: CustomerService@valin.com