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High performance variable frequency drive makes a measurement of the torque through the current to control the brake, for other it's based on speed reference. Then it depend the brake to stand still the motor or decelerate the motor and stop him. When using a DC brake always clearly define what you want to do (stand still or decelerate), then if it's a safety material, then check drive control type.
Common mode currents are motor bearing killers. 1) use as low a carrier frequency as the VFD will allow. 2) make sure that one bearing is grounded and the other is insulated 3) use a dv/dt filter 4) make sure that the bearings installed are proper for the load, roller or ball bearings 5) Use an Aegis or Hedwig shaft grounding device.
DC Motor now a days mostly used for precise speed control of Motor Application,in order to replace the DC motor with AC Induction Motor keep in mind that the initial Torque of the Motor of Load to be Calculate which is to be drive and then fix it the RPM side.
DC motor replace with AC motor its depend on application, some DC motors replace with same rating and some time higher then but mostly there is no issue replace with same motor.
AC reactors reduce harmonics, mitigates transient conditions and helps to maintain proper phase to phase voltages. DC reactors will also mitigate harmonics however it will provide more harmonic attenuation than a equally sized AC reactor.
Both reactors will increase the conduction angle of the DC current pulses flowing through the rectifiers and thereby reduce the harmonics on the supply.
but the inverters must have a common controller. In other words both inverters are controlled by a single system. That isn't specifically 2 separate variable frequency drives on one motor. but similar. However, to operate a single motor from 2 drives is also possible if the variable frequency drives are filtered using a sinewave filter to remove the majority of the carrier frequency.
service VSD blog: A deep observation of automation control industry, especially in AC motor variable speed drive for industrial motor controls.

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