DC Motor "TACHO ERROR": Solutions & Causes

[Gokulkumar]

TL;DR Summary

Dc tacho error speed not in control

Sirs,

Am facing problem in dc drive that is dc tacho fault . I have checked tacho and found values of armature resistance are same in all segments in commutator.
But motor speed not in control. It is automatically varying and suddenly stopped. Is there any bypass method available for tacho feedback ?
Please help me.

 

[berkeman]

Welcome to the PF.

What motor? What controller? What power source (is the power quality good?)?

 

[Gokulkumar]

Is is a dc motor , it's run thro dc drive. There is a feed back signal taken from motor side to drive. Feedback taken from tacho generator. The motor is started slowly and it is running in 50% speed. But suddenly speed going up down . Then alarm came Tach_f. I have checked the tacho generator. But it is good only. Ohmic value is same.
But speed wil going up down and tripped.

 

[Tom.G]

Measure the tachometer voltage while the system is running. When the motor speeds up there are a few possibilities. Here are the most likely I can think of:

1. The tacho voltage rises as the motor speed rises;
   • problem in the drive or in the connection to the drive after where you measure the voltage.
   • if a seperately excited DC motor, then an intermittent field connection.
2. The tacho voltage falls to zero as the motor speed rises;
   • bad tacho
   • or the mechanical connection between tacho and motor
   • or short in cabling between tacho and controller.
3. The tacho voltage falls partially as the motor speed rises;
   • bad tacho
   • or the mechanical connection between tacho and motor.

Cheers,
Tom

p.s. Please let us know what you find, that helps others that have the same problem in the future.