DC tach failure - output 75% of nameplate
DC tach failure - output 75% of nameplate
(OP)
I have a 60v / 1000rpm tach in the control loop for a 30kW DC motor. Recently the printing press that the motor drives has been running faster than rpm gauge is indicating. I have taken a reading of 45v on the tack leads while the motor was running at 1060rpm (measured with an optical hand held tack on the motor output shaft.) the tack is connected to the DC drive and a rpm Gauge. I have disconnected the gauge and achieved the same results. however I can not easily disconnect the tack from the drive. My next step is to replace the tack. the tack brushes, commutator, cable and termination connections are in good condition.
Have you ever seen a tack fail in such a manner?
Past failures of a tack that I have come across are related to brushes and bearings or open windings. This situation seems strange to me!
thanks,
Steve
Have you ever seen a tack fail in such a manner?
Past failures of a tack that I have come across are related to brushes and bearings or open windings. This situation seems strange to me!
thanks,
Steve





RE: DC tach failure - output 75% of nameplate
RE: DC tach failure - output 75% of nameplate
your comments will allow me to purchase a new tach with more confidence that I am not wasting money.
Steve
RE: DC tach failure - output 75% of nameplate
RE: DC tach failure - output 75% of nameplate
RE: DC tach failure - output 75% of nameplate
http://www.goodmart.com/products/Commutator_Maintenance...
http://www.goodmart.com/products/electrical_supplies_co...
http://www.idealindustries.co.uk/index.cfm?pid=17
http://www.usbr.gov/power/data/fist/fist3_14/3_14_1.htm
etc. for more info on commutator maintenance, just in case the commutator is the culprit.
RE: DC tach failure - output 75% of nameplate
Replacement of the Tach was the best fix.
Al
RE: DC tach failure - output 75% of nameplate
RE: DC tach failure - output 75% of nameplate
Did you measure the resistance? (all way round)
RE: DC tach failure - output 75% of nameplate
RE: DC tach failure - output 75% of nameplate