GE DC300 Drive - Fuse Failure

Sounds like an inverting fault.

-check for commutator damage, the com may have flashed. There may be pieces chewed off the tips of the com bars.

check for:

-Low AC line

-intermittent AC power (do you have travelling contacts?)

- SCR faulty

-poor gate firing

-Armature voltage too high due to field control issues

-check for both fwd and reverse bridge operation, no missing pulses

That's just the start of the troubleshooting.

Good thing is, something is just broken.

1.The out put of drive is 500V D.C where the two motors armature are connected in series. 2.Supply is fixed cable only there is no traveling part either side.(Voltage level is good) 3.Meggered both the motors values are good. 4.Failures always happen only in reverse mode of operation (Regenerative mode) 5.Drive rated ampere is 825 Amps, fuse provided is 800A. 6.Some times two phases fuse blown out and some time only one phase fuse blown out.

My memmory is slipping. Are there six sets of fuses (leg fuses) in this bridge, or three sets (line fuses)?

It still sounds like an inverting fault. (see first response)

For a 500V armature you probably have a 460vac line. It must be stable.

Many cranes will use the field range of the motors. If there are field control issues the armature volts may climb too high.

I assume since you indicate 2 motors in series you have checked the field current in both motors. (Are the fields also series connected?) Check the voltage across the field windings to make sure you don't have shorted windings.

Record the armature voltage and current during a fault. That can be set up with a digital scope, triggerred by high amps. Have a pre-trigger of about .5 seconds, 1 second sweep, to see what leads upto the fault.

Was the drive system running at high speed before it tripped?

Have there been any recent motor changes?

By the way, I suggest you sign in and let us know who and where you are.

This sounds a lot like a container crane I am currently troubleshooting in Vancouver, Canada.

But the one I am working on has blown three 500KW armatures. Two armatures appear to be re-wind manufacturing defects. The third armature (the first fault) appears to have faulted in the mica insulation inside the inboard V ring of the commutator. That took a burnout of the armature to find the ground fault.

1.Yes the input voltage to the drives 500V A.c thru one MCCB and Three 800A fuse in the drive. 2.Some times the incomer breakers also trips, 3.The field winding also series only ( resistance very low around 0.1ohms) 4.The armature resistance is around 8.1 ohms. 5. There s one Protector circuit at the input side consist of MOV's and RC Circuit combination. 6.No recent changes in Motor or any work carried out on the motor.

I hope you have armature and field resistances mixed up.

Please provide NP data from motors.

How often do you have the faults?

Hoist Motor, Make:GE, HP : 230, DUTY:CONT, Volts : 250 , Amps : 765 , RPM : 650 / 1790 , Arm resis : .0099 , Sh.Field Resis : 28.3 Ohms , Sh.field Data : 240 Volts , 7.38 / 2.48 Amps. The failure of fuse was once in two days and breaker trips daily, this pbm exists from last one week only...

If the two motor fields were wired in parallel then you should measure about 14 ohms at the drive. (two 28.3 resitances in parallel)

Until you give us a dwg of the drive to 2 motors connection it appears you have a shunt field failure.

To prove this, go to the motors and open the conduit boxes. Tell us how F1 F2 (F11 F22 if exist) are connected. Open the connections and measure the winding resistance at the motor. Compare both motors to each other. The resistances F1-F2 should equal F11-F22 , and match the second motor. The series connection resistance from F1 - F22 should equal 28.3 ohms. Be aware your meter may indicate a lead resistance of up to another ohm, so check your meters shorted lead resistance also.

With a shorted field your armature amps will be too high trying to develope torque.

If the drive current limit is incorrect or the MCCB setting is very close to it, you may trip the breaker.

After replaced the control relays in the Drive panel recently no failures now the operation s stabilized. Thanks for u r support...

Good to hear it has stabilized.

I've never seen a DC motor that has lower resistance on its field than on its armature winding, so, hopefully you have them wired wrong.

But in case that's ok; try going here and download the manual, or try this other link.

Yahlasit

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