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Jamie

wrote:

Dear sir,

we are useing 4Q dc drive SSD make for 700 hp rolling mill
application .This motor for mill.We are faceing problem when ever
power dip occured incomming fuses of 3 phase fuses falure freqently
and alarm showing in drive speed feedback.we are useing incomming
thyrestor fuses.
how to eleminate this problem?

1.
You may need an isolation xformer for the drive from the mains.
You could have a problem with your motor shorting in the armature
to ground.

2.
The alarm in the drive is indicating you have a stall out. this
could be due to a machine jam up or, like I said, armature shorting
in the motor when it gets hot, or could be a bad encoder that is
allowing the mill to run away and over currents. This could also mean
in proper set of the drive allowing high currents above the fuse
protection.

Check the motor with a megga meter for shorts. it should be
well above 2 megs when the motor is hot.

3.
You have a bad bridge in the drive that is shorting when hot or,
you have a miss fire in the firing circuit and could be due to buss
shorting.

measure your 3 phase voltage from each leg to ground to start with.

Make sure the current limiting in the drive is set below the fuse
ratings and do not have the drive ignore the error.

http://webpages.charter.net/jamie_5"