Fanuc spindle drive problem

Linuxcnc is fine, just a drive issue if anyone here has any useful information it would do us a huge favor, it's a friend's cnc. the drive is Fanuc A06B.6055-H112 5000 rpm analog 0 -10 volt practically it works well up to about 2800 rpm absorbing 5 amps per phase 200 volts ac running without load. if this rpm value is exceeded, it explodes and an ultra-rapid fuse blows, always on the same phase. replaced everything works as before but you must not exceed those laps otherwise it jumps again. I would rule out problems with the transistors of the bridge since it runs well and has no permanent damage after the fuse blows. the diodes are fine too, i'm thinking of the 3 scr modules not shutting down properly.
best regards
Mauro

added different schematic but same power components
 

What fuse is it taking out? F5 and F6 look like they protect the SCR bank. The SCR's look like they are set up to regen surplus B+ back to the lines. I don't see the relation to motor speed, the SCRs should be running at 50 or 60 hz. The high speed switching is all done in TM 1, 2 and 3.

blows the 100 amp line fuse F3 always him.
this schematic comes closest to 6055, if nothing else reads better. 
the strange thing is that if you don't go over 2800 rpm it goes on for months without burning anything.

Can you swap SM3 with SM1 or 2, and see if your problem moves?

of course, as soon as I go back to where the cnc is and I recover the suitable fuses.
I think, however, that the permanent magnet servo increases the frequency that the scr have to recover as the revs increase.

I would agree with scotth that SM3 is a likely suspect
or perhaps the gate drive signal to SM3 is bad.

It may be that the SCR regen inverter does not engage at lower
RPMs than 2800

The SCRs probably do run at line frequency as they just steer
the regen current to the proper phase in sync with the line voltage
(the 2 transistors probably do the regen PWM)

ok for the first test I will exchange sm1 with sm3 to see if the fuse on phase r burns instead of T . with the tester the six gates were all equal in value, maybe when I get back on site I'll check the signals with the oscilloscope. F5 and F6 are common 30 amp fast-blow fuses while f1 f2 f3 are 100 amp fuses for semiconductors. I'll have to wait for those, it seems risky to use the normal rapid ones

I went back today to my cnc friend but he decided not to repair his drive also due to the price of the fuses (50€ each) and any spare parts. we saw that it is an induction motor that can be controlled with vfd, having a 2.2 kw 200 volt vfd control techniques at hand we did a test and it behaved very well we turned up to 5000 rpm and also down to a few hz. now we would have decided to take an 11kw ms300 series delta, do you think it is a good choice?
I enclose a photo of the motor plate
thank you very much