Here is a pic of the transformer. Last time I attempted to turn on the circuit breaker, I literally turned off every other breaker in the panel.

 

Here is a pic of the acutal breaker in place as well.View attachment 258202

Tied per NEC. Any one pole might be tripping. Amp-clamp each line to see if there's one that is way more than the others.

 

Here is a pic of the transformer. Last time I attempted to turn on the circuit breaker, I literally turned off every other breaker in the panel. View attachment 258203

That nameplate says it's a STEP DOWN transformer.

Pertinent words are "inrush higher than expected".
http://www.gohz.com/can-a-step-down-transformer-be-used-as-a-step-up-transformer

 

With a "Step-Down-Transformer" Wired in reverse, You will have much higher Idling-Losses and
much higher Magnetizing-Inrush-Current on Start-Up.

Like I said earlier, You need a second Service running at 480-Volts.

Find out what the Wire-Size is on your Service, the 100-Amp Fuses may be incorrect.
I've never seen a 100-Amp 3-Phase-Panel.
.
.
.

 

I believe the wire coming is a #1 wire. It has a boltswitch 100amp disconnect switch at the main that contains the 3 100amp fuses. The main panel and all the is rated for 200amps. Ugh.. Don't want to pull in new service.. I'm not that rich!! LOL

 

Call the xfrmr maker and see if that model can be used in reverse. They typically cannot.
Call water jet folks, see if the jet can be wired for 208v3ph.
Call Larson, see what they have for buck-boost 208-3ph to 480-3ph. 75KVA seems a bit much for a water jet motor.
Last resort, probably simpler, convert jet to 208v3ph.

 

A set of #1-gauge Wires are rated for 150-Amps, (unless they run for more than ~100-feet),
but the Main-Disconnect-Switch will have to be changed-out for a 200-Amp Model.
You didn't state the rated capacity of your Circuit-Breaker-Panel, it may already be a 200-Amp Model.
It would be a bonus to replace it with a "Main-Breaker" style Panel and eliminate all those Fuses.

Also, the 3-Pole Circuit-Breaker that You provided a picture of,
may not be rated for "Motor-Duty", (there's a proper acronym for it but it's been ~30-years).
There are Breakers specifically designed with a Delayed-Trip-Time for Motor-Loads.
.
.
.

 

If the MAIN'S are 100 amp and you're switching a 100 amp load - any other circuitry that might be drawing current will easily put the fuse over limit and blow it. Breakers tolerate higher startup current to a degree. A sustained 100 amp draw shouldn't blow a breaker but it might blow a fuse.

I suspect the issue is just energizing the xfrmr. If it could energize, it's 2.3x more amps (+ some extra for efficiency loss) to go 208 to 480, a 50A load on 480 will easily blow 100A fuses on the primary side.

 

A set of #1-gauge Wires are rated for 150-Amps, (unless they run for more than ~100-feet),
but the Main-Disconnect-Switch will have to be changed-out for a 200-Amp Model.
You didn't state the rated capacity of your Circuit-Breaker-Panel, it may already be a 200-Amp Model.
It would be a bonus to replace it with a "Main-Breaker" style Panel and eliminate all those Fuses.

Also, the 3-Pole Circuit-Breaker that You provided a picture of,
may not be rated for "Motor-Duty", (there's a proper acronym for it but it's been ~30-years).
There are Breakers specifically designed with a Delayed-Trip-Time for Motor-Loads.

Not sure if they need to be spec'd per NEC OCPD for motor, those breakers are not branch ckt breakers, they don't feed motors. They likely are feeder breakers.

#1 is not 150A. 1/0 is 150A copper or 120A aluminum.

Are there any breakers for the 480v side?

 

the fast acting fuses wont suffice, you'll need an RK5 type fuse.

 

the fast acting fuses wont suffice, you'll need an RK5 type fuse.

I think OP needs to go back and see if that step down can be used a a step up.
If ok, change fuse types.
Amp-clamp the line(s) to get an idea of actual inrush. All three to make sure there's no weird imbalance.

 

Well, good news is, those FPE's can be reverse fed, but they note the inrush issue. This is from their catalog.
https://www.usesi.com/media/product-media/catalogs/158625_catalog.pdf

Step-down transformers may be
reverse fed for step-up operation to
increase voltage. This means that
the incoming power is connected to
the low voltage (X’s) and the load
is connected to the high voltage
(H’s). If the low voltage is wye,
the X0 terminal must NOT be connected
in any way. Likewise, if the
low voltage is a delta with a 120
volt lighting tap (high-leg), the X4
terminal must NOT be connected
in any way.
CAUTION: Much higher than
normal inrush currents may occur
with reverse feed operation and
may cause nuisance fuse blowing
or breaker tripping. For this reason,
fuses and breakers with time-delay
characteristics must be used.
If a breaker is used for incoming
over-current protection, it must be a
thermal-magnetic type breaker, not
a magnetic-only type breaker.

 

I think OP needs to go back and see if that step down can be used a a step up.
If ok, change fuse types.
Amp-clamp the line(s) to get an idea of actual inrush. All three to make sure there's no weird imbalance.

typically they can be used up or down. A clamp will not give you a meaningful measurement.

 

typically they can be used up or down. A clamp will not give you a meaningful measurement.

If I clamp a line and set my clamp on inrush, why would it not give me a accurate reading of the amps on the clamped line?

Another Q I have is, should energize amps be pulling ~100A+ inrush on all three lines, or even that much on any input line?

 

No breakers on the 480v side, just a 60 amp disconnect switch before the waterjet. So the RK5 fuse looks like a bigger fuse than what's allowable in the disconnect I have at the main. Is it possible that BOLTSWITCH makes an RK5 type fuse holder or how would I go about that??

 

If I clamp a line and set my clamp on inrush, why would it not give me a accurate reading of the amps on the clamped line?

Another Q I have is, should energize amps be pulling ~100A+ inrush on all three lines, or even that much on any input line?

Ok, if your meter has that function, you'll have a reading.
Fast acting fuses will blow in this application. I don't need a meter to tell me that.

 

No breakers on the 480v side, just a 60 amp disconnect switch before the waterjet. So the RK5 fuse looks like a bigger fuse than what's allowable in the disconnect I have at the main. Is it possible that BOLTSWITCH makes an RK5 type fuse holder or how would I go about that??

can you draw a single line schematic from service infeed to load.

 

No breakers on the 480v side, just a 60 amp disconnect switch before the waterjet. So the RK5 fuse looks like a bigger fuse than what's allowable in the disconnect I have at the main. Is it possible that BOLTSWITCH makes an RK5 type fuse holder or how would I go about that??

No OCPD on the 480v3ph branch ckt? Isnt that a violation of NEC? The disco is a non-fuse type?

And for clarity, is it blowing fuses on xfrmr energize (secondary no-load), or when you apply motor load on 480v?

What's the Amp rating of the waterjet system? Is 480v3ph balanced on load?
Any known PF for the waterjet system? Is 75kva robust enough? If the PF is not so good, PF correction caps may help things.

 

I may have worded it incorreclty. there is a 60 amp fused safety switch between the waterjet and transformer. Here is crude drawing of the layout.
Yes it blows on the the xfrmr energize(secondary no load). So I took a pic of the motor.. Maybe I do just nuke the transformer and run it off 208 if the transformer is going to be an issue.

 

I may have worded it incorreclty. there is a 60 amp fused safety switch between the waterjet and transformer. Here is crude drawing of the layout.

Are there any other circuits coming off of the service disconnect, or does it run directly to the the panel board?