245V~255V acceptable from rotary converter?

[Deltic_Engine]

The 30hp Rotary Phase Converter I am using is
putting out 245~255VAC 3-phase (well-balanced).

However the input options of my 10hp (DC Servo Spindle) mill
are 220VAC, 230VAC or 380VAC.

I had PG&E check my line voltage. The Converter mfg thought
it seemed high. The 1-phase input measures 123V, 122v, (245V)
as measured by my PG&E guy. He claimed, in writing,
that this is "excellent".

Questions:
1: When every 3-Ph appliance in the world seems to
specify 220V~230V, why should PG&E consider
245V as "excellent"?

2: Is the resulting 245V~255V from the converter considered high?

3: One seemingly knowledgable web site in Europe claims
that the intentionally higher line voltage ups your utility bill
and that is the main reason why most people's line voltages
are on the high side.
However the PG&E Guy claims just the opposite, that
a higher voltage will lower your bill. So, - Who is right?

4. I have read that one of the 3 legs off a rotary converter
is very suseptable to going under voltage when under load,
so that particular leg should ideally not be serving the
electronics side of a CNC system. Anything to this?

This all relates to a problem I am having:
Even though I am running a 10hp (max) spindle with a
massive 30hp rotary converter (w/good balance) the velocity boards of
the CNC (Fanuc 6MB) will shut down (alarm 401) IF the spindle motor
is accelerated OR decellerated in more than 100rpm increments.
All of the otrher motion control axis works fine/no other errors.

Thanks to all.

[Karl_T]

You have to be careful where you put that "wild leg" on your machine. Don't use it for your control or logic circuits. Many machines use two legs and a step down transformer to get control power. Find this unit and work back to your machine main.

My personal convention has been to ID L1 with black, L2 "wild leg" with yellow, and L3 with red. (I've seen white used on L2, but this is the same as the nuetral color) I keep track of the "wild leg" throughout my shop.

I learned this the hard way when I fried the control board in a Bridgeport servo powerfeed unit.

BTW, to reduce the voltage variation between L1-L2 and L2-L3, run capacitors are commonly used. I had to pay great attention to this to get an EDM machine to perform correctly.

Karl

[fpworks]

I have a similar problem. On my 20hp phase converter, all three legs were 253-254 volts, which was too high to even turn on the machine. (the dealer wouldn't turn on the machine until the voltage was below 240 V)

I checked into our power company's tolerances, and they would allow a pretty wild variation...can't remember, but I think THEIR tolerances allowed up to 260 volts.

Bear with me...I didn't do so well in my EE course in college:

When I asked why our voltage was so high, I was told it was because we were the first building off transformer by the road. They also explained that someone further away may have a slightly lower reading than us, and that they were constantly "tweaking" the voltage due to load on the entire system.

So I've been told, voltage on the high side isn't a bad deal for typical household appliances. More sensitive stuff like televisions, home theater components, and computers all run the AC power through a transformer and really runs off of DC power that is regulated through the power supply, so the AC voltage variation doesn't really affect these. (other than giving the power supply a workout)

As I'm sure you know, in terms of voltage, the phase converter just puts out what it gets in. In our case (and probably yours) it was cheaper to buy some buck boost transformers that knocked down the 3 phase to 230-ish rather than try to tackle the large single phase line going into the phase converter. We bought our transformers from Acme Electric for about $400 (13kVa).

Good luck

Justin

[Deltic_Engine]

Thanks Karl T,
I simply shifted the 3 main power input wires over (musical chairs)
so that the wild leg was not feeding the electronics side of the system.

Wala! still same phase rotation, but now I can go strait from
0 rpm to about 3500 rpm without incurring the 401 alarm.

However that solves only 60% of the problem, because it still trips
the 401 when it accels/decels above the 3500 rpm range (6,000 max).
Basically, I still need to reduce the spindle startup jolt so that it

This means I still need to slow the accelleration and decelleration rate
of the spindle motor.
The spindle seems very abrupt indeed.
On a CNC Mill, there is no reason to suddenly accel/decel a servo spindle
motor up and down in rpm abruptly. There is plenty of time for a spindle to
accel/decell before or after any tool change or operation.
On this particular mill there are at least a couple full seconds available
for that purpose in any scenario that I can imagine.

So, on a GN/Fanuc 6Mb, HOW do I change the accel/decel map for the spindle?
I have looked in the book at all the parameters, but the only
parameter I find that might do this is parameter 140, or 'SANGN',
which is the spindle gain adjustment.

If I suceed in changing the accel/decell map, There is one more
parameter I might have to adjust to compensate for a longer
accel/decel map: 062 'SCTTIM', the delay timer between the speed change
command given and the moment the speed is to be checked/verified by
the controller.

Am I missing any other ways to adjust accel/decel on the spindle?
I would hate to have to have a custom post created to ad a bunch of
incremental 'S' commands to accomplish a single speed change.
Beaing a SERVO spindle I would expect there to be a dedicated adjustment
for this, just as there is on all the other motion control axis.

Thanks