[Milsurplus] Even Worse

[Peter Gottlieb]

Darkening Cambridge wouldn't be the best PR move.

What a crazy setup.  These days they use a single large VFD to do this 
job and just set current or power limits.  It wouldn't be hard to even 
incorporate a data feed from Cambridge electric which specified every 4 
seconds how much power they could pull.  That would even help smooth out 
grid fluctuations.

This same problem exists in Chile with the big mines.  You don't just 
pull in a contactor to start a 20,000 horsepower crusher motor.

Peter



J. Forster wrote:
>> All the dynamics of all the control systems across the grid can make for
>> an "interesting" day if something goes wrong.
>>     
>
> The general philosophy seems to be "don't rock the boat". In Fitzgerald's
> grad school electrical machinery course, we went on a tour of the MIT
> Bitter National Magnet Lab, which has giant AC motors hooked to DC
> generators for powering the experiments. These things were easily 15 feet
> in diameter with buss bars like I beams.
>
> Anyway, when they put the machines on-line, they would gradually bring
> them up to operating speed with smaller motors and look at the phase
> difference with a thing like a differential synchro hooked to a dial. The
> pointer would turn CW or CCW, depending on whether the machine was above
> or below sync speed. When the pointer was stationary, the machine was
> operating at the right speed. Then they would goose it a bit up or down to
> bring the phase difference to zero, and then adjust the field to match
> voltages.
>
> The final step was to connect the thing to the grid with a giant circuit
> breaker.
>
> The objective was to be as seamless as possible. A screwup and the city
> would go dark.
>
> Best,
>
> -John
>
> ================
>
>
>
>   
>> Generally, most plants are looking to have a 1.0 PF at their point of
>> connection to the grid even if it takes significant reactive to get there.
>>
>> (Yes, I know, gross oversimplification).
>>
>>
>>
>> J. Forster wrote:
>>     
>>> By raising or lowering the field current, you can make the reactive
>>> power
>>> look capacitive or inductive respectively, but not instantaneously. The
>>> L/R time constant of the field circuit is nowhere near zero. The L is
>>> huge.
>>>
>>> -John
>>>
>>> ===============
>>>       
>
>
>
>