Re: SepEx complexity (was: bus voltage 300V)

[Rod Hower <rodhower@ameritech.net>]

In addition, the electronics and controls
needed to make a moveable brush system would
be more expensive and less reliable than an AC system.
The cost of semiconductors has been reduced to the point
that they are competitive with DC systems.
You must consider the lifetime cost of the system
to fully realize this cost comparison.  This is working
its way into forklifts, but cost benifits of an AC system
below 48Vdc are still difficult.  I suspect golf carts
will remain DC for at least another 5 years, but sand or silicon,
will altimately win in the future.
Rod

Victor Tikhonov wrote:
> Rod Hower wrote:
> 
>>Lee is correct about the bungling on this motor.
>>I have always suspected there is a design flaw.
>>Regardless, a Sepex motor relies on field weakening
>>to get high RPM's.  It is also easy to regen with a
>>sepex motor.  One thing that is a problem with sepex
>>motors is the inability to change brush advance.
>>This is a big problem when operating over a wide
>>torque speed curve and a bigger problem when you try
>>to regen (when the brushes would rather be at a different
>>orientation than motoring).
>>The major advantage of the AC motor is the control can
>>effectively change brush timing (OK, there isn't brushes,
>>but electrically its the same).
>>So a properly designed AC system does have an advantage over
>>the DC since the motors peak performance point can be optimized
>>better with the electronic controller.  I'll admit that there
>>may be design problems with the GE sepex motor, but it still
>>cannot produce the wide torque speed curve of an AC control system
>>unless it has a mechanical assembly that can change brush advance.
>>I may not get an "agree" from Lee on this, but I would like to
>>compare how a sepex design without moveable brushes can match
>>the performance of an AC system.
>>Rod
> 
> 
> Performance on the test bench *may* match but tral life reliability
> of mechanicly movable plate will never match reliability of
> AC motor with one movable and contactless part - rotor.
> 
> We Always say electic motor has one movable part, when comparing
> to ICE, but to be clear (comparing AC with DC), ADC motor has 5 moving 
> parts - rotor abd 4 brushes sliding inside brush holders. Reliability 
> will be lower than thet of AC machine. May not be much, but lower. Add 
> to it movable plate and it's yet worse than that: wear of rails it moves
> and can jam in, electronically controlled actuator needed (another 
> stepper motor moving the plate, or, in worst simplest case, consuming 
> power solenoid). No matter what is the solution it's adding stuff 
> (movable or not) to already more complex DC motor.
> 
> Victor
> 
>