Hello,
Please correct my terminology, it seems that 3 or 4 terms are used for the same Diode/Motor configuration.
Automotive application, i.e. ~200F under-hood temps.
Air conditioning blower motor, and/or, electric radiator fans.
Motors are crude, brute force, inefficient, brushed, permanent magnet, with a high inertia flywheel type load on start-up.
26 to 28 amps DC, 12 to 14 volts on high speed,
(heavy, forced-air-cooled, open wire-wound resistor, for speed control)...... OR
( series/parallel relay contraption for 2 speed operation,
(actually works quite well, as long as you have 2 motors working in tandem with each other ) ).
Filtered with 33,000 mfd capacitor, per-each motor,
(capacitors mounted inside where it's always cool, using way too much 14ga. wire).
IXYS Power Schottkey Rectifier DSS 60-0045B Data Sheet = http://ixapps.ixys.com/Datasheet/L127.pdf
IFAV = 60 A
VRRM = 45 V
VF = 0.57 V
The Problem....
I would like to cut electrical noise from the brushes, and
hopefully extend brush life and "maybe" get a slight power output gain,
from my heavy under-hood motors. (5 of them),
(the alternator is easily up to the task of providing
twice the required current while maintaining exactly 14 vdc under all conditions).
This pursuit started years ago when I spent
quite a bit of time trying to build PWM controllers for similar motors.
At which, I was a repeated, dismal, failure,
with loads of the evil blue smoke squirting from every semiconductor.
(Sometimes with a spectacular display)
And, I think that "one" of the stumbling blocks was finding the correct diodes to protect the MosFets.
I have since come up with several other, "not quite as satisfactory", methods of speed control.
I have recently dabbled at addressing this situation again,
and thought I would finally ask for some suggestions.
The above referenced Power Schottkey's seem to be well over-rated for the job,
but I'm obviously not taking some, or many, factors into consideration.
These diodes, when close connected to the motor(s),
produce no detectable temperature rise with the motors at full load, and
with repeated start/stop cycling, with NO heat-sink.
Even so, I mounted them to a small heat-sink made of 1/8th inch aluminum angle,
approx. 1"x 1"x 3" long, with proper heat-sink compound.
They consistently fail, in a shorted condition,
after around ~10 to ~15 hours of run time at ~160 to ~180F ambient temps.
( My engine control computer is factory mounted under the hood as well,
with zero failures in 15 years )
I could possibly fan cool them down to around ~120F.
( PWM alternator field winding noise ??? maybe ?? )
I would prefer to not have to mount them inside the cab of the truck along
with their attendant trash radiating wiring. (twisted 16ga. stranded wires)
This may be some-what silly, in that, I don't really have any noise related wiring problems.
But I'm still kinda stuck on making this a more elegantly engineered, and operating,
motor control system.
The commercially available solutions have many limitations, or exorbitant price tags.
I do not have much in the way of test equipment, or really even the time to
properly teach myself how to properly design such a system, so any
suggestions would be greatly appreciated.
I hope I am providing someone with a unique challenge that they find satisfying,
I know I've spent crazy hours helping others (in different fields) so
I feel I'm deserving of some help back. Thank You for your consideration .
Jim
Please correct my terminology, it seems that 3 or 4 terms are used for the same Diode/Motor configuration.
Automotive application, i.e. ~200F under-hood temps.
Air conditioning blower motor, and/or, electric radiator fans.
Motors are crude, brute force, inefficient, brushed, permanent magnet, with a high inertia flywheel type load on start-up.
26 to 28 amps DC, 12 to 14 volts on high speed,
(heavy, forced-air-cooled, open wire-wound resistor, for speed control)...... OR
( series/parallel relay contraption for 2 speed operation,
(actually works quite well, as long as you have 2 motors working in tandem with each other ) ).
Filtered with 33,000 mfd capacitor, per-each motor,
(capacitors mounted inside where it's always cool, using way too much 14ga. wire).
IXYS Power Schottkey Rectifier DSS 60-0045B Data Sheet = http://ixapps.ixys.com/Datasheet/L127.pdf
IFAV = 60 A
VRRM = 45 V
VF = 0.57 V
The Problem....
I would like to cut electrical noise from the brushes, and
hopefully extend brush life and "maybe" get a slight power output gain,
from my heavy under-hood motors. (5 of them),
(the alternator is easily up to the task of providing
twice the required current while maintaining exactly 14 vdc under all conditions).
This pursuit started years ago when I spent
quite a bit of time trying to build PWM controllers for similar motors.
At which, I was a repeated, dismal, failure,
with loads of the evil blue smoke squirting from every semiconductor.
(Sometimes with a spectacular display)
And, I think that "one" of the stumbling blocks was finding the correct diodes to protect the MosFets.
I have since come up with several other, "not quite as satisfactory", methods of speed control.
I have recently dabbled at addressing this situation again,
and thought I would finally ask for some suggestions.
The above referenced Power Schottkey's seem to be well over-rated for the job,
but I'm obviously not taking some, or many, factors into consideration.
These diodes, when close connected to the motor(s),
produce no detectable temperature rise with the motors at full load, and
with repeated start/stop cycling, with NO heat-sink.
Even so, I mounted them to a small heat-sink made of 1/8th inch aluminum angle,
approx. 1"x 1"x 3" long, with proper heat-sink compound.
They consistently fail, in a shorted condition,
after around ~10 to ~15 hours of run time at ~160 to ~180F ambient temps.
( My engine control computer is factory mounted under the hood as well,
with zero failures in 15 years )
I could possibly fan cool them down to around ~120F.
( PWM alternator field winding noise ??? maybe ?? )
I would prefer to not have to mount them inside the cab of the truck along
with their attendant trash radiating wiring. (twisted 16ga. stranded wires)
This may be some-what silly, in that, I don't really have any noise related wiring problems.
But I'm still kinda stuck on making this a more elegantly engineered, and operating,
motor control system.
The commercially available solutions have many limitations, or exorbitant price tags.
I do not have much in the way of test equipment, or really even the time to
properly teach myself how to properly design such a system, so any
suggestions would be greatly appreciated.
I hope I am providing someone with a unique challenge that they find satisfying,
I know I've spent crazy hours helping others (in different fields) so
I feel I'm deserving of some help back. Thank You for your consideration .
Jim