Guys, I'm ready to throw in the towel. At one point,m I figured I could just replace all the components, but this thing is so gunked up with potting compound, that is no small feat and with some of the parts becoming hard to find, it is getting risky.

This is just a brushless DC blower fan. The fan assembly is fine and the stator and rotor and windings all seem fine. The controller is what is bad, but I can't seem to fix it and the manufacturer won't repair it, sell me a controller or assist with my own repair. They think I might steal their IP. Ha, if only they read this thread, they'd realize how unlikely that would be!

The controller has all kinds of inrush and thermal protection to keep it from burning up. What about making a new simplified controller and tossing this one. Heck, it doesn't even need to be housed within the same box. It would take AC input and rectify that to DC then use hall sensors to control a cumutator IC to time the firing of each phase. How hard could this really be?

 

What is the motor frame number? May be also called "NEMA" type. The motor frame type should be on the nameplate.

 

Not a standard nema mount. The blower, controller and motor are all custom designed in a single enclosure. The stator is mounted to the same pcb as the controller circuitry. Controller has a lot of bells and whistles I don't need like various protections and variable speed. The simplest controller is all I need. 2 amps, 5000rpm motor with 120V AC supply.

 

Some more links to BLDC motor control;

http://ww1.microchip.com/downloads/en/AppNotes/00857a.pdf

http://www.atmel.com/dyn/resources/prod_documents/doc4987.pdf

Digikey and Mouser carry the IC's.

Why I asked about motor size is, thought maybe you could adapt a standard induction type replacement motor from Grainger. They have several exhaust blower motors.

Don't know about this particular motor, but some motors with a permanent magnet rotor loose magnetism if left out of the stator for too long. The stator keeps the magnetic fields from collapsing.

 

Thank you, shortbus. That's a good idea about trying to fit a new blower. Making one fit might not be so bad. May have to fabricate a braket, but there is plenty of room.

The magnets are strong and the motor did work just fine expect for not wanting to start until I "fixed it".

 

I would use as much of the old blower as possible. May be housing and impeller and mount the new motor to them. That way you change as little as possible. Keep us all advised to what your doing, most people don't post results of the projects.

 

Agreed. The old blower already fits. It has a nice shaft accessible that I could use with a belt if needed. I'm not ready to give up on the motor though. The windings, stator, and rotor are all fine and of high quality. In looking at the heater that this goes in, there is a nice 24VDC power source so I think I'll simplify and just use that rather than rectified AC. It seems like all I need is a simple perf board with three pairs of the similar mosfets to drain to each winding; three hall sensors for position and a microcontroller or off the shelf IC to signal the gates. The chip would read the hall sensors to determine motor position and then signal the gates on the right pair of mosfets. With the micro should be able to control speed or easier just put a pot on the input line. I may need some resistors or caps depending on the IC and hall sensors, but I'm thinking this may be pretty straight forward, assuming I can find some similar circuits that work for ideas and if I use a micro, some code to start with. What do you think?

 

There are stand alone BLDC controllers out there. Have you looked at Ebay yet? Even model airplanes today use them. And some PC printers have gone to them instead of stepper motors. So I'm sure you can come up with something.

 

Yes! I found several "ESC" devices for cheap. They mostly handle high current, but lower voltage for RC cars, planes, etc. They are even simpler than what I imagined as they seem to sense the coil field directly from the supply lines and without hall effect sensors. They have the three wires leading to the wye windings, two wires for DC supply and a control wire harness for speed and direction. Dirt simple.

The circuitry is very simple so I may just build one to suit my requirements.

 

As far as the "lower voltage", by changing to a different mosfet you can get around that. Thats one of the great things about mosfets, they use the same gate voltages for all different values of D-S voltage. No changes to the rest of circuit like BJT's.

 

hey I don't know if you're still kicking this BLDC around, and I remember you mentioning something about building a new controller from scratch. this might help, just ran across it
http://open-bldc.org/wiki/Open-BLDC