DIY Harbor Freight Air Filter

[Toker1]

You must mean on an insulated motor, right? Lol
Well I only agreed with the mechanical turning requirements like 3 times on this thread now. Clearly you are not reading my comments. Or maybe your exhausting experience has blinded you temporarily. I’m not really sure how to continue a conversation with someone who is able to speak but unable to listen.
Do you agree that rotating coils have an induced emf? Because, in motors this phenomena is called back emf because it opposes the emf input to the motor. At least you are admitting this does exist finally. Took a while considering how experienced you claim to be.

 

[MJTECH]

All motors have insulated wiring or they would fail, however there is no such thing as an insulated motor.

Common motor types.
AC Brushless Motors.
DC Brushed Motors.
DC Brushless Motors.
Universal Motors.

The most common AC Brushless types are, shaded pole which is what is used in that blower, capacitor run, commonly used in A/C units for condensers and compressors and ECM's used in A/C units for evaporators, and while ECM's have permanent magnet rotors, none of these motors are capable of generating power.

The reason these motors cannot generate power is they only have a rotating coil when power is applied to the field winding, the field windings induce power into the buried copper strips in the rotor, magnetizing the steel lamination's of the rotor, which produce a counter EMF causing the rotor to rotate, however that counter EMF is too weak to produce any back fed power into the windings, it is an energy absorber, not a energy generator.

The only type of motor capable of generating power is a motor with a armature and a commutator, such as a universal motor, which are commonly used in power tools and many vacuums, these motors if connected to a source of mechanical motivation will generate power to a limited degree, but due to the angle of phase that the brush's are set at they will produce considerable less power then what an electrically magnetized rotor of a standard generator can induce into the field windings.

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[Toker1]

I’m not talking about the wires. Power control devices may consist of bipolar transistors. Some are more insulated than others (depending on the rating). Ok... I wasn’t very clear and I apologize for making such a blanket statement like that. Properly insulated motor would be better terminology.
My comment should have read, assuming the insulation is enough to prevent. But we never discussed exactly how much electric we are discussing. If there is enough voltage, you can easily overwhelm the insulation in that case.

 

[MJTECH]

Insulation classification is a rating and is applicable to all motors, and if the insulation rating is exceeded the motor can be damaged, sometimes rather violently.

Ratings are Class: A=105°C, B=130°C, F=155°C, and H=180°C.

Then there are voltage ratings, common in the U.S. are 120/240, 277, and 480 VAC, specialty motors such as for locomotives are rated for 600 VDC and 600 VAC 3 Phase in the newer General Motors EMD units.

When insulation breaks down strange things can happen, I installed a rebuilt 3 phase 480 volt 500 hp motor for Waste Management in Pompano beach, the re-builder Hi-Potted the motor and certified as ready to go, I went into the control room, my guys closed the power into the motor controller and stood in the clear, I started the motor and there was a violent explosion, which shook the control room.

I looked out of the control room which was up on a superstructure and noticed the power was out for blocks around the area, oops.

I stepped outside, my guys opened the power to the motor, the three time lag fuses had opened as well and we put out the fire the motor started.

The motor was sent out for a forensic examination, turned out the re-builder failed to properly secure a turn of the windings, the startup magnetic forced ripped the copper windings out of the field and it made contact with the rotating rotor and the subsequent arc burned more windings hard bolting all 3 phases to ground.

Somewhere up in Juno Beach an FP&L technician in their control center was probably wondering what just happened down in Pompano.

Thirty grand down the drain, but not out of my pocket.

 

[Toker1]

Hells bells! 500hp is HUGE!! I could only imagine what that sounded like. I have been in a scary situation like that before. We were generating power using a Rankin cycle. The pressure built up inside the closed loop system. The emergency PRV burst and the plant walls were shaking pictures off onto the floor.
My boss ducked under the control room table and was reaching above his head to hit the emergency stop over and over.
Luckily no one got injured. A big lesson on how hot/cold in the wrong location can be quite destructive.