tailshaft56
Well-known member
I could be wrong but I seem to remember some power tools used come with Universal moter which would run on ac or dc.
110 volt DC motor where was it used
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I like the discussions, you can always learn something from it, as anything goes on the internet, filter it and take it in with a grain of salt. That is how people learn from discussion and collaborations of ideas. I am pretty sure there are some real power engineers here and there and probably everywhere. Doesn't matter, if they are not contributing they are just as dead to me as a doorknob in some cow's ****, just saying. Only people that don't filter and process information is the follower of cults and brainwashed zombies.
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I tried running DC to my HF / Craftsman / ridgid grinders, it runs. but at 12V it's weak. Pretty sure one of these days I can try to run it straight off unfiltered isolated 120V DC.
as far as universal motors, I follow this guy on youtube he has some great explanation on motors.
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rburke65
Well-known member
TractorJeff....I think you just said a mouth full.
Well you sure did spark up a conversation.
I'm still trying to find where you saw in the OP's motor nameplate indicating any value for phase.
The phase field on the OP's motor nameplate is blank as I would expect for that vintage motor. Transistors weren't even invented in that day. BLDC technology occurred 70+ years later than the OP’s motor was built.
As for the rest of the conversation, many correct things stated about the technology and electrical fundamentals.
Where I see a big difference is the ability to recognize an ac waveform that originates from a dc waveform.
As for the technology/marketing hook of “3 phase dc” motors, etc., the BLDC is just the current-day reinvention of the brushed dc motor leveraging some ac induction motor concepts and additional hardware to do so. The motor stator winding went from 1 winding to 3, added hall effect sensors and logic to determine phase order firing for initial direction and sustained commutation, removal of brushes and commutator and now has a rotating magnetic field due to the selective firing of the output stage with 3 pairs of IGBTs.
If someone were to hang a scope on the output of this black box (BLDC motor drive), they would quickly see 3 waveforms each with:
A Periodic frequency
A square wave
A Periodic change in the polarity of the square wave – with identical times and durations
Maintained phase shifts between outputs
……all the makings of a ac signals.
The observed outline of the waveforms would appear a little coarse/dirty due to the pulse width generation method used in the drive.
More power would also be observed concentrated in the center of each ½ period and less on the start/end.
As the time base on the scope is decreased, it would be obvious to further see the makeup of each periodic waveform is individual pulses.
These groups (each ½ squarewave) of dc pulses would have the following characteristics:
Occurring at a Periodic frequency (rising edge)
Pulses of varying widths but constant amplitude
A Periodic change in polarity
Phase shifts between outputs
So using the controller logic and IGBT’s, DC voltage has been compiled to create an AC output – one that is periodic, 3 phase, symmetrical to the axis and closely approximates a sinusoid >>> aka - a 3-phase ac signal.
wyliesdiesels
Well-known member
Well you sure did spark up a conversation.
I'm still trying to find where you saw in the OP's motor nameplate indicating any value for phase.
The phase field on the OP's motor nameplate is blank as I would expect for that vintage motor. Transistors weren't even invented in that day. BLDC technology occurred 70+ years later than the OP’s motor was built.....
If you look closely at the pic, it appears someone etched a 3 in the phase field...this is what has sparked this thread....
If you look closely at the pic, it appears someone etched a 3 in the phase field...this is what has sparked this thread....
Ah ok, I thought is was a ding. But still for that vintage motor - no way.
In that era, they were still fighting over who was AC and who was DC.
ttpete
Well-known member
That motor is part of a fabric cutter used to cut out material in a clothing factory. It's a handheld tool with a DC motor that will also operate on AC, just like any other electric hand tool like a drill motor or die grinder.
Toothaker
Well-known member
DC doesn't have a waveform - it has neither pure sinusoidal or simulated waves, regardless of their shape. DC is a flat line on a scope. "Phases" are a reference to the various waves' relationship to each other - Alternating Currents have a sinusoidal wave.
Again, phase has no place when talking about Direct Current.
Making the conversation drift into a conversation (argument?) about various conversions of AC to DC, AC to DC to AC, DC to AC, etc. is not clarifying things, and it doesn't make the above facts different.
Again, phase has no place when talking about Direct Current.
Making the conversation drift into a conversation (argument?) about various conversions of AC to DC, AC to DC to AC, DC to AC, etc. is not clarifying things, and it doesn't make the above facts different.
wyliesdiesels
Well-known member
I use to mess with oscilloscopes in high school electronics but forgot a lot of it.
But i know that DC does not have phases.
Looks like the believers havent come back to rebuttal...
foolishpride
Well-known member
The 125VDC control voltages you see in medium and high voltage switchgear comes from your station batteries. These batteries supply the trip potential to the protective relays to operate the breakers.