# What is difference between armature and no armature in Dc motor ?

#### TimeZero

Joined Sep 14, 2015
18
what is difference between armature and no armature in Dc motor ?
what will happen in the circuit if there is armature and no armature in dc motor?

#### GopherT

Joined Nov 23, 2012
8,009
what is difference between armature and no armature in Dc motor ?
what will happen in the circuit if there is armature and no armature in dc motor?
Either the coils are rotating (armature rotating) and the magnets are stationary (then you need brushes to make contact to the coils rotating on the shaft), or, you have the coils stationary (not called an armature since they are not rotating) and the magnets rotating - this is called a brushless DC motor since no brushes are needed to provide power to the spinning shaft.

#### Hypatia's Protege

Joined Mar 1, 2015
3,226
or, you have the coils stationary (not called an armature since they are not rotating) and the magnets rotating - this is called a brushless DC motor since no brushes are needed to provide power to the spinning shaft.
@TimeZero --- Think 'motorized bicycle generator' -or- continuously sequenced stepper motor (as implemented, for instance, in electronics cooling fans, etc...) -- That said - I doubt DC operation is possible sans commutation -- Note that 'external' commutation schemes (e.g. stepper drivers) do not supply DC to the field windings (as seen over the entire 360° of rotation)

what will happen in the circuit if there is armature and no armature in dc motor?
Assuming the PS parameters and mechanical load are within operational limits, the rotor/armature will turn (IOW: the motors will 'run')...

Best regards
HP

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#### profbuxton

Joined Feb 21, 2014
421
A motor(usually DC) with no armature is a electromagnet. It does nothing but generate an electromagnetic field in the poles.
A motor with an armature if connected and energised as per design will cause the armature to rotate thereby exerting a rotational torque to a load (if load is attached). ie A DC motor will spin a fan,etc,

#### Aleph(0)

Joined Mar 14, 2015
597
That said - I doubt DC operation is possible sans commutation
Too true! Cuz pm rotor and pure DC energized stator without polarity switching is same as pm rotor and pm stator! If that runs you're having free lunch complements to chefs Keely and Mayer

A motor(usually DC) with no armature is a electromagnet. It does nothing but generate an electromagnetic field in the poles
I say electromagnet alone not motor but if it move something like if solenoid or voice coil then _linear_ motor

#### profbuxton

Joined Feb 21, 2014
421
Well,Aleph(0),maybe correct but I have never heard of voice coil being called an "armature', not quite sure what a solenoid core is called, "plunger" comes to mind, probably only for big solenoids like I have seen on brakes for large motors(cranes).
The moving part of relays can be called an "armature" also.
But I do not consider these to be "linear motors". And the question was about DC motors in particular.
Remove the armature from a dc motor and it is no longer a "motor".
As for what happens in the circuit when there is no armature? Depends on the type of dc motor. If it is a series wound motor you will have an open circuit. If it is a shunt connected motor you will just energise the field coils.
Put the armature back in and it will run as a motor. Yippee.

#### Hypatia's Protege

Joined Mar 1, 2015
3,226
pm rotor and pure DC energized stator without polarity switching is same as pm rotor and pm stator! If that runs you're having free lunch complements to chefs Keely and Mayer

#### Hypatia's Protege

Joined Mar 1, 2015
3,226
But I do not consider these to be "linear motors".
Without wishing to appear a 'budinski' -- IMHO solenoids (including true voice coils), linear (as opposed to pivoted) relay actuation mechanisms, 'rail guns', etc... are indeed linear motors -- whereas so called 'voice coil' head positioners, pivoted relay actuators, promotional 'wig-wags' and their ilk represent limited angular motors... Of course it goes without saying that, as a practical matter, 'linear motors' are, in fact, 'rectilinear motors' owing to the necessarily discontinuous nature of their operation...

I have never heard of voice coil being called an "armature', not quite sure what a solenoid core is called, "plunger"
Indeed - such would seem a matter of semantics - It seems 'armature' is variably defined as follows:

1) The moving component of an electro(magnetic)-mechanical device.
2) A moving component of an electro(magnetic)-mechanical device carrying windings.

Whereas a 'voice coil' meets both definitions - a solenoid 'plunger' meets only definition #1 -- Even so said component is frequently referred to as an 'armature' --- On the other hand the 'rotor' of a standard (i.e. unlimited angular) induction motor is seldom termed an 'armature' --- A double irony inasmuch as said component may, from a theoretical standpoint, be regarded as comprising a winding --- Wadda world!!!

And the question was about DC motors in particular.
Remove the armature from a dc motor and it is no longer a "motor".
No arguments there!

Again sorry to 'bud in' -- Seems matters of disputed/ambiguous definition represent irresistible 'fodder' for me -- go figure

Very best regards
HP

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#### profbuxton

Joined Feb 21, 2014
421
Dear Protege, I thank for your pearls of wisdom. No doubt your experience and expertise is vastly greater than my paltry 56 years working in many fields of the electrical industry.
So in MY very humble opinion, a voice coil(speakers or disc drive head positioners) are NOT motors, nor is a solenoid or a relay.
The original question was asking about DC MOTORS. I am not sure how the responses got off track talking about "stepper motors" and "brushless motors" etc.
I say no more.

Ah, by the way I think that's "buttinski"

#### Hypatia's Protege

Joined Mar 1, 2015
3,226
I am not sure how the responses got off track talking about "stepper motors" and "brushless motors"
Speaking for myself, said digression owed merely to the facts that the OP was ambiguous taken with the observation that so called 'DC' brushless motors are, in fact, continuously sequenced stepper motors and hence not truly 'DC' operated at the 'motor level', if you will -- To see this you need only dissect such a device (e.g. a PC PSU cooling fan) to note the embedded 'stepping' (i.e. commutation) electronics...

In all seriousness, if you are privy to a means of continuous, pure DC operation of an electromagnetic motor (of any topology) sans commutation please share! -- Though, as per @Aleph(0), it would seem the implications of such a possibility would necessarily extend to 'over unity'/truly 'free energy'

No doubt your experience and expertise is vastly greater than my paltry 56 years working in many fields of the electrical industry
I apologize that my post must have appeared confrontational and/or condescending? - Such was not my intent! Moreover, my 'expertise' where electromechanical devices are concerned is rather limited -- Anyway, it seems our disagreement{s} are those of nomenclature as opposed to 'substance'?

Again, sincere apologies should my officiousness have offended!

Respectfully
HP

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Joined Jul 18, 2013
28,060
The reason for Brushless DC (BLDC) is the motor represents a DC brushed motor turned inside out, the commutation is any 2 of the 3 stator winding's at any given time.
Max.

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#### profbuxton

Joined Feb 21, 2014
421
My view of DC motors and their armatures is that of course they come with a commutator attached whereon the "brushes" make contact to the armature windings. I also have no knowledge of a "DC motor sans commutation" and never meant to imply such.
As far as PC fans go, even though supplied with DC they incorporate electronics to drive coils in the "stator" al la stepping motors. In my view, I would not call this "commutation". Same applies to "brushless dc motors".

No offense taken. I always find your comments/posts of interest

#### Aleph(0)

Joined Mar 14, 2015
597
As far as PC fans go, even though supplied with DC they incorporate electronics to drive coils in the "stator" al la stepping motors. In my view, I would not call this "commutation". Same applies to "brushless dc motors".
I say commutation in DC motor means switching current and polarity on windings of armature or sometimes stator by mechanical means like with brushes or electronically like with brushless DC motor. So being too technical there is no such thing as purely DC motor But for practicality I say brush commutated motor is real DC motor but brushless DC motor is only called DC because operation transparent to user Plz don't let my opinions anger anyone! I'm just upstart vicenarian lucky to know how to tie my shoes! OBTW I say slip rings not commutator cuz they are not switch!

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#### GopherT

Joined Nov 23, 2012
8,009
Speaking for myself, said digression owed merely to the facts that the OP was ambiguous taken with the observation that so called 'DC' brushless motors are, in fact, continuously sequenced stepper motors and hence not truly 'DC' operated at the 'motor level', if you will -- To see this you need only dissect such a device (e.g. a PC PSU cooling fan) to note the embedded 'stepping' (i.e. commutation) electronics...

In all seriousness, if you are privy to a means of continuous, pure DC operation of an electromagnetic motor (of any topology) sans commutation please share! -- Though, as per @Aleph(0), it would seem the implications of such a possibility would necessarily extend to 'over unity'/truly 'free energy'

I apologize that my post must have appeared confrontational and/or condescending? - Such was not my intent! Moreover, my 'expertise' where electromechanical devices are concerned is rather limited -- Anyway, it seems our disagreement{s} are those of nomenclature as opposed to 'substance'?

Again, sincere apologies should my officiousness have offended!

Respectfully
HP
It is surely a question of semantics - and the location (onboard vs off-board) of the driving electrons. For example, A two-wire PC fan may appear to be DC when examined by most casual observers whereas a three-wire BLDC motor used by model airplane enthusiasts will surely raise eyebrows when trying proper assign polarity to the 3 connections. Especially when common nomenclature deems these motors to be "brushless DC".

Joined Jul 18, 2013
28,060
The modern two wire PC fan is also a 3 wire BLDC with the controller embedded. (see TC653 ic).
The RC outrunners are BLDC where 2 windings are powered at any one time.
Max.

#### Hypatia's Protege

Joined Mar 1, 2015
3,226
I'm just upstart vicenarian lucky to know how to tie my shoes
Indeed! But the big question is -- can you manage a bow-knot sans reference to your smart phone? --- Hey! No offense intended! There are plenty of numpties in my generation too

It is surely a question of semantics
Exactly! --- "Haven't you heard it's a battle of words the poster bearer cried..." (Attribution: Waters? Gilmore? Whoever)

Best regards
HP

PS @Aleph(0) -- perhaps you should identify merely as a 'twenty something' lest folks misread 'vicenarian' and put you down as a 'horse doctor' --- IOW logophilia is best left to logophiles!

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#### Aleph(0)

Joined Mar 14, 2015
597
HP I say your wisecracks need be redressed but OT discourteous to TS so I let it go!