Is It CW or Is It CCW?

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taylorp

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All right Ladies and Gentlemen:

I am throwing this out because we are arguing within our group over how to designate the rotation of AC motors in our communications. Is rotation determined from the shaft or driven end, or is rotation determined from the ?opposite driven end.?

I know the NEC doesn't specify this, but it is interesting to hear the guys and gals in my group argue over the subject.

I am sure this subject has been discussed before, but I felt that a timely discussion on how you determine rotation would be a benefit to all.

What say ye Code Forum ?experts??

P.S. My point in the argument was that rotation depends on which end of the motor you are looking at and simply saying CW or CCW doesn?t mean anything.
 
taylorp said:
P.S. My point in the argument was that rotation depends on which end of the motor you are looking at and simply saying CW or CCW doesn?t mean anything.
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You are correct. We always specify rotation AND from which end. To much room for confusion just to specify CW or CCW.
 
This is taken from a spec on an actual project and is usually how it is specified here:
Direction of rotation: COUNTER CLOCKWISE(Facing the motor drive end shaft)
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Drive end.
 
Hydraulic pumps and motors

Hydraulic pumps and motors

We backwards (for whom NFPA is National Fluid Power Association) folks still use "right hand" and "left hand" ... looking into the driving shaft for a pump, output shaft for a motor. Thus a (most common industrially) RH pump would be driven by a motor rotating CCW. Equipment from European manufacturers is commonly seen; they seem to follow this as well, but often use ACW rather than CCW in their descriptions.
 
GeorgeB said:
We backwards (for whom NFPA is National Fluid Power Association) folks still use "right hand" and "left hand" ... looking into the driving shaft for a pump, output shaft for a motor. Thus a (most common industrially) RH pump would be driven by a motor rotating CCW. Equipment from European manufacturers is commonly seen; they seem to follow this as well, but often use ACW rather than CCW in their descriptions.
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George, I have heard this same terminology used, however it does not seem to be commonly used among electrical persons today.
 
And I might add that I was taught by some "old timers" that the most common way of looking at rotation was from the driven end, or shaft end. But I have heard other "old timers" dispute this.

It seems that the different National and International organizations would get together and declare once and for all where to determine the rotation of a motor. Kind of like which side of the road to drive on. (oops, that was a dumb example.)
 
Above ground:
L1-L2-L3 = CW as viewed from the shaft end.

Submersible:
L1-L2-L3 = CCW as viewed from the shaft end.
 
Here's some clipped text from NEMA MG1-2003, Revised 1-2004. This standard has been replaced several times since published, but I don't own any.

Section I
GENERAL STANDARDS APPLYING TO ALL MACHINES
Part 2
TERMINAL MARKINGS
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2.3 DIRECTION OF ROTATION
2.3.1 Alternating-Current Machines
See 2.24.

2.3.2 Direct-Current Machines
See 2.12.

2.3.3 Motor-Generator Sets
When one motor and one generator are coupled together at their drive ends, the standard direction of rotation for both machines shall be as given for that type of machine and will apply to the motor generator set without a change in connections.

The correct direction of rotation shall be clearly indicated on a motor-generator set.

When two or more machines are coupled together but not at their drive ends, the standard direction of rotation cannot apply to all machines in the set. Changes in connections will be necessary for those machines operating in the opposite direction of rotation.

DC MOTORS AND GENERATORS

2.10 TERMINAL MARKINGS

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2.10.3 Armature Leads_Direction of Rotation
All numerals shall be determined on the following fundamental basis. the numerals of all the terminals of direct-current machines shall be selected so that when the direction of current in any single excitation winding is from a lower to a higher numeral, the voltage generated (counter electromotive force in a motor) in the armature from this excitation shall, for counterclockwise rotation facing the end opposite the drive, make armature terminal A1 positive and A2 negative. With excitation applied in the same manner, the opposite rotation will result in A2 being positive and A1 negative.

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2.12 DIRECTION OF ROTATION

2.12.1 Direct-Current Motors
The standard direction of shaft rotation for direct-current motors shall be counterclockwise facing the end opposite the drive end.

The direction of shaft rotation of direct-current motors depends on the relative polarities of the field and armature and, therefore, if the polarities of both are reversed, the direction of rotation will be unchanged. Since the field excitation of direct-current motors is obtained from an external source, residual magnetism has no practical effect on polarity except for those with permanent magnet excitation. Reversal of the shaft rotation of a direct-current motor is obtained by a transposition of the two armature leads or by a transposition of the field leads. With such reversed shaft rotation (clockwise) and when the polarity of the power supply is such that the direction of the current in the armature is from terminal 2 to terminal 1, the current will be flowing in the field windings from terminal 1 to terminal 2, and vice versa.

2.12.2 Direct-Current Generators
The standard direction of shaft rotation for direct-current generators shall be clockwise facing the end opposite the drive end.

The direction of rotation of a generator mounted as a part of an engine-generator set is usually counterclockwise facing the end opposite the drive end.

Self-excited direct-current generators, with connections properly made for standard direction of shaft rotation (clockwise), will not function if driven counterclockwise as any small current delivered by the armature tends to demagnetize the fields and thus prevent the armature from delivering current. If the conditions call for reversed direction of shaft rotation, connections should be made with either the armature leads transposed or the field leads transposed. The polarity of a self-excited direct-current generator, with accompanying direction of current flow in the several windings, is determined by the polarity of the residual magnetism. An accidental or unusual manipulation may reverse this magnetic polarity. Though the generator itself will function as well with either polarity, an unforeseen change may cause disturbance or damage to other generators or devices when the generator is connected to them.

2.12.3 Reverse Function
A direct-current machine can be used either as a generator or as a motor if the field design is suitable for such operation. (The manufacturer should be consulted regarding this.) For the desired direction of rotation, connection changes may be necessary. The conventions for current flow in combination with the standardization of opposite directions of rotation for direct current generators and direct-current motors are such that any direct-current machine can be called _generator_ or _motor_ without a change in terminal markings.

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AC MOTORS AND GENERATORS

2.20 NUMERALS ON TERMINALS OF ALTERNATING-CURRENT POLYPHASE MACHINES

2.20.1 Synchronous Machines
The numerals 1, 2, 3, etc., indicate the order in which the voltages at the terminals reach their maximum positive values (phase sequence) with clockwise shaft rotation when facing the connection end of the coil windings; hence, for counterclockwise shaft rotation (not standard) when facing the same end, the phase sequence will be 1, 3, 2.

2.20.2 Induction Machines
Terminal markings of polyphase induction machines are not related to the direction of rotation.

2.21 DEFINITION OF PHASE SEQUENCE
Phase sequence is the order in which the voltages successively reach their maximum positive values between terminals.

2.22 PHASE SEQUENCE
The order of numerals on terminal leads does not necessarily indicate the phase sequence, but the phase sequence is determined by the direction of shaft rotation relative to the connection end of the coil winding.

2.23 DIRECTION OF ROTATION OF PHASORS
Phasor diagrams shall be shown so that advance in phase of one phasor with respect to another is in the counter-clockwise direction. See Figure 2-14 in which phasor 1 is 120 degrees in advance of phasor 2 and the phase sequence is 1, 2, 3. (See 2.21.)

2.24 DIRECTION OF ROTATION
The standard direction of rotation for alternating-current generators is clockwise when facing the end of the machine opposite the drive end.

The direction of rotation of a generator mounted as a part of an engine-generator set is usually counterclockwise when facing the end opposite the drive end.

The standard direction of rotation for all alternating-current single-phase motors, all synchronous motors, and all universal motors shall be counterclockwise when facing the end of the machine opposite the drive end.

AC GENERATORS AND SYNCHRONOUS MOTORS

2.25 REVERSAL OF ROTATION, POLARITY AND PHASE SEQUENCE
Alternating-current generators driven counterclockwise when facing the connection end of the coil windings will generate without change in connections, but the terminal phase sequence will be 1, 3, 2.

Synchronous condensers and synchronous motors may be operated with counterclockwise shaft rotation viewed from the connection end of the coil windings by connecting them to leads in which the phase sequence is 1, 2, 3, in the following manner:
a. Power leads................1, 2, 3
b. Machine terminals.......1, 3, 2
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ronaldrc said:
99 percent of all your single phase motor rotate CW looking at the motors output shaft:)
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That is in agreement with 2.24 I posted above

The standard direction of rotation for all alternating-current single-phase motors, all synchronous motors, and all universal motors shall be counterclockwise when facing the end of the machine opposite the drive end.
Click to expand...
 
taylorp said:
Kind of like which side of the road to drive on. (oops, that was a dumb example.)
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I think it is a good example. I went to our local bypass, four lanes of traffic, and stood in the middle and watched the traffic going from north to south and noticed that it was going from right to left.

I then turn around and watched the traffic that was going from south to north and low and behold it was going from right to left also.

This was enough proof to me that all four lanes of traffic were going in the same direction. Maybe this is true about electric motors and they are going both clock wise and counter clock wise at the same time depending on which end you are standing at.

I also got in my car and looked out the window at the left front wheel as I let it roll down the driveway and noticed that it was turning counter clock wise. I then let the wife drive as I looked out the window at the right wheel and it was turning clock wise. I am trying to figure out why that car don?t go around in circles.

Now don?t laugh as this is science at work! :slaphead:
 
jwelectric said:
I think it is a good example. I went to our local bypass, four lanes of traffic, and stood in the middle and watched the traffic going from north to south and noticed that it was going from right to left.

I then turn around and watched the traffic that was going from south to north and low and behold it was going from right to left also.

This was enough proof to me that all four lanes of traffic were going in the same direction. Maybe this is true about electric motors and they are going both clock wise and counter clock wise at the same time depending on which end you are standing at.

I also got in my car and looked out the window at the left front wheel as I let it roll down the driveway and noticed that it was turning counter clock wise. I then let the wife drive as I looked out the window at the right wheel and it was turning clock wise. I am trying to figure out why that car don?t go around in circles.

Now don?t laugh as this is science at work! :slaphead:
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Reminds me of an episode of "the Andy Griffith show" where Andy and Barney are facing each other and Andy pulls out a Buffalo nickel. He tells Barney it is a rare coin because it was minted/stamped wrong. Barney asked why that was. Andy tells him the Buffalo is pointing the wrong direction. He asks Barney to look at his own Buffalo nickel to see which way his is pointing. Barney looks at his and says it's pointing that way (to his left)
Andy says, see there, mine is pointing that way (Barney's right, facing Andy)

Barney says he doesn't believe that so Andy told him to come around the desk and look at his. He says, now which way is the Buffalo pointing on mine. Barney points the way Andy told him. Now which way was yours pointing? Barney points the way he pointed when on the other side of the desk.
Barney then wants to buy Andy's nickel!:lol:
 
Here is from the 2011 version:

2.24 DIRECTION OF ROTATION
The standard direction of rotation for all alternating-current single-phase generators, all synchronous
generators, and all universal generators shall be clockwise when facing the end of the machine opposite
the drive end.
The direction of rotation of a generator mounted as a part of an engine-generator set is usually
counterclockwise when facing the end opposite the drive end.
The standard direction of rotation for all alternating-current single-phase motors, all synchronous motors,
and all universal motors shall be counterclockwise when facing the end of the machine opposite the drive
end.
The standard direction of rotation for polyphase induction motors and generators, when only the terminal
markings U, V, W are used, in accordance with 2.60.1.2 and are connected to L1, L2, and L3 respectively
shall be counterclockwise when facing the end opposite the drive end, unless otherwise marked on the
machine. No direction of rotation is defined when terminal markings T1, T2, T3 are used, either alone or
in addition to the markings U, V, W.

I find that last note a bit interesting.
 
BPoindexter said:
... No direction of rotation is defined when terminal markings T1, T2, T3 are used, either alone or
in addition to the markings U, V, W.

I find that last note a bit interesting.
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Well at least an improvement from the 2003/2004 version where terminal markings had no correlation to rotation. Even with the "improvement", I'll still bump motors to verify rotation :p
 
Go back in time?

Go back in time?

From above: "The standard direction of rotation for all alternating-current single-phase motors, all synchronous motors,
and all universal motors shall be counterclockwise when facing the end of the machine opposite the drive
end."

-Whew, that was close. Because if the standard dictated that a clock's motor turn CCW looking from the drive end, (i.e ran backwards) that would seriously alter the universe's space-time continuum.
:D
 
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