Hello all, I have a question about reversing fans, mainly how do they normally work. The fan I was looking at is 110 and the grainger book says that it includes a switch to run the fan in reverse, is this normally done via a low voltage signal cable or by changing windings in the fan motor. I understand that with three phase you can reverse two of the phases to run in reverse but I can't see how to reverse single phase. Thanks in advance.

Jim

Interchange leads 5&8 on the start winding.This will change the north pole position.I know this works on a split phase motor.Ive done it on other types as well but the only diagram ive seen was a split phase on page 347 of the IPT training manual by Herb Putts.Someone will correct me if Im wrong?

[This message has been edited by frank (edited 09-08-2003).]

[This message has been edited by frank (edited 09-08-2003).]

So on a fan with with a remote reversing switch there would be three wires going to it, all with 110 on them?

Going with Franks description

Six + Ground.

Four to run terminals 5 & 8 back and forth from the motor to the switch and two for power.

All the conductors would need to be line voltage.

Bob

JCooper,
This is a subject that has caused quite a bit of confusion to more than one apprentice, over the years.
It really depends on what sort of motor one is referring to.
Any Split-Phase motor can be reversed by reversing the polarity of either the Start orthe Run winding, but not both.
Shaded-pole motors cannot be reversed and these come in CW (clockwise) and CCW (counter-clockwise) versions.
You can reverse any Cage motor by reversing the polarity of the Phase-Neutral connections at the motor.

Jim,

Check out the drawings for 1 Phase Motors in the Technical Reference section.
(click on the blue "1 Phase Motors" text, or use the link below) https://www.electrical-contractor.net/ubb/Forum15/HTML/000031.html

This page describes several commonly used 1 Phase Induction Motors.

The first drawing - Fig. 1PM01 - shows the basic reversal connections consept that is typical for the Motors shown on that page.

Sorry we do not have exact terminal numbers to list with the schematics, but the drawings should be very helpful to you anyway.

Scott35

Most ceiling fans are shaded pole and they can be reversible.
The poles have two shading rings, one on each side of the core. Each has external connections to the switch. When the direction is changed one ring circuit is broken and the other is completed.

I disagree I understand shaded pole motors must be disasembled and flipped to reverse rotaton as Trumpy says it cant be rewired.Bathroom exaust fans are shaded pole and look like a"skullatin motor .Ceiling fans are generaly split phase.Shaded pole motors are clunky loud motors that last forever and are generaly too loud for use in rooms where you would try to sleep or hold a conversation.If i'm wrong someone will correct me and please do always learning here.Also ive only seen copper clips used to shade the pole and other then a bathroom i can only call seeing them in machines like ice makers ect

[This message has been edited by frank (edited 09-11-2003).]

[This message has been edited by frank (edited 09-11-2003).]

I may be wrong as well. I have never take one apart.
I was told this in school by a reliable instructor, but he admitted never taking one apart either.
Now that you have me curious, I will go down to the dump with a hammer, find out for myself, and report my findings.
If anyone wants me to mail them the 'remaining evidence' please send postage.

I always thought those cheap little motors found in those reversible window fans from K-Mart had two sets of coils (three speeds intake, three speeds exhaust). No?

I'm talking about the cheap exaust fans mounted in the bathroom ceiling that are vented with pipe.The motor is not enclosed and the shaded pole is achived by a little copper or brass plate(can't remember the type of metal)I The same idea as a shaded pole used on mechanical alternators for cycling condensate pumps.I think there are motors with shading poles but thought they aren't called shaded pole motors.Now I'm getting confused.I thought that the major reason for the shaded pole was to reduce magnetic flux and send the rotor in a given direction on start up.Am i confusing this with a compensating winding?Ok now have to go find out.

Found it."The shaded pole motor is an induction motor that utilizes a short circuited coil or copper ring called a shading coil to produce the starting torque.The shading pole is wound around one end of the stator pole face.
Current flowing in the primary stator windings will produce a magnetic field which induces a voltage into the shading coil and causes a high current to flow in the shaded pole coil.The magnetic field that is developed by the shaded pole current now opposes the magnetic field that initially created it.This shaded coil field is nearly 90 electrical degrees behinde the the main magnetic field and the interaction results in rotational torque.
The direction of rotation is determined by the shading coils with the motor turning toward the shaded pole.Reversing a shaded pole motor is very difficult.It involves either disassembling the motor and reversing the the stator end to end or moving the the shading coils".Page 350 of IPTs ELECTRICAL TRAINING MANUAL by Herb Puttz
Well not exactly what is thought but close enough i guess.A compensating winding is used i universal motors to reduce armature reaction,page 351.

[This message has been edited by frank (edited 09-12-2003).]

Frank,
That would have to be a cheap fan, indeed, if it were to use a Shaded pole motor!.
Normally these motors have next to no Torque and are really only for driving fans and other light loads, record players use them too!.

Trumpy,
yep it goes on to say that there is a low hp requirement 1/100hp to 1.5hp.Effciencies are 5% to 35% and operate at low power factors.Uses are small fans ,turn-tables clocks and valve operators.

There's quite a variety of 1Ø Motors.

The common Split Phase Induction Squirrel Cage Rotor type come in several flavors:
<OL TYPE=A>

[*] Split Phase-Resistance Start (no "compensation" in the Aux. Circuit,

[*] Split Phase-Capacitor Start (large value Capacitor in series with Aux. Circuit),

[*] Split Phase-Capacitor Start/Run (large Cap for starting, smaller Cap for running),

[*] Permanent Split (Phase) Capacitor-or "PSC" for short (Capacitor and Aux. Circuit always connected),

[*] Variations of the above for General Purpose, High-Torque and Two-Speed Pole Changing.
</OL>

Other Induction types include:
<OL TYPE=A>

[*] Shaded-Pole types (as previously discussed). These Motors do not have Starting Switches or Capacitors for the
Aux. Circuit, and the Aux. Circuit is always active in the operation via induction,

[*] Hysteresis Motors (typically used for Clocks and Phonographs). These are true Synchronous type AC Motors,

[*] Reluctance Motors - also Synchronous type Motors.
</OL>

1Ø AC Commutator "Universal" Motors include:
<OL TYPE=A>

[*] Series connected ("Simple Series"),

[*] Compensated Series connected,

[*] Repulsion Motors ("Simple" and "Armature-Excited"). These are Commutator type Motors with no external
connection to the Armature.

[*] Versions of the above with or without a speed Governor.
</OL>

And of course - DC Commutator Motors!

For the Repulsion Motors, the series AC circuit flows only thru the windings, not thru windings and armature.
The Armature is short circuited outside of the brushes. On the Armature-Excited type, there is a Variable Ratio Transformer in series with "½" of the Armature Circuit (it has 4 poles, or 4 brushes).

Variations of the Repulsion Motor are the Squirrel Cage Repulsion Motors. These "Brush-Shifting" Motors come in Series and Shunt wound arrangements, along with Single and Polyphase setups.

I would really like to add Schematics and description text for these types of Motors in the Technical Reference area.
Maybe sometime soon... maybe not

Scott35

--
This Message Was Sent From:
Scott E. Thompson / Thompson Electric
Via PC#5 (W/S P55C.LOC05.001)
E-Mail: adst@pacbell.net http://www.setelectric.electrical-contractor.net
Always Look For This "Sigfile" Or One Similar.
----------------------------------------------
Definitions:
Control (CON-TROL) n.;
A Very Small Prisoner That Lives Under A Bridge.
Asset (ASS-ETTE) n.;
A Little Donkey.
Ascot (ASS-COTT) n.;
A Little Bed For Donkeys.
Naval Destroyer (NAYEE-VULE DEE-STROIE-EER) n.;
A Hula-Hoop With A Nail In It.

Trivia Question:
Q: What Makes The Tower Of Pisa Lean?
A: It Never Eats.

<homersimpson>DOHH!!!</homersimpson>

I pasted the Sigfile too!!!
(the text below "Scott35").

Oh well, it might make some interresting discussions!

Scott35

Repulsion motors are not universal motors
(Universal, meaining they need not work on line frequinecy sinusoidal AC.) Repulsion motors need 60Hz to operate. FWIW, they reverse by moving the position of the brushes on the chassis.

Ceiling fans are split phase type, the reverse by switching the polarity of one winding in relation to the other.

I have schematics at http://www.hurontel.on.ca/~taitg/pages/cfan.html

BTW, the 1PM04b is incorrect. In the high voltage configuration, the start winding is usually in parallel with one of the run windings, usually the one opposite the protector.

classicsat;


Not sure what you mean here.
The Aux. Winding is in Parallel with one end of one Run Winding.

I drew this the same way we've been hooking them up for many years. Maybe we were doing them all wrong???

Just a little cornfused on your reply.

Scott35

In the diagram, the entire start circuit is directly across the 240V line. That circuit is 120V (or else the motor wouldn't work wired for 120V), an paralleled with one of the two run windings, which are 120V each.

I took the liberty to correct the image.
[img="http://www.hurontel.on.ca/~taitg/temp/22ovmotor.gif"]

Actually, the Capacitor / Winding Series Circuit will result in no more than 120 VAC across a given element, when the input Voltage is 240 VAC.

Notice the Voltage rating of the Start Capacitor - it is apx. 130 VAC.

It should be more of a curiousity for the Motor running with an input Voltage of ± 120 VAC, since the Start Circuit will have ± 60 VAC across the elements.

Scott35