E 2 Motors and Motor Starting 1 Fan

Basic Electric Motor • Stator – Stationary electromagnet • Rotor – Rotating magnet •

Exploded View of Motor STATOR (with windings) ROTOR (with shaft) © 2005 Refrigeration Training

Two-pole stator motor Stator Rotor (Stationary) (Rotates) Polarity reverses (N to S) on stator

Second half of cycle + _ S N Stator continues motion by repelling and

Motor Starting All motors need a phase shift to start rotation © 2005 Refrigeration

Motor Tries to Start Stator Equal and opposite attraction N S Rotor Equal and

A Phase Shift is Needed Stator N A phase shift causes rotation S Rotor

Shaded-Pole Motors • Low starting torque • Low efficiency • Low cost © 2005

Examples of Shaded-Pole Motors © 2005 Refrigeration Training Services - E 2#1 Fan Motors

Starting a Shaded-Pole Motor • Each pole has a copper band attached – The

Rotation toward the Shaded Pole N S N © 2005 Refrigeration Training Services -

Shaded-Pole Motor Wiring BLACK GREEN © 2005 Refrigeration Training Services - E 2#1 Fan

Changing Motor Rotation • Shaded-pole motors can be reversed: – First, turn stator around

Interesting Motor Fact Motor efficiency: A 100 watt 50% efficient motor will put out

Shaded-pole © 2005 Refrigeration Training Services - E 2#1 Fan Motors v 1. 1

To Reverse Rotation Turn Stator Around ` ` © 2005 Refrigeration Training Services -

Rotation is now reversed Turn fan blade around ` © 2005 Refrigeration Training Services

Multi-speed Shaded-Pole Motors • Speed depends on winding resistance – Low speed: most resistance

Shaded-Pole 3 -Speed Motor Wiring Common Wire is White (115 v) or Black (230

Split Phase Motors • Have two separate windings, a run and a start •

A Split Phase Motor is a Two-pole stator motor … with Start Windings added

Start & Run Winding Resistances W IN N DI RU NG C ST AR

Windings of a split phase motor © 2005 Refrigeration Training Services - E 2#1

Split Phase Motor This motor needs power to the start winding to start C

Fan Motor with Centrifugal Switch • A mechanical switch is used to de-energize the

Split Phase Motor with Centrifugal Switch Centrifugal switch opens start winding C S START

Fan Motor with Centrifugal Switch • The next slide is a picture of a

Motor with Centrifugal Switch Start winding energized Motor Speed Increases Weights shift, disk moves

Permanent Split Capacitor Motors • A run capacitor is “permanently” wired into the start

PSC Motor with run capacitor Low Starting Torque Low to Medium Cost Medium Efficiency

Split Phase Motor + Run Cap = PSC Motor DI IN W T NG

Interesting Motor Fact A PSC motor with a bad run capacitor will act like

PSC Motor Wiring Diagram BLACK LINE BROWN CAPACITOR GREEN © 2005 Refrigeration Training Services

Motor Speeds • The synchronous, or “nominal” speed of a motor can be determined

Two Pole Motor Windings Courtesy of Copeland 7200 2 = 3600 RPM © 2005

Calculating Motor Speeds • One cycle has two current flow reversals • 60 cycles

Four Pole Motor 1 1 2 2 4 7200 4 = 1800 RPM 4

Actual Motor Speed • Slippage is the loss of speed from motor load •

Multi-Speed Split Phase Motors • Actually they are “Multi-horsepower” • The windings are tapped

Single-Speed PSC Motor DI IN W ST NG DI IN T W AR N

Single-Speed PSC Motor DI T AR ST NG DI IN W IN N W

Multi-speed PSC Motor High Speed RH DI IN W AR T NG DI IN

3 -Speed PSC Motor Wiring Diagram BLACK-HIGH BLUE-MED LINE RED-LOW BROWN GREEN © 2005

Interesting Motor Fact • Multi-speed motors must be under a load to change speeds

PSC 3 -speed Motor Leads for changing motor rotation Run Capacitor Leads Common Wire

Three Phase Motors • High starting torque • High efficiency • Medium to high

Three Phase Motors © 2005 Refrigeration Training Services - E 2#1 Fan Motors v

Three Phase Motor Starting • No start windings or capacitors needed • High torque

3Ø Motor – Wye Connections L 1 T 1 208 V T 3 T

3Ø Motor – Delta Connections T 1 L 1 240 V T 3 T

Describing Common Motors • Motor descriptions include the following information: – Type – Enclosure

Common Motor Types © 2005 Refrigeration Training Services - E 2#1 Fan Motors v

Motor Enclosure Types • • Open Dripproof Totally enclosed fan cooled © 2005 Refrigeration

Open Enclosure Types Totally Open Dripproof Note: Prevents direct entry of moisture Clean and

Enclosed Type Motors Totally Enclosed Air Over Cooling from system air passing over the

Motor Mounting • Some of the more common mounts: – Rigid – Cradle –

Cradle Mount © 2005 Refrigeration Training Services - E 2#1 Fan Motors v 1.

Rigid Mount Motor housing is welded to the base © 2005 Refrigeration Training Services

Belly Band Mounting Motor slides into ring. Then band is tightened © 2005 Refrigeration

Stud Mounts Studs are bolted to fan guard or housing. © 2005 Refrigeration Training

Other Motor Mounting Styles C-frame © 2005 Refrigeration Training Services - E 2#1 Fan

Motor Nameplate • Nameplates contain essential information © 2005 Refrigeration Training Services - E

Motor Nameplate explained © 2005 Refrigeration Training Services - E 2#1 Fan Motors v

Motor Nameplate wiring diagram © 2005 Refrigeration Training Services - E 2#1 Fan Motors

Interesting Motor Facts • An overloaded motor (too small for the job): – Lower

© 2005 Refrigeration Training Services - E 2#1 Fan Motors v 1. 1 67

Slides: 67

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Basic Electric Motor • Stator – Stationary electromagnet • Rotor – Rotating magnet • Movement of the rotor – Rotates by repulsion and attraction of stator © 2005 Refrigeration Training Services - E 2#1 Fan Motors v 1. 1 2

Two-pole stator motor Stator Rotor (Stationary) (Rotates) Polarity reverses (N to S) on stator N S +_ N S Stator repels & attracts rotor into motion When stator is energized the rotor will make a half turn with each half of current cycle © 2005 Refrigeration Training Services - E 2#1 Fan Motors v 1. 1 4

Second half of cycle + _ S N Stator continues motion by repelling and attracting S N Polarity reverses (N to S) on stator The alternating current now changes direction © 2005 Refrigeration Training Services - E 2#1 Fan Motors v 1. 1 5

Motor Tries to Start Stator Equal and opposite attraction N S Rotor Equal and opposite attraction Power applied to stators Opposite attraction Rotor will NOT move N S Stator © 2005 Refrigeration Training Services - E 2#1 Fan Motors v 1. 1 7

A Phase Shift is Needed Stator N A phase shift causes rotation S Rotor N This phase shift can be caused by: üA shaded pole üA start winding üA capacitor ü 3 separate phases A magnetic field is formed at a slightly different angle S Stator © 2005 Refrigeration Training Services - E 2#1 Fan Motors v 1. 1 8

Starting a Shaded-Pole Motor • Each pole has a copper band attached – The shaded-pole provides the phase shift needed to start rotation • Usually impedance protected – A stalled blade will not cause burned windings © 2005 Refrigeration Training Services - E 2#1 Fan Motors v 1. 1 11

Multi-speed Shaded-Pole Motors • Speed depends on winding resistance – Low speed: most resistance – High speed: least resistance • Motor speed is based on where power is connected into the winding Common High Speed Medium Speed © 2005 Refrigeration Training Services - E 2#1 Fan Motors v 1. 1 Low Speed 19

Split Phase Motors • Have two separate windings, a run and a start • The start winding provides the phase shift for starting • More efficient and have more torque than shaded pole motors © 2005 Refrigeration Training Services - E 2#1 Fan Motors v 1. 1 21

Split Phase Motor This motor needs power to the start winding to start C S START WINDING This motor needs a start winding for a phase shift R RUN WINDING This motor needs power to the run winding to run LINE © 2005 Refrigeration Training Services - E 2#1 Fan Motors v 1. 1 25

Fan Motor with Centrifugal Switch • A mechanical switch is used to de-energize the start winding • The switch is attached to the motor shaft • After the motor starts, centrifugal force opens the switch • The start winding circuit remains open as long as the motor is running © 2005 Refrigeration Training Services - E 2#1 Fan Motors v 1. 1 26

Fan Motor with Centrifugal Switch • The next slide is a picture of a fan motor with the motor cover removed • The centrifugal switch is attached to the motor shaft • The switch contacts are attached to the end bell (motor cover) © 2005 Refrigeration Training Services - E 2#1 Fan Motors v 1. 1 28

Motor with Centrifugal Switch Start winding energized Motor Speed Increases Weights shift, disk moves back Before starting, disk pushes bar, closing contacts Contacts Open From Run Winding © 2005 Refrigeration Training Services - E 2#1 Fan Motors v 1. 1 To Start Winding Centrifugal Disk Switch 29

Permanent Split Capacitor Motors • A run capacitor is “permanently” wired into the start winding circuit • The capacitor provides partial voltage to the start winding, during start and run © 2005 Refrigeration Training Services - E 2#1 Fan Motors v 1. 1 30

Motor Speeds • The synchronous, or “nominal” speed of a motor can be determined by the number of its poles • The more poles, the lower the speed © 2005 Refrigeration Training Services - E 2#1 Fan Motors v 1. 1 35

Calculating Motor Speeds • One cycle has two current flow reversals • 60 cycles has 120 flow reversals • Speed = (60 Hz x 120 reversals) ÷ Poles Example: 7200 ÷ 2 Motor poles = 3600 RPM © 2005 Refrigeration Training Services - E 2#1 Fan Motors v 1. 1 37

Actual Motor Speed • Slippage is the loss of speed from motor load • The actual speed is less than the calculated speed Common motor speeds: Calculated: Actual: 2 Pole motor: 3600 3450 4 Pole motor: 1800 1750 6 Pole motor: 1200 1050 8 Pole motor: 900 850 © 2005 Refrigeration Training Services - E 2#1 Fan Motors v 1. 1 39

Multi-Speed Split Phase Motors • Actually they are “Multi-horsepower” • The windings are tapped so the motor is weaker, running slower under load • Example of a 3 -speed 1/3 HP motor: – High speed is 1/3 HP – Medium speed is 1/4 HP – Low speed is 1/6 HP © 2005 Refrigeration Training Services - E 2#1 Fan Motors v 1. 1 40

Interesting Motor Fact • Multi-speed motors must be under a load to change speeds – Example: A multi-speed blower removed from the blower compartment will run at high speed, no matter which speed tap is used © 2005 Refrigeration Training Services - E 2#1 Fan Motors v 1. 1 45

PSC 3 -speed Motor Leads for changing motor rotation Run Capacitor Leads Common Wire Low Speed (red) Medium Speed (blue) High Speed (black) © 2005 Refrigeration Training Services - E 2#1 Fan Motors v 1. 1 46

Open Enclosure Types Totally Open Dripproof Note: Prevents direct entry of moisture Clean and Mostly Dry Locations Clean and Dry Locations © 2005 Refrigeration Training Services - E 2#1 Fan Motors v 1. 1 55

Enclosed Type Motors Totally Enclosed Air Over Cooling from system air passing over the motor body Totally Enclosed Fan Cooled Cooling from fan forced air passing over the motor body Totally Enclosed are good for wet and dirty conditions © 2005 Refrigeration Training Services - E 2#1 Fan Motors v 1. 1 56

Interesting Motor Facts • An overloaded motor (too small for the job): – Lower speed, amperage above 10% of RLA, and overheating • An under-loaded motor (too big for the job): – Little change in speed, amperage 25% below RLA, and overheating © 2005 Refrigeration Training Services - E 2#1 Fan Motors v 1. 1 66