References1. Chapter 11. Factional-Horsepower AC Motors, Electric Machinery, 3rd, A.E. Fitzgerald, Charles

Kingsley, JR., and Alexander Kusko, 1971, McGraw-Hill 2. Chapter 8. Single-Phase Induction Motors, Electrical Power and Controls, by Timothy L.

Skvarenina and William E. DeWitt, 2004, Prentice Hall 3. Industrial Electricity, 8th edition, by Michael Brumbach, published by Delmar Cenage Learning4. Electric Motors & Motor Controls, 2nd Edition, by Jeff Keljik, published by Delmar Cenage

Learning

• Horsepower = (Foot pounds torques) x (Revolution per minute)/5250•

○

○ The speed of the rotating magnetic field around the stator

Synchronous speed RPM, Ns = (Cycles per Minute)/ (Pair of Pole)

• Rotor: the rotating portion of the motor•

○ Slip = (Ns – Nr)/Ns x 100%Slip: the difference in speed between the Ns and rotor speed Nr

Single-Phase Motors

Principle of Operation

• No starting torque, but if started by auxiliary means it will continue to run.• With alternating current applied into the stator coils, the stator-MMF wave is stationary in space

but pulsates in magnitude, the stator-field strength alternating in polarity and varying sinusoidally with time.

• Rotor currents are induced by transformer action. These currents flow in such a direction as to produce an MMF opposing the stator MMF.

•

F1 = F1(peak) cosθIf the space wave of stator MMF F1 can be expressed as

•

F1(peak) = F1(max) cosωt, then F1 = F1(peak) cosθ = F1(max) cosωt cosθ, and finally F1 = ½ F1(max) cos(θ – ωt) + ½ F1(max) cos(θ + ωt)

If the stator current is a cosine function of time, the instantaneous value of the spatial peak of the pulsating MMF wave is

• The first wave, whose argument is (θ – ωt), travels in the forward direction of θ; the second wave, whose argument is (θ + ωt), travels in the backward direction of θ. So currents flow in such a direction as to produce an MMF (assume it is traveling with a backward rotating in –ω direction or counter clockwise) opposing the stator MMF (assume it is traveling with a forward rotating in +ω direction or clockwise).

• The axis of the rotor MMF wave coincides with that of the stator field, the torque angle therefore is zero, and no starting torque is produced.

• The motor is merely a single phase static transformer with a short-circuit secondary• If the motor were started by auxiliary means it would produce torque in whatever direction is

was startedUsing capacitors to produce phase shift•

An induction motor with a cage rotor and a single stator winding (distributed in slots) [1]

Lecture 14 - Single Phase MotorsMonday, July 28, 2014 4:05 PM

ECE 211 Lectures Page 1

• The motor is merely a single phase static transformer with a short-circuit secondary• If the motor were started by auxiliary means it would produce torque in whatever direction is

was startedUsing capacitors to produce phase shift•

• S# 316P 260• HP ¼• RPM 1725 … The RPM speed at rated horsepower

V 115 … Voltage at which the motor may be operated•

• A 5.1 … Normal current drawn at rated load, rated voltage, and rated frequency• HZ 60 … Frequency at which the motor is to be operated• FR A48 … Frame size as defined by NEMA (National Electrical Manufacturers Association)• TIME CONT … Duty rating, the period of time the motor may be operated without overheating

CONTINOUSLY•

○ A - automatic reset, U.L. (Underwriter’s Laboratories) approved

○ B - lock rotor only

○ M - manual rest, U.L. approved

○ T - automatic, not U.L. approved

○ J - manual reset, not U.L. approved

THERMALLY PROTECTED TYPE

• SER HF81 … Manufacturers Code Number• TYPE FH … Motor type letter code• SF 1.35 … Service factor is a multiplier applied to the rated horsepower. It indicates a

permissible horsepower loading that may be carried when the motor is operating at rated voltage and frequency

• PH1 … Type of power, single phase AC• SFA 5.7 … Service factor amps (current)• AMB 40 … Ambient maximum degrees centigrade• INS A … Insulation class

HSG OPEN … Housing or type of enclosure•

• Wiring diagram… etc.,

Name Plate Example, The AC’s and DCs of Electric Motors - Booklet, http://www.centuryelectricmotor.com/Motor-Mastery-University.aspx

• Split-phase induction motor (SPIM)Capacitor Start Induction Motor (CSIM)•

• Permanent Split-Capacitor Induction Motor (PSCIM)• Two Capacitor Motor• Shaded Pole Motor

Universal Motor•

Types of single-phase motors

Split-Phase Induction Motor

•

Main winding Auxiliary winding Centrifugal switch in the auxiliary circuitry that opens as the motor approaches full

speed

Construction:

• Relative low starting torque (100% - 150% of rated torque)

PumpsApplications•

ECE 211 Lectures Page 2

speed• Relative low starting torque (100% - 150% of rated torque)

Pumps Air Conditioning equipment Farm equipment Conveyors Business machines Gear reducers

Compressors

Tools

Fans and Blowers

Packaging equipment

Applications•

Source: Weg Electric Motors

Capacitor-Start Induction Motor (CSIM)

• Main winding• Auxiliary winding• A capacitor sized for starting, in series with the auxiliary winding • Centrifugal switch in the auxiliary circuits to remove the auxiliary winding after start-up

Construction

Permanent Split-Capacitor (PSC) motor

• Main winding• Auxiliary winding• A capacitor sized for running, in series with the auxiliary winding• Starting torque is very low (about 75% of rated torque)

Construction

ECE 211 Lectures Page 3

Grainer Blower Motor, PSC, 1/3 HP, 277V

Two-capacitor Motor

• Main winding• Auxiliary winding• A capacitor sized for starting, in series with the centrifugal switch• A capacitor sized for running• For large (10-15 HP) single-phase motor

Construction

Very small machine (0.05 HP) Not very efficient, but it is a simple, cheap, and rugged machine

o Stator iron is wrapped with several short-circuit turns of copper conductor (shading coil)

Construction of a shaded-pole motor and operation of a shading pole

Shaded-pole motor

A DC motor designed to run on AC Very high no-load speed that drops rapidly as the load increases Applications: portable drills, saws, routers, vacuum cleaners, etc Example of Universal Motor, http://www.youtube.com/watch?v=Crv4oGmtjL0

Universal motor

ECE 211 Lectures Page 4

Johnson Electric Universal Motor

Universal Motor Control Diagrams

Universal Motor Control diagram, Source: http://www.google.com/imgres?

imgurl=http://www.renesas.com/media/applications/key_technology/motor_control/motor_algorithms/child_folder/UniversalMotorContorl-TRIAC.gif&imgrefurl=http://www.renesas.com/applications/key_technology/motor_control/motor_algorithms/child/universal.jsp&h=371&w=547&sz=13&tbnid=UJ2uRrbbDQREBM:&tbnh=81&tbnw=120&prev=/search%3Fq%3DUniversal%2Bmotor%26tbm%3Disch%26tbo%3Du&zoom=1&q=Universal+motor&usg=__0yCbiVecREcZbCtbcC36QNO0JPQ=&docid=3n49OlLK8S1BoM&sa=X&ei=A8JsUYLWGciy2gX22YCwBQ&ved=0CEAQ9QEwAg&dur=115

Web Site ReferenceCentury Electric Motors – Regal Beloit America, Inc, http://www.centuryelectricmotor.com/Training & Tech InformationThe AC’s and DCs of Electric Motors - Booklet, http://www.centuryelectricmotor.com/Motor-Mastery-University.aspxJohnson Electric, http://www.johnsonelectric.com/en/products/motion/ac-motors/universal-motors.htmlGRAINGER PSC Motors, http://www.grainger.com/Grainger/ecatalog/N-1z0dugcWeg Single-Phase: NEMA 48 & 56 ODP Split Phase, http://www.weg.net/us/Products-Services/Electric-Motors/Fractional-Motors/Single-Phase-NEMA-48-56-ODP-Split-PhaseCSIR vs. CSCR, Franklin Electric, http://www.franklin-electric.com/media/documents/vol20no4.pdfTECO Induction Motor, TEFC NEMA Standards, http://www.teco.com.tw/fa/ecatalogue_file/en/AEEANE.pdfUnderstanding Induction Motor Nameplate Information, May 1, 2004, by Ed Cowen, P.E. Baldor Electric Co., http://ecmweb.com/mag/electric_understanding_induction_motor/ECN Electrical Forum, http://www.electrical-contractor.net/forums/ubbthreads.php/topics/178599/PSC_Motors_Schematics.htmlSingle-phase IMs, http://www.allaboutcircuits.com/vol_2/chpt_13/9.htmlMotor Control & Drives, http://www.infineon.com/cms/en/product/applications/Motor_Control_Drives/?ic=0501000

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