written pole tewritten-pole-technology

WRITTEN-POLE ELECTRIC MOTORS

Presented by:Utkalika Sahoo (4th yr Electrical Engg.)

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CONTENTS

•INTRODUCTION•DIFFERENCES•LIMITATIONS OF CONVENTIONAL TECHNOLOGY•WRITTEN-POLE TECHNOLOGY•CONSTRUCTION•OPERATION•OPERATIONAL BENEFITS•ADVANTAGES•APPLICATIONS•RECOGNITIONS•CONCLUSION•REFERENCESWRITTEN POLE TECHNOLOGY

INTRODUCTION• In the 1990’s, a new concept was developed in electric motors called the Written Pole® electric motor• This new motor type dramatically reduces starting currents of single phase motors• The motor uses an innovative approach of controlling the magnetic field of the motor to reduce the starting current requirements• The result is a motor that has starting current requirements of only about twice the normal running current and, as an added benefit • The motors have efficiencies of 90% or better compared to conventional motors, which have efficiencies of around 85%

3WRITTEN POLE TECHNOLOGY

BASIC DIFFERENCES….

• Rotating field is developed.• In a convectional motor poles are fixed.• In a written pole motors a magnet layer is

written at different places on motor’s poles as the rotor turns.

• Written pole has much lower starting current than traditional motors prevents voltage dips etc….

• Slow start up speeds prevents water hammering.

LIMITATIONS OF CONVENTIONAL TECHNOLOGY

1.Dependence of speed on no. of poles of rotor

Speed = 120 X frequency no. of poles

2.The machine must have even no. of poles and deviating from this condition will cause unstability at its rated speed


AN INNOVATIVE PATENTED TECHNOLOGY

• In the 1990’s, with support from the EPRI, the Precise Power Corporation of Bradenton, Florida, developed a new concept in electric motors called the Written Pole® electric motor.


WRITTEN-POLE TECHNOLOGY

• The patented Written-Pole® Technology allows the magnetic pole pattern on the magnet layer to be changed to a desired pattern while the machine is rotating and therefore breaks the relationship between rotor speed and output frequency.


Contd…..

CONSTRUCTION


Contd…

• Written Pole motors use similar construction techniques found in conventional motors

• A continuous layer of ferrite magnets on the surface of the rotor, along with a high-density exciter winding contained within the stator winding

• The basic platform consists of a conventional steel shaft inserted into a lamination stack containing a high resistance rotor cage

Contd……


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• The high resistance cage is a key factor in limiting the starting current of Written-Pole motors

• The stator lamination stack is constructed using low loss electrical steel laminations

• The concentrated excitation windings are contained within the stator structure and are located between the main stator windings

Contd……

WRITTEN POLE TECHNOLOGY

Contd……

• The actual size and quantity of the poles generated on the surface of the rotor depends on the rotational speed of the machine.

• Lower speeds result in a large number of smaller poles with shorter spans while higher speed results in a smaller number of larger poles with longer spans.

Contd…..

Contd……

Contd…13WRITTEN POLE TECHNOLOGY

OPERATION

• A written-pole motor employs one of three modes of operation based on the rotational speed of the machine:

1. START MODE 2. TRANSITION MODE 3. RUN MODE


Start mode• In start mode a written pole produces a

large amount of hysteresis and induction torque which helps to accelerate the motor to its rated speed.

• W.P.T. technology is able to produce synchronous torque over a wide range providing gentler ramp which protects the load from mechanical damage.

• Lower starting current so lower temp. rise permitting high freq. starts and restarts.

Contd…….

Transition mode• As the written pole motor accelerates it

enters into transition mode during which the excitation voltage begins to influence the magnetic geometry of the rotor.

• Electrical synchronization is achieve before mechanical synchronization .

• Ability to start high inertia loads.

Run mode• Excitation not reqd., motor in normal mode.

Contd…….

OPERATIONAL BENEFITS

Feature Conventional WPSpeed 3,560rpm 3600 rpmEfficiency 85% 93%Power factor 90.5% 100%Full-load power 53kW 40kWFull-load torque 73.7 ft-lb 73 ft-lb

Starting torque 88 ft-lb 82 ft-lbFull-load current 219 amps 173 ampsLocked rotor current 1450 amps 312ampsCost (p.u.) 1.0 1.2


ADVANTAGES

1. Low starting current requirements2. Energy efficient operation3. Unity power factor operation4. Simple construction5. Low temperature rise6. High inertia starting7. Instantaneous restart capability8. Ride through characteristics9. Three-phase applications


• The Written-Pole motor is designed to operate in ambient temperatures ranging from 32ºF to 104ºF

• However, test results show that Written-Pole motors have reliably operated in temperatures ranging from 42ºF to 122ºF

• They may be operated safely in the open air if there is adequate protection from direct rain

• The motor base must be mounted on a raised concrete pad or steel frame to avoid exposure to standing water

Contd……


A WRITTEN POLE RIDE THROUGH MOTOR USED IN A FARM


APPLICATIONS

• In a family of single and three-phase motive power and power protection systems used by many customers including the US Weather Service, NASA, Federal Aviation Authority, US Air Force and many commercial and industrial customers.

• Agriculture purpose in rural areas.• Conveyor belt applications.• To run a 3-phase generator.• At oil well beam pump.


RECOGNTION

• A recipient of the R&D 100 Award in 1994, Written-Pole technology was recognized by R&D Magazine as one of that year's most technologically significant innovations

• The technology has also been recognized by numerous technical organizations including the Professional Society of Engineers in the United States


CONCLUSION

• The written-pole motor also has performance advantages over a conventional induction motor including low starting current, very high operating efficiency, and excellent power factor. This motor technology has the additional benefit of being able to ride through brief service interruptions on single-phase power lines. When compared to the total system costs, written pole motors are an attractive alternative to convention three-phase induction motors.


REFERENCES

• S.Hoffman, B.Banerjee and S.Samotyj “written-Pole-Revolution”. IEEE Power Eng. 6-9,1997

• A.Hannah,”Electrical field measurements on an EPRI two pole,20-hp .written pole motor.


THANK

YOU!

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