Power Saving System for Lathe

POWER SAVING SYSTEM FOR LATHE

POWER SAVING SYSTEM FOR LATHEABSTRACT In this modern world, the power saving system is help to us many purposes. Here we are using an electronic A.C motor speed regulator. This regulator is used to maintain the set speed of the motor constant.

The speed variation due to over load, line voltage fluctuations, over voltage, surge problems etc. Can be controlled and the speed is maintained constant by using this POWER SAVING SYSTEM IN LATHE. This unit can be used upto 1 H.P. A.C. motor.INTRODUCTION

In most of the applications of A.C. motor constant speed is most suitable for many applications. Speed varied due to overload, line voltage fluctuations in the input supply, over voltage, changes in the frequency. Surge problems etc., Hence to overcome the above electronics control unit are suggested. These problems may cause poor speed regulation of the motor and also lesser efficiency. To avoid these problems electronic this unit is used to maintain a constant speed of the motor.

Electronic Digital Speed control of A.C. Motor can be economically constructed ensuring the automatic speed regulation irrespective of load conditions however being essentially we can set the required constant speed with constant power. The motor speed can be from zero to maximum rated speed. This unit can be used upto 1HP A.C. Motor. For speed setting there is a regulating potentiometer with points for Indicating the setting we can select the required speed of the particular motor depends upon its purpose.

LATHEThe lathe is a machine tool used principally for shaping articles of metal (and sometimes wood or other materials) by causing the work piece to be held and rotated by the lathe while a tool bit is advanced into the work causing the cutting action. The basic lathe that was designed to cut cylindrical metal stock has been developed further to produce screw threads. tapered work. drilled holes. knurled surfaces, and crankshafts. The typical lathe provides a variety of rotating speeds and a means to manually and automatically move the cutting tool into the workpiece. Machinists and maintenance shop personnel must be thoroughly familiar with the lathe and its operations to accomplish the repair and fabrication of needed parts.

Lathes can be divided into three types for easy identification: engine lathes, turret lathes, and special purpose lathes. Small lathes can be bench mounted, are lightweight, and can be transported in wheeled vehicles easily. The larger lathes are floor mounted and may require special transportation if they must be moved. Field and maintenance shops generally use a lathe that can be adapted to many operations and that is not too large to be moved from one work site to another. The engine lathe (Figure 7-1 ) is ideally suited for this purpose. A trained operator can accomplish more machining jobs with the engine lathe than with any other machine tool. Turret lathes and special purpose lathes are usually used in production or job shops for mass production or specialized parts. while basic engine lathes are usually used for any type of lathe work. Further reference to lathes in this chapter will be about the various engine lathes.

SizesThe size of an engine lathe is determined by the largest piece of stock that can be machined. Before machining a workpiece, the following measurements must be considered: the diameter of the work that will swing over the bed and the length between lathe centers.

CategoriesSlight differences in the various engine lathes make it easy to group them into three categories: lightweight bench engine lathes, precision tool room lathes, and gap lathes, which are also known as extension- type lathes. These lathe categories are shown in Figure 7-2 Different manufacturers may use different lathe categories.

LightweightLightweight bench engine lathes are generally small lathes with a swing of 10 inches or less, mounted to a bench or table top. These lathes can accomplish most machining jobs, but may be limited due to the size of the material that can be turned.

PrecisionPrecision tool room lathes are also known as standard manufacturing lathes and are used for all lathe operations, such as turning, boring, drilling, reaming, producing screw threads, taper turning, knurling, and radius forming, and can be adapted for special milling operations with the appropriate fixture. This type of lathe can handle workplaces up to 25 inches in diameter and up to 200 inches long. However, the general size is about a 15-inch swing with 36 to 48 inches between centers. Many tool room lathes are used for special tool and die production due to the high accuracy of the machine.

GAP OR EXTENSION-TYPE LATHESGap or extension-type lathes are similar to toolroom lathes except that gap lathes can be adjusted to machine larger diameter and longer workplaces The operator can increase the swing by moving the bed a distance from the headstock, which is usually one or two feet. By sliding the bed away from the headstock, the gap lathe can be used to turn very long workplaces between centers.

LATHE COMPONENTSEngine lathes all have the same general functional parts, even though the specific location or shape of a certain part may differ from one manufacturer The bed is the foundation of the working parts of the lathe to another (Figure 7-3).

The main feature of its construction are the ways which are formed on its upper surface and run the full length of the bed Ways provide the means for holding the tailstock and carriage, which slide along the ways, in alignment with the permanently attached headstock

The headstock is located on the operators left end of the lathe bed. It contains the main spindle and oil reservoir and the gearing mechanism for obtaining various spindle speeds and for transmitting power to the feeding and threading mechanism. The headstock mechanism is driven by an electric motor connected either to a belt or pulley system or to a geared system. The main spindle is mounted on bearings in the headstock and is hardened and specially ground to fit different lathe holding devices. The spindle has a hole through its entire length to accommodate long workplaces. The hole in the nose of the spindle usually has a standard Morse taper which varies with the size of the lathe. Centers, collets, drill chucks, tapered shank drills and reamers may be inserted into the spindle. Chucks, drive plates, and faceplates may be screwed onto the spindle or clamped onto the spindle nose.

The tailstock is located on the opposite end of the lathe from the headstock. It supports one end of the work when machining between centers, supports long pieces held in the chuck, and holds various forms of cutting tools, such as drills, reamers, and taps. The tailstock is mounted on the ways and is designed to be clamped at any point along the ways. It has a sliding spindle that is operated by a hand wheel and clamped in position by means of a spindle clamp. The tailstock may be adjusted laterally (toward or away from the operator) by adjusting screws. It should be unclamped from the ways before any lateral adjustments are made, as this will allow the tailstock to be moved freely and prevent damage to the lateral adjustment screws.

The carriage includes the apron, saddle, compound rest, cross slide, tool post, and the cutting tool. It sits across the lathe ways and in front of the lathe bed. The function of the carriage is to carry and move the cutting tool. It can be moved by hand or by power and can be clamped into position with a locking nut. The saddle carries the cross slide and the compound rest. The cross slide is mounted on the dovetail ways on the top of the saddle and is moved back and forth at 90 to the axis of the lathe by the cross slide lead screw. The lead screw can be hand or power activated. A feed reversing lever, located on the carriage or headstock, can be used to cause the carriage and the cross slide to reverse the direction of travel. The compound rest is mounted on the cross slide and can be swiveled and clamped at any angle in a horizontal plane. The compound rest is used extensively in cutting steep tapers and angles for lathe centers. The cutting tool and tool holder are secured in the tool post which is mounted directly to the compound rest. The apron contains the gears and feed clutches which transmit motion from the feed rod or lead screw to the carriage and cross slide.

GENERAL LATHE OPERATIONS

LATHE SPEEDS, FEEDS, AND DEPTH OF CUTS

General operations on the lathe include straight and shoulder turning, facing, grooving, parting, turning tapers, and cutting various screw threads. Before these operations can be done, a thorough knowledge of the variable factors of lathe speeds, feeds, and depth of cut must be understood. These factors differ for each lathe operation, and failure to use these factors properly will result in machine failure or work damage. The kind of material being worked, the type of tool bit, the diameter and length of the workpiece, the type of cut desired (roughing or finishing), and the working condition of the lathe will determine which speed, feed, or depth of cut is best for any particular operation. The guidelines which follow for selecting speed, feed, and depth of cut are general in nature and may need to be changed as conditions dictate.

Cutting Speeds.The cutting speed of a tool bit is defined as the number of feet of workpiece surface, measured at the circumference, that passes the tool bit in one minute. The cutting speed, expressed in FPM, must not be confused with the spindle speed of the lathe which is expressed in RPM. To obtain uniform cutting speed, the lathe spindle must be revolved faster for workplaces of small diameter and slower for workplaces of large diameter. The proper cutting speed for a given job depends upon the hardness of the material being machined, the material of the tool bit, and how much feed and depth of cut is required. Cutting speeds for metal are usually expressed in surface feet per minute, measured on the circumference of the work. Spindle revolutions per minute (RPM) are determined by using the formula:

12 X SFM = RPM3.1416 X DWhich is simplified to:

4 X SFM = RPM

DWhere SFM is the rated surface feet per minute, also expressed as cutting speed.

RPM is the spindle speed in revolutions per minute

D is the diameter of the work in inches.

in order to use the formula simply insert the cutting speed of the metal and the diameter of the workpiece into the formula and you will have the RPM.

Turning a one-half inch piece of aluminum. cutting speed of 200 SFM. would result in the following:

4 x 200= 1600 RPM1/2Table 7-2 in Appendix A lists specific ranges of cutting speeds for turning and threading various materials under normal lathe conditions, using normal feeds and depth of cuts. Note that in Table 7-2 the measurement calculations are in inch and metric measures. The diameter measurements used in these calculations are the actual working diameters that are being machined. and not necessarily the largest diameter of the material. The cutting speeds have a wide range so that the lower end of the cutting speed range can be used for rough cutting and the higher end for finish cutting. If no cutting speed tables are available, remember that, generally. hard materials require a slower cutting speed than soft or ductile materials. Materials that are machined dry. without coolant. require a slower cutting speed than operations using coolant. Lathes that are worn and in poor condition will require slower speeds than machines that are in good shape. If carbide-tipped tool bits are being used, speeds can be increased two to three times the speed used for high-speed tool bits.

FeedFeed is the term applied to the distance the tool bit advances along the work for each revolution of the lathe spindle. Feed is measured in inches or millimeters per revolution, depending on the lathe used and the operators system of measurement. Table 7-3 in Appendix A is a guide that can be used to select feed for general roughing and finishing operations. A light feed must be used on slender and small workplaces to avoid damage. If an irregular finish or chatter marks develop while turning. reduce the feed and check the tool bit for alignment and sharpness. Regardless of how the work is held in the lathe, the tool should feed toward the headstock. This results in most of the pressure of the cut being put on the work holding device. If the cut must be fed toward the tailstock. use light feeds and light cuts to avoid pulling the workpiece loose.

MICROMETER COLLARGraduated micrometer collars can be used to accurately measure this tool bit movement to and away from the lathe center axis. Thus. the depth of cut can be accurately measured when moving the tool bit on the cross slide by using the cross slide micrometer collar. The compound rest is also equipped with a micrometer collar. These collars can measure in inches or in millimeters, or they can be equipped with a dual readout collar that has both. Some collars measure the exact tool bit movement. while others are designed to measure the amount of material removed from the workpiece (twice the tool bit movement). Consult the operators instruction manual for specific information on graduated collar use.

FACINGFacing is machining the ends and shoulders of a piece of stock smooth. flat, and perpendicular to the lathe axis. Facing is used to cut work to the desired length and to produce a surface from which accurate measurements may be taken.

H O W C A N I T S A V E E N E R G Y ?1) Smart ControlThis computerized control delivers high energy efficiency through precise control of the spindle.

\The spindle reports to the computer where it is and the computer compares this information with where the spindle is suppose to be. After the analysis, the computer will instantly adjust power drawn. This is all done instantaneously, you wouldnt be aware of this adjustment occurring. For example, at 2000rpm, the computerised DVR motor controller is calculating spindle position at 400 x a second, and minutely adjusting just as fast!

The DVR motor only draws as much power as it needs for each particular turning project and provides more or less power as needed to maintain the spindle in the correct speed. At low speed, almost no losses in the rotor are generated.

2) Less Heat GeneratedOrdinary DC and AC motors generate lots of heat in low speed or when under heavy load. This heat not only can burn out the wires but also wastes lots of energy needlessly.

DVR motor works by pure magnetic attraction. The motor can safely and efficiently work in very low speed and have high torque at the same time. This results in low heat generated and high component reliability.

3) Direct Drive SystemMany other lathes also achieve variable speed by using an electronic or mechanism device. However, you may not know that these conventionally driven lathes are losing up to 20% of energy through the lathe belt or gear system.

This means a 2 HP motor can only deliver 1.6HP energy to the lathe spindle. Sadly, you still need to pay your power bill for the 0.4HP energy lost in your variable speed device.

Because the DVR motor is a direct drive system, it can work efficiently in low speed and with heavy loads. There is no power loss through the belting system and this system also eliminates the vibration caused by the belt and pulleys.

Major Problems in Lathe

Metal working latheis an extremely useful piece of equipment that you can use in your workshop. For those who do extensive metal work, owning a metal working lathe is very important. However, having said that, it is also important to note that this piece of equipment is as dangerous as it is useful. It may increase the range of jobs that you can do, but it can also cause accidents. There are many different lathe problems that can occur while you are using this tool. Fortunately, most of these problems can be avoided.

1. Metal is not Cutting ProperlyThis usually happens when the cutting tool has not been set properly. Before you begin working, always check the cutting tool installed on the metal working lathe and make sure that it is placed right in the center. The proper positioning of the cutting tool is important to ensure that the cuts are made accurately. As you cut the metal, the tip of the cutting tool may become heated due to friction. Give the equipment frequent breaks so that the tools cool off and the chuck does not rotate at a speed that cannot be controlled.2. Metal Working Lathe Is Not Working Properly

The tailstock of the metal working lathe may not be fixed properly. Although the tailstock does not have any specific purpose, it has to be locked down properly before the chuck can be fed into the metal. If the tailstock remains loose, the metal may not be cut properly. To tighten the tailstock, inspect the screws closely, and if they are loose, tighten them properly.3. Carriage Is Not Moving

It is important to know how to move the carriage of the equipment. The carriage moves along its tracks. Moving the carriage is something that needs to be mastered in order for the machine to work efficiently. Along with the carriage, the power feed handles also have to be worked properly.

4. Threads Are Not Being Cut Properly

In a metal working lathe, the cutting of the threads is controlled by a dial. It is always easier to control the dial when you are working at a lower rpm. To be able to control the dial efficiently, test the dial at different speeds by using different kind of feeds. With each feed and speed, examine the ease of handling that you experience. This way, you can get a feel of working and controlling the dials before you actually begin using the machine on the metal.

5. Accidents

Metal working safety cannot be stressed enough. Safety is crucial whenever you are working any kind of machinery. Safety Goggles are a must if you want to protect your eyes. If you are wearing long sleeves while working, make sure that they are either buttoned or folded so that they dot no get caught in the equipment. The carriage needs to be cleaned regularly so that metal dust does not settle on it. Keep a brush at a handy distance so that you can brush off stray metal particles. These metal particles have a way of settling on your skin while working and may cause bruises and scratches.

Troubleshooting the Mini Lathe Variable Speed DriveThere are several common types of failure that occur on the mini lathe's variable speed drive. Find the symptoms your lathe exhibits, and follow the steps to diagnose the problem.

This document covers the following mini lathes: Grizzly Industrial model G8688

Harbor Freight (Central Machinery) model 33684 Micro-Mark MicroLux models 82500 and 82710

Homier Speedway model 03911 (current production, not the early Speedway with the SCR controller)

How It Should WorkFirst, lets start by describing the proper operation of the mini lathe.

1. Turn on the power. Either open the big red emergency switch or press the illuminated rocker switch so it is lit.

2. Turn the speed control knob to zero. On machines with an emergency switch, there is an interlock that prevents the motor from starting unless the knob has been turned to zero after the power is on. On all machines it is a good idea to always start from zero speed.

3. Put the direction switch in forward or reverse.

4. Turn the speed control knob clockwise to start the motor turning.

Motor Will Not Run at AllIf the motor will not run at all, make the following checks:

1. Check that there is power to the receptacle from which the lathe is powered.

2. Check the fuse on the control panel. The required fuse is a 5-amp, fast-acting 5 mm x 20 mm fuse. See Testing the fuse and fuse holder.

3. Check the fuse holder. They are prone to breaking.

4. Check the motor brushes to ensure that they are making good contact with the commutator. In general, this means checking that the caps that secure the brushes are tight.

5. Check all wire terminations inside the electrical box, especially the slip-on connectors.

6. Check the switches and potentiometer for signs of physical failure. Test them as described below. See Component Tests.

7. Check the MOSFETs on the speed control board. See Testing a MOSFET in circuit.

8. Check the leads on the large power resistor near the center of the speed control board to ensure that a lead has not broken. If you find a broken lead, repair it with solder. Brace the resistor by placing a small blob of RTV silicone under it.

Motor Runs Only at Full SpeedIf the motor runs at full speed no matter the position of the speed control knob, one or both MOSFETs on the speed control board have failed in a shorted condition. See Testing a MOSFET in circuit.

Replace both MOSFETs. They are in parallel and must be matched (that is, the same part number from the same manufacturer) or one will take the entire load and fail prematurely.

Motor Runs IrregularlyIf the motor runs irregularly or makes arcing or popping noises, it might be a failure of a brush connection.

Remove the caps that retain the motor brushes and inspect the brushes to ensure that the braided copper wire connects the carbon brush to the brass contact cap. Repair or replace failed brushes.

Fuse Blows When Power Is Turned On1. Check all wire terminations inside the electrical box, especially the slip-on connectors.

2. Check the switches and potentiometer for signs of physical failure. See Component Tests.

3. Check the MOSFETs on the speed control board. See Testing a MOSFET in circuit.

Component TestsFollowing are specific tests for some components of the variable speed drive system. These procedures assume that you have and know how to use a volt/ohm/milliampmeter.

Testing the fuse and fuse holder Testing the emergency stop switch Testing the illuminated on-off switchTesting the speed control potentiometer Testing the forward/off/reverse switch Testing a MOSFET in circuitTo test the components you have to unscrew the four Philips head screws that retain the control box. Do not disconnect any of the wires, unless you need to for a particular test. With the control box loose, you can work inside it to test the components.

Testing the fuse and fuse holder

1. Unplug the power cord.

2. Remove the fuse from the fuse holder.

3. Check continuity between the two metal ends of the fuse. There should be continuity.

4. Inspect the fuse holder for cracks or breakage.

5. Replace the fuse in the fuse holder.

6. Check continuity between the two terminals on the fuse holder. There should be continuity.

Testing the emergency stop switch

1. Unplug the power cord.

2. Orient the switch so that the hinge is horizontal at the top and the cover swings up and down.

3. Raise the cover.

4. Check continuity between the two top terminals. There should be continuity between these terminals.

5. Check continuity between the two bottom terminals. There should be continuity between these terminals.

6. Close and latch the cover.

7. Check continuity between the two top terminals. There should be no continuity between these terminals.

8. Check continuity between the two bottom terminals. There should be no continuity between these terminals.

These tests are summarized in the table below:

TerminalsCover OpenCover Closed

Top terminalsConnectionNo connection

Bottom terminalsConnectionNo connection

Testing the illuminated on-off switch

1. Unplug the power cord.

2. Place the switch in the off position, as shown above.

3. Check continuity between the terminal on the 0 end and the other two terminals. There should be no continuity between any of the terminals.

4. Check continuity between the terminal on the 1 end and the other two terminals. There should be no continuity between any of the terminals.

5. Place the switch in the on position, with the 1 end depressed.

6. Check continuity between the terminal on the 0 end and the center terminal. There should be continuity.

7. Check continuity between the terminal on the 0 end and the far terminal. There should be no continuity.

8. Check continuity between the terminal on the 1 end and the other two terminals. There should be no continuity between any of the terminals.

These tests are summarized in the table below:

TerminalsSwitch OffSwitch On

0 to CenterNo connectionConnection

0 to 1No connectionNo connection

1 to CenterNo connectionNo connection

Testing the speed control potentiometer

There are two versions of the speed control potentiometer. Some have a switch on the back (and have five terminals), and some dont (and have three terminals).

1. Unplug the power cord.

2. If there are five terminals, turn the potentiometer shaft all the way counterclockwise.

3. If there are five terminals, check continuity between the two terminals on the back of the potentiometer. There should be continuity.

4. If there are five terminals, turn the potentiometer shaft clockwise about 10 or 15 degrees. You should hear a click as the switch changes position. Check continuitybetween the two terminals on the back of the potentiometer.

There should be no continuity.5. Measure the resistance between the two outside terminals on the side of the potentiometer. The resistance should be between 3000 and 5000 ohms.

6. Measure the resistance between the center terminal and one of the outside terminals on the side of the potentiometer. The resistance should change smoothly from near the value you measured in step 5 to near zero ohms as you turn the potentiometer shaft from one stop to the other.

7. Measure the resistance between the center terminal and the other outside terminal on the side of the potentiometer. The resistance should change smoothly (but in the opposite direction from step 6) from near zero ohms to near the value you measured in step 5 as you turn the potentiometer shaft from one stop to the other.

These tests are summarized in the table below:

TerminalsCounterclockwiseRotatingClockwise

Limitlimit

SwitchConnectionNo connectionNo

connection

Outer potentiometer3-5K ohms3-5K ohms3-5K ohms

terminals

Left to Center0 ohmsVaries from 0 to3-5K ohms

potentiometer terminals3-5K ohms

Right to Center3-5K ohmsVaries from 3-5K0 ohms

potentiometer terminalsto 0 ohms

Testing the forward/off/reverse switch

There are several versions of the forward/off/reverse switch. Some have six terminals, some have nine and some have twelve terminals. The testing procedure is the same for all of them.

1. Unplug the power cord.

2. Looking at the terminal side of the switch, rotate it so that the handle moves up and down. There are vertical columns of three terminals.

3. Place the switch in the off (center) position.

4. In each column of terminals, check continuity between the center terminal and the other two terminals. There should be no continuity between any of the terminals.

5. In each column of terminals, check continuity between the top terminal and the bottom terminal. There should be no continuity between these terminals.

6. Move the handle so it is in the up position.

7. In each column of terminals, check continuity between the center terminal and the bottom terminal. In all the columns there should be continuity between the center and the bottom terminal.

8. In each column of terminals, check continuity between the center terminal and the top terminal. In all the columns there should be no continuity between the center and the top terminal.

9. In each column of terminals, check continuity between the top terminal and the bottom terminal. There should be no continuity between these terminals.

10. Move the handle so it is in the down position.

11. In each column of terminals, check continuity between the center terminal and the top terminal. In all the columns there should be continuity between the center and the top terminal.

12. In each column of terminals, check continuity between the center terminal and the bottom terminal. In all the columns there should be no continuity between the center and the bottom terminal.

13. In each column of terminals, check continuity between the top terminal and the bottom terminal. There should be no continuity between these terminals.

These tests are summarized for each column of terminals in the table below:

TerminalsSwitch OffSwitch UpSwitch Down

Center to TopNo connectionNo connectionConnection

Center to BottomNo connectionConnectionNo connection

Top to BottomNo connectionNo connectionNo connection

Testing a MOSFET in circuitMOSFETs are very sensitive to static electricity. Here are the procedures the U. S. Navy recommends when testing them (out of circuit).

You must be extremely careful when working with MOSFETs because of their high degree of sensitivity to static voltages. As previously mentioned in this chapter, the soldering iron should be grounded. A metal plate should be placed on the workbench and grounded to the ship's hull through a 250-kilohm to 1 -megohm resistor. You should also wear a bracelet with an attached ground strap and ground yourself to the ship's hull through a 250-kilohm to 1-megohm resistor. You should not allow a MOSFET to come into contact with your clothing, plastics, or cellophane-type materials. A vacuum plunger (solder sucker) must not be used because of the high electrostatic charges it can generate. Solder removal by wicking is recommended. It is also good practice to wrap MOSFETs in metal foil when they are out of a circuit. To ensure MOSFET safety under test, use a portable volt-ohm-milliammeter (vom) to make MOSFET resistance measurements. A vtvm must never be used in testing

MOSFETs.

While you can follow most of these recommendations in your home shop (substituting a good ground for the ships hull), in our experience you shouldnt have much trouble while testing them in circuit if you just use a little common sense (dont pat your cat while making these tests).

If the measurement between any two pins is 0 ohms, the MOSFET has failed.

Pin 1 Pin 3

1. Set the VOM to the 200K Ohms scale. If your VOM does not have a 200K ohms scale, set it to the nearest scale to 200K ohms.

2. Confirm that the red lead is in the red connector on the VOM and that the black lead is in the black connector.

3. With the red probe on the lower numbered pin, measure the resistance from pin 1 to pin 3. The reading should be about 50K ohms.

4. With the red probe on the lower numbered pin, measure the resistance from pin 1 to pin 2. The reading should show infinity.

5. With the red probe on the lower numbered pin, measure the resistance from pin 2 to pin 3. The reading should show infinity.

6. With the black probe on the lower numbered pin, measure the resistance from pin 1 to pin 3. The reading should be about 50K ohms.

7. With the black probe on the lower numbered pin, measure the resistance from pin 1 to pin 2. The reading should show infinity.

8. With the black probe on the lower numbered pin, measure the resistance from pin 2 to pin 3. The reading should be about 120K to 140K ohms.

These tests are summarized in the table below:

Between PinsRed on lower numbered pinBlack on lower numbered pin

1350K ohms*50K ohms*

12Infinity ohmsInfinity ohms

23Infinity ohms120K-140K ohms

*The 50K ohms readings between pins 1 and 3 are measuring resistance on the circuit board. This same measurement with the MOSFET out of the circuit will indicate infinity

CIRCUIT OPERATION

The control circuit is consisting of an error amplifier speed amplifier, a current amplifier, voltage controlled oscillator, a trigger circuit and a full wave bridge converter.

The A.C motor is powered by an A.C converter, depending upon the firing angle of the SCR. The current supplied by the SCR will be lagging with the applied voltage, so speed control can be achieve by the varying the firing angle of the SCR.

The speed and current amplifier provided with regulated constant D.C. voltage. When the speed is set to a value by means of potentiometer, the error amplifier gives a voltage. The output from the error amplifier is amplified by a speed amplifier; the output from the speed amplifier drives a current amplifier. The output of the current amplifier provides a D.C voltage to the oscillator circuit depending on the amplifier of the input voltage available at the VCO.

BLOCK DIAGRAM

1- PHASE A.C. IN

APPLICATIONS

Industrial application Machinery Application Power Generation station Power Transmition StationADVANTAGES

Speed control upto 1 H.P A.C motor

Speed variation is smoothly.

This circuit is a Closed loop control system

In this circuit Isolation transformer is used so that the A.C motor is products

SCR firing angle is varied automatically

By slight modification of this circuit, the single phase induction motor speed also varied.

DISADVANTAGES

This circuit produce the sinusoidal A.C voltage only, not the pure A.C voltage The noise produced by the motor is high due to voltage variation The efficiency of the motor is decreased due to input voltage is varied by the SCR circuit.ConclusionThus the power saving system has been designed and it is verified experimentally. This system will save the electrical power used for the lathe system almost 20%.This is an simply and economically beneficial design and can be used for all small and large scale industry. Further work has been continued in the future to rectify the limitation.

CONTROLLED

RECTIFIER

AC/DC

CONVERTER

M

TRIGER

CIRCUIT

VCO

ERROR

AMPLIFIER

FEED BACK

AMPLIFIER

AMPLIFIER

CURRENT