Transformer Seminar - Buck-Boost
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Buck-boost transformers can increase or decrease voltage within a range of 5-20%. They start as isolation transformers with outputs of 12-48V, but get connected as auto-transformers during installation, eliminating isolation. This allows them to boost or buck voltage using a smaller package than standard isolation transformers. Selection involves choosing the appropriate transformer based on system phase, frequency, line voltage, load voltage, and load KVA/amps using charts in the catalog. Low voltage can negatively impact motor operation through increased current, temperature rises, and reduced torque. Buck-boost transformers are useful for applications like air conditioners, motors, and tanning beds where minor voltage adjustments are needed.
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Transformer Seminar - Buck-Boost
- 1. Acme Electric Transformer Seminar Buck Boost Transformers
- 2. WHAT ARE BUCK-BOOST TRANSFORMERS? BUCK-BOOST TRANSFORMERS START OUT AS ISOLATION TRANSFORMERS WITH OUTPUTS FROM 12 TO 48 VOLTS, WHICH GET FIELD CONNECTED AS “AUTO” TRANSFORMERS TO INCREASE OR DECREASE VOLTAGE WITHIN A RANGE OF 5 TO 20 PERCENT. (ie, 208 T0 230 V) THEY DO NOT PROVIDE ISOLATION FROM THE SUPPLY BECAUSE THEY ARE “AUTO” CONNECTED DURING INSTALLATION!
- 4. BASIC PRINCIPLE CURRENT WILL FOLLOW PATH OF LEAST RESISTANCE
- 5. PRIMARY & SECONDARY HAVE THE SAME CAPACITY
- 7. AUTO CONNECTION INCREASES KVA CAPACITY
- 8. DATA NEEDED TO SELECT BUCK- BOOST TRANSFORMER 1. SYSTEM PHASE 2. SYSTEM FREQUENCY 3. LINE VOLTAGE 4. LOAD VOLTAGE 5. LOAD KVA, AMPS, OR HORSEPOWER (Available line voltage should be measured whenever possible)
- 9. SELECTION EXAMPLE #1 1. 1-PHASE 2. 60 HZ 3. LINE - 189 VOLTS 4. LOAD - 208 VOLTS 5. LOAD - 4 KVA
- 10. 1-PHASE 120 X 240 – 12/24 CHART REFER TO 1-PHASE SELECTION CHART IN SECTION 8 OF THE CATALOG ON PAGE 121
- 12. SELECTION EXAMPLE # 2 1. 1 - PHASE 2. 60 HZ 3. LINE - 208 VOLTS 4. LOAD - 240 VOLTS 5. LOAD - 60 AMPS
- 13. 1-PHASE 120 X 240 – 16/32 CHART REFER TO 1-PHASE SELECTION CHART IN SECTION 8 OF THE CATALOG ON PAGE 122
- 15. SELECTION EXAMPLE # 3 1. 1 - PHASE 2. 60 HZ 3. LINE - 240 VOLTS 4. LOAD - 208 VOLTS 5. LOAD - 14 KVA
- 16. 1-PHASE 120 X 240 – 16/32 CHART REFER TO 1-PHASE SELECTION CHART IN SECTION 8 OF THE CATALOG ON PAGE 122
- 18. SELECTION EXAMPLE # 4 1. 3 - PHASE 2. 60 HZ 3. LINE - 208 VOLTS 4. LOAD - 230 VOLTS 5. LOAD - 80 KVA
- 19. 3-PHASE 120 X 240 – 16/32 CHART REFER TO 3-PHASE CHART IN SECTION 8 OF THE CATALOG ON PAGE 125
- 21. TYPICAL APPLICATIONS FOR BUCK-BOOST TRANSFORMERS 1. AIR CONDITIONERS 2. AC MOTORS 3. PUMPS 4. TANNING BEDS (No. 1 application) 5. CONTROL CIRCUITS
- 22. GENERAL APPLICATION COMPARISON STANDARD ISOLATION TRANSFORMER • Handle large increases or decreases in voltage • Provide electrical isolation and shielding if required BUCK-BOOST TRANSFORMERS • Handle small increases or decreases in voltage (+/- 5 to 20%) • Do not provide electrical isolation (because they get “auto” connected)
- 23. EFFECTS OF LOW VOLTAGE ON MOTOR OPERATION VOLTAGE CURRENT TEMPERATURE - 5 % + 5 % + 11 % - 10 % + 11 % + 23 % - 15 % + 17 % + 38 %
- 24. EFFECTS OF LOW VOLTAGE ON MOTOR OPERATION • DETERIORATE INSULATION • NUISANCE TRIPPING OF BREAKERS • INSUFFICIENT MOTOR TORQUE • WASTED ENERGY AND MONEY
- 25. EFFECTS OF LOW VOLTAGE ON MOTOR TORQUE % RATED VOLTS % RATED TORQUE 100% 100% 90% 81% 80% 64%
- 26. CAUSES OF VOLTAGE MISMATCH • SERVICE VOLTAGE CHANGED AFTER EQUIPMENT INSTALLED • VOLTAGE DROP IN POWER LINE • ERRORS IN ORDERING EQUIPMENT • UTILITY CUTBACK IN SOURCE VOLTAGE
- 27. GENERAL SIZE COMPARISON STANDARD ISOLATION TRANSFORMER • 16”H X 14”W X 11”D 125 LBS • 1O KVA RATING BUCK-BOOST TRANSFORMER • 10”H X 6”W X 5”D 24 LBS • 1 KVA RATING
- 28. ACME BUCK-BOOST FEATURES • UL LISTED/CSA CERTIFIED • UL 3R ENCLOSURES • ALLOWABLE UNDER NEC • EPOXY ENCAPSULATED (EXCEPT 50, 100, 150 VA) • BROAD RANGE OF VOLTAGES • TEN YEAR WARRANTY
- 29. BUCK BOOST HANDS-ON LAB In this exercise we will wire a typical Buck- Boost transformer for the following applications: Input Output Diagram Connection Type 120V 12V K Isolation 120V 24V L Isolation 240V 12V M Isolation 240V 24V N Isolation 120V 132V C Auto 120V 144V D Auto 120V 100V D Auto (reverse input &
- 31. BUCK BOOST “AUTO” DIAGRAMS
- 32. QUESTIONS?
Editor's Notes
- Title Slide for ACME Brand. Photo/image area is defined by the photo box. The photo box can be substituted with imagery relevant to your subject.
- DISCUSS NAMEPLATE SPECIFICATIONS EMPHASIZING PRIMARY AND SECONDARY VOLTAGE DIFFERENCES. WHEN FIELD CONNECTED AS “AUTO” TRANSFORMERS THE SECONDARY VOLTAGE “ADDS TO” OR “ SUBTRACTS FROM” THE SUPPLY VOLTAGE. REVIEW “ISOLATION” VS “AUTO” CONNECTIONS FROM BASIC THEORY SEMINAR IF NECESSARY.
- AN ISOLATION TRANSFORMER IS ONE IN WHICH THE SECONDARY WINDING IS ISOLATED OR “INSULATED” FROM THE PRIMARY WINDING. IT MAY OR MAY NOT CONTAIN AN ELECTROSTATIC SHIELD BETWEEN THE WINDINGS. AN “AUTO” TRANSFORMER IS ONE IN WHICH THE SECONDARY AND PRIMARY WINDINGS ARE ELECTRICALLY CONNECTED TO EACH OTHER. BUCK - BOOST TRANSFORMERS COME OUT OF THE BOX AS ISOLATION TRANSFORMERS BUT GET FIELD CONNECTED AS “AUTO’S”. MAJOR ADVANTAGES OF “AUTO’S” ARE THAT THEY ARE SMALLER IN SIZE, LIGHTER, AND LESS EXPENSIVE THAN COMPARABLE ISOLATION UNITS.
- THIS PRINCIPLE IS THE BASIS FOR UNDERSTANDING THE OPERATION OF BUCK-BOOST TRANSFORMERS. WHEN CURRENT FLOWING IN A SINGLE CONDUCTOR REACHES A POINT WHERE IT CAN DIVIDE AND NOW FLOW IN TWO SEPARATE CONDUCTORS, HOW WILL IT DIVIDE? IT WILL DIVIDE BASED ON THE RATIO OF THE RESISTANCES OF THE TWO WIRES. IF THE CONDUCTORS ARE THE SAME RESISTANCE (SIZE), THEN THE CURRENT WILL DIVIDE 50% AND 50%. IF ONE CONDUCTOR IS TWICE AS LARGE AS THE OTHER THEN THE CURRENT WILL DIVIDE 66.6% AND 33.3%. IF ONE IS THREE TIMES AS LARGE AS THE OTHER THEN THE CURRENT WILL DIVIDE 75% AND 25% AND SO FORTH. THIS CONDITION IS WHAT WE HAVE WHEN WE “AUTO” CONNECT THE BUCK-BOOST TRANSFORMER BY CONNECTING A SMALLER PRIMARY WIRE TO A LARGER SECONDARY WIRE. THE LARGER WIRE WILL CARRY THE MOST CURRENT.
- A TRANSFORMER RATED 1 KVA ON THE NAMEPLATE MEANS THAT THE PRIMARY AND SECONDARY WINDINGS ARE EACH RATED AT 1 KVA. 1 KVA = 1000 VA 1000 VA DIVIDED BY 100 V = 10 AMPS 1000 VA DIVIDED BY 10 V = 100 AMPS NOTE: IN ANY CIRCUIT THE INPUT KVA WILL BE EQUAL TO THE OUTPUT KVA.
- IN A BOOSTING CONFIGURATION, THE WINDINGS ARE SERIES CONNECTED SO THAT THE PRIMARY AND SECONDARY VOLTAGES WILL BE ADDED. WHEN AUTO CONNECTED THE 100V PRIMARY AND 10V SECONDARY ADD TO DELIVER 110V OUT.
- IN THIS CONFIGURATION THE 1 KVA RATING IS INCREASED TO 11 KVA AS A RESULT OF THE AUTO CONNECTION. NEW KVA = OUTPUT VOLTS X RATED SECONDARY WINDING AMPS DIVIDED BY 1000. = 110 X 100 / 1000 = 11 KVA SINCE INPUT AND OUTPUT KVA ARE THE SAME, THE INPUT AMPS WOULD BE: 11,000 VA / 100 V = 110 AMPS HOW CAN THIS TRANSFORMER WITH A PRIMARY ONLY RATED FOR 10 AMPS HANDLE THIS 110 AMPS OF CURRENT? IT DOESN’T, BECAUSE WHERE WE JOINED THE PRIMARY AND SECONDARY WINDINGS THE 110 AMPS DIVIDES INTO 100 AMPS IN THE SECONDARY AND ONLY 10 AMPS IN THE PRIMARY.
- REVIEW INFORMATION IN CATALOG ABOUT SELECTING THE PROPER BUCK-BOOST TRANSFORMER REVIEW SELECTION CHARTS IDENTIFYING DIFFERENCES BETWEEN VOLTAGES AND ALSO BETWEEN SINGLE AND THREE PHASE. DISCUSS NOTE ABOUT REVERSE CONNECTING AT BOTTOM OF PAGE. IF LOAD IS GIVEN IN HORSEPOWER, YOU MUST FIRST USE TABLES 2 OR 4 FROM SECTION 1, OR USE YOUR KVA CARD TO DETERMINE KVA. FOR BEST RESULTS, THE LINE VOLTAGE SHOULD BE THE ACTUAL MEASURED VOLTAGE NOT THE NOMINAL CIRCUIT RATING!
- TURN TO 1-PHASE SELECTION TABLES AND FIND LINE AND LOAD VOLTAGES ACROSS TOP OF CHART. HINT: WHETHER TO USE WHICH VOLTAGE GROUP CAN BE DETERMINED BY FINDING THE DIFFERENCE BETWEEN LINE AND LOAD VOLTS. (IN THIS CASE 208 - 189 = 19 VOLTS) AND COMPARE WITH SECONDARY VOLTAGE OF EACH GROUP FOR NEAREST EQUAL TO OR GREATER THAN VALUE.
- SELECT THE DESIRED LINE AND LOAD VOLTAGE COMBINATION ACROSS THE TOP OF CHART. SINCE THE LOAD WAS STATED IN KVA, READ DOWN THE COLUMN TO THE DESIRED KVA RATING. IF THE EXACT VALUE IS NOT FOUND, GO TO THE NEXT HIGHER VALUE. READ TO THE FAR LEFT TO GET CORRECT CATALOG #. IN THIS CASE IT WOULD BE T181051. GO BACK TO THE DESIRED VOLTAGE COLUMN AND READ DOWN TO THE BOTTOM TO FIND THE CORRECT WIRING DIAGRAM. IN THIS CASE IT IS FIG. H. WIRING DIAGRAMS ARE ON LAST PAGE OF SECTION 8.
- EXPLAIN THAT INPUT IS APPLIED TO PRIMARY WINDING ONLY AND THAT OUTPUT IS ACROSS BOTH PRIMARY AND SECONDARY. AS STATED PREVIOUSLY “OUTPUT MINUS INPUT” = VOLTAGE OF SECONDARY WINDING. IN THIS EXAMPLE WE ARE APPLYING 189 V TO A 240 V WINDING 0R 78.7% OF RATED VOLTAGE. SINCE TRANSFORMERS ARE JUST RATIO DEVICES, WE WILL GET 78.7% OF THE SECONDARY RATED VOLTAGE. IN THIS CASE 78.7% OF 24 V = 18.9 V. BOOSTING OUTPUT WILL = INPUT (189 V) + SECONDARY VOLTS (18.9) FOR A TOTAL OF 208 V. REVIEW: ASK WHAT HAPPENS TO INPUT CURRENT WHEN IT REACHES THE CONNECTION AT H1-X4. (HOW WILL IT DIVIDE?) IT WILL DIVIDE BASED ON THE RESISTANCES OF THE TWO WIRES!
- FIND LINE AND LOAD VOLTAGE COMBINATION IN SELECTION CHARTS. HINT: 240 V - 208 V = 32 V. SEE NEXT SLIDE.
- FIND DESIRED VOLTAGE COMBINATION ACROSS TOP OF CHART. READ DOWN THE COLUMN UNTIL YOU FIND A VALUE OF 60 AMPS OR GREATER. YOU WILL FIND 62.5 AMPS. NOW READ TO THE FAR LEFT TO FIND CATALOG # T113075. READ DOWN TO BOTTOM OF VOLTAGE COLUMN TO FIND WIRING DIAGRAM FIG. H. WIRING DIAGRAMS ARE ON LAST PAGE OF SECTION 8. NOTICE THAT KVA OF THIS UNIT CONNECTED PER FIG. H FROM THE CHART IS NOW 15 KVA, WHILE THE UNIT NAMEPLATE SAYS IT IS ONLY RATED 2 KVA. THIS IS A 7.5 TIMES INCREASE AS A RESULT OF THE “AUTO” CONNECTION.
- IN THIS EXAMPLE WE ARE APPLYING 208V TO A 240V WINDING OR 86.6% OF RATED VOLTAGE. SINCE THE SECONDARY OF THIS UNIT IS RATED AT 32V WE WILL ONLY GET 86.6% OF 32V OR APPROX. 28 VOLTS. OUTPUT USING FIG. H WILL BE 208V + 28V = 236V. THIS WAS ROUNDED UP TO 240V IN THE SELECTION CHART.
- NOTE THAT THIS IS A BUCKING APPLICATION. AS IN PREVIOUS EXAMPLE 240V MINUS 208V = 32V. SEE CHART ON NEXT SLIDE.
- FIND DESIRED VOLTAGE COMBINATION ACROSS TOP OF CHART IN THE BUCKING SECTION. READ DOWN THIS COLUMN UNTIL YOU FIND A KVA VALUE OF 14 KVA OR GREATER. READ TO THE FAR LEFT TO FIND CATALOG # T113075. THIS IS SAME UNIT CHOSEN FOR EXAMPLE # 2. LOOK AT BOTTOM OF VOLTAGE COLUMN TO FIND WIRING DIAGRAM FIG. I. DIAGRAMS ARE ON LAST PAGE OF SECTION 8.
- SHOW THAT FIG. I IS REALLY NOTHING OTHER THAN A REVERSE CONNECTION OF FIG. H. THIS COMPLETE APPLICATION IS ONLY A REVERSE CONNECTION OF EXAMPLE # 2. SEE NOTE AT BOTTOM OF CATALOG PAGE , ABOUT REVERSING INPUTS AND OUTPUTS.
- NOTE THAT THIS IS A 3-PHASE APPLICATION. AS NOTED EARLIER 230V MINUS 208V = 22V SEE NEXT SLIDE.
- FIND DESIRED VOLTAGE COMBINATION ACROSS TOP OF CHART. READ DOWN CHART UNTIL YOU FIND A KVA VALUE OF 80 KVA OR GREATER. IN THIS CASE YOU FIND 82.99 KVA. READ TO THE FAR LEFT OF CHART TO FIND CATALOG # T111687. LOOK AT BOTTOM OF VOLTAGE COLUMN TO FIND QUANTITY REQUIRED AND WIRING DIAGRAM TO USE. IN THIS CASE YOU NEED 2 PIECES AND THE WIRING DIAGRAM IS FIG. B-B. YOU WILL SEE THAT THE T111687 IS ONLY RATED AT 5 KVA ON ITS NAMEPLATE AND YET 2 OF THEM CONNECTED PER FIG. B-B WILL YIELD 82.99 KVA. IF THIS APPLICATION WERE DONE USING AN “ISOLATION” TRANSFORMER OF STANDARD KVA RATING IT WOULD REQUIRE A RATING OF 112.5 KVA. (POINT OUT APPROXIMATE COST DIFFERENCE BETWEEN 2 PCS OF 5 KVA AND A 112.5 KVA).
- NOTICE THAT FIG. B-B USES TWO SINGLE PHASE UNITS TO PERFORM THREE PHASE WORK. THIS TYPE OF CONNECTION IS KNOWN AS AN “OPEN DELTA”. A CLOSE LOOK AT EACH TRANSFORMER IN FIG. B-B WILL SHOW THAT EACH ONE IS WIRED PER FIG. H FROM THE SINGLE PHASE DIAGRAMS. THEY ARE THEN JOINED AT THE “H4” TERMINALS.
- IN ANY OF THESE APPLICATIONS AS WELL AS MANY OTHERS, A LOW VOLTAGE CONDITION CAN CAUSE SEVERE PROCESS AND EQUIPMENT PROBLEMS TO OCCUR. BUCK-BOOST TRANSFORMERS OFFER AN ECONOMICAL SOLUTION TO MANY LOW VOLTAGE PROBLEMS.
- TYPICAL ISOLATION VOLTAGES - 240 TO 120, 480 TO 240, 480 TO 120, 600 TO 240, 600 TO 12O, ETC. TYPICAL BUCK-BOOST VOLTAGES - 100 TO 120, 200 TO 220, 208 TO 230, 208 TO 240, 230 TO 277, 460 TO 480, ETC.
- AS YOU SEE FROM THIS CHART, UNDERVOLTAGE AFFECTS MOTOR OPERATION IN TWO WAYS: 1. 15% LOW VOLTAGE RESULTS IN 17% INCREASE IN CURRENT FLOW. 2. 15% LOW VOLTAGE RESULTS IN 38% INCREASE IN MOTOR TEMPERATURE. A 15% LOW VOLTAGE IS APPROXIMATELY THE SAME AS RUNNING A 240 VOLT MOTOR AT 208 VOLTS.
- INCREASED CURRENT FLOW CAN CAUSE EXTRA HEATING IN CONNECTING WIRES AND JOINTS, AND ALSO CAUSE FUSES TO BLOW OR CIRCUIT BREAKERS TO TRIP. HEAT IS A BY-PRODUCT OF WATTAGE, WHICH IMPLIES THAT THE INCREASED TEMPERATURES ARE A RESULT OF CONSUMING MORE ENERGY. AFTER ALL, YOU ARE PAYING THE UTILITY FOR KILOWATT HOURS OF ELECTRICITY. EFFECTS ON TORQUE ARE SHOWN ON NEXT SLIDE.
- THIS CHART SHOWS THAT TORQUE DECREASES EXPONENTIALLY IN RELATION TO A DECREASE IN VOLTAGE. TORQUE AT 90% = (.9) SQUARED = .81 OR 81% TORQUE AT 80% = (.8) SQUARED = .64 OR 64% A RELATIVELY SMALL DROP IN VOLTAGE CAN REDUCE TORQUE TO THE POINT WHERE THE MOTOR IS NOT ABLE TO START UNDER LOAD.
- THESE ARE SOME OF THE MORE COMMON CAUSES OF VOLTAGE MISMATCH. WE HAVE SEEN ELECTRICAL SYSTEM UPGRADES WHERE A 208Y/120 SYSTEM HAS BEEN USED TO REPLACE A 240 DELTA! THIS RESULTS IN THE THREE PHASE VOLTAGE BEING 13% LOW. VOLTAGE DROPS ARE COMMON WHERE CABLES ARE RUN OVER LONG DISTANCES. EQUIPMENT OFTEN ARRIVES WITH 230 OR 240 V MOTORS WHEN THE SUPPLY VOLTAGE IS ONLY 208. UTILITIES WILL SOMETIMES CUT BACK ON VOLTAGE FOR LONG PERIODS OF TIME TO HANDLE DEMAND REQUIREMENTS.
- WE HAVE ALREADY SEEN HOW A BUCK-BOOST TRANSFORMER WITH A NAMEPLATE RATING OF 1 KVA COULD BE AUTO CONNECTED TO DEVELOP 11 KVA OF CAPACITY. THIS SLIDE ILLUSTRATES THE TYPICAL SIZE DIFFERENCE BETWEEN AN ISOLATION AND AN “AUTO” TRANSFORMER FOR THE SAME APPLICATION. THE BUCK-BOOST TRANSFORMER WILL ALSO HAVE CONSIDERABLY LOWER LOSSES THAN THE ISOLATION UNIT, RESULTING IN MORE EFFICIENT OPERATION AND LOWER OPERATING COST. (NAMEPLATE RATING OF BUCK-BOOST UNIT IS ONLY A FRACTION OF THE APPLIED LOAD RATING) IT ALSO HAS A MUCH LOWER PURCHASE PRICE!
- ALL ACME BUCK-BOOST TRANSFORMERS HAVE UL 3R OUTDOOR ENCLOSURES WHEN MOUNTED VERTICALLY. THEY ARE ALLOWABLE UNDER THE NEC. SEE QUESTIONS AND ANSWERS IN SECTION 8. THE SELECTION TABLES IN THE CATALOG OFFER ONLY THE MORE COMMON VOLTAGE COMBINATIONS. PLEASE CONTACT THE FACTORY AT (800) 334-5214 FOR OTHER VOLTAGE REQUIREMENTS.
- Closing Slide.