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Industrial transformers
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Buck boost transformers and Industrial transformers Inputs and outputs are AC |
| Section I. Buck Boost Transformers |
 Buck boost transformers have 2
functions depending how they are wiredA) wired as isolation transformer or B) wired as autotransformer Buck-boost transformers are dry-type transformers with 4 coils of wire that are located inside a steel Nema 3R weather-resistant enclosure. You can use one transformer for single-phase applications, or use three of the same transformers for 3-phase. Connecting the 4 coils of wire together are key. There are 4 coils or windings of wire inside the transformer. Each coil has two ends of wire, with 8 total ends that are labeled, H1 H2, H3 H4, X1 X2, X3 X4. The 8 coils can be connected to make either A) isolation transformer or B) autotransformer. |
Buck Boost A) When wired as an ISOLATION transformer, all four of the H coils are connected to the input voltage, or primary side, and all four of the X coils are connected to output voltage, or secondary. This wiring creates 2 isolated, or separated coils, The H coil and the X coil, and neither coil shares a wire in common with the other coil. This wiring would be a step-down transformer.  In this configuration, the Buck-boost transformer is used to convert 480-240-120 input voltage on the primary side into 12, 16, 24, 32 or 48 volt AC output voltage on the secondary side. Typical application, the outputs 'are used to power low voltage circuits including control, lighting circuits, or applications that require 12, 16, 24, 32 or 48 volts." For example, a commercial building might have 480 volt lights, but the switching is 24 volt. For this application, the correct model buck boost transformer is chosen to convert 480 volt input into 24 volt output for the switches. Choosing the correct model transformer is done using a wiring chart provided by manufacturer, and the correct model depends on the input voltage (120-240-480 volt) and output voltage (12 to 48 volt). Resource: Wiring chart Household usage Typical household use for a Buck Boost would be to step 120 or 240 volt down to 12 to 24 volt AC |
Buck Boost B) When wired as an AUTOTRANSFORMER, all four of the H coils and all 4 of the X coils are wired together to make one single coil, with inputs and outputs connected at different points along the single coil. When the Buck Boost is wired onsite as an autotransformer, it will step up (increase) or buck down (decrease) voltage by 5-20%.  This would be the correct use of a Buck Boost if voltages are lower or higher than needed. For example if a motor is rated for 240 volt, but actual voltage at the location is 206 volt, then the undervoltage will damage the motor. To solve problem, a Buck Boost would be selected based on the voltage needed, then wired as autotransformer so the 4 coils will boost 206 nearer to 240 volt. Another use would be to step up 240 volts to 277 volts etc. For example the commercial building has 240 volt service, but wants to use 277 volt lighting. Selecting the right buck boost transformer is done using charts that show a range of input and output voltages ... for example input of 240 volt and output of 277 volt ... the electrician would use the charts to select the nearest voltage ... then use a second set of charts to determine correct wiring. Resource: Wiring charts for buck boost transformers start pg 6 Household usage Household use would be to boost a voltage drop (frequently caused by long run of wire) up to standard voltage |
 Buck-boost/
More detail isolation transformerFig B4 shows 2 of 4 possible buck boost isolation transformer wiring diagrams for converting 120-240-480 volt input into low voltage output. All transformers must be grounded. How isolation transformers work. Inside each transformer are the primary and secondary coils (windings). The 480-240-120 input voltage connects to the primary side, and the transformer converts high voltage into low voltage: 12, 16, 24, 32 or 48 volt AC output on the secondary side. Each coil is wrapped around an iron core (represented by double line). The iron core is shared by both primary and secondary sides. When power is applied to the primary coil, it magnetizes the shared iron core, which induces power on the secondary coil even though the primary and secondary share no wire in common. This is called magnetic induction. If the number of turns of wire on the primary side are exactly twice as many as on the secondary side, then the voltage is lowered by 1/2. Varying the turns ratio lets transformers deliver a variety of voltages. The isolation transformer coils (or windings) are electrically separated (or isolated) from each nother because they share no wire in common. Note: when wired as insulating or isolation transformer, a transformer can deliver only the rated kVA and shouldn't be overclocked without risk of overheating and damage to transformer. Resources: kVA is Kilo watts: 1 kilo watt is 1000 watts, so .5 kVA is 500 watts Va = volts x amps = watts Siemens transformers/ pdf Read about household single-phase electricity Difference single-phase and 3-phase What is 3-phase How to wire 3-phase timers |
 Buck-boost/
More detail autotransformerFig B5 shows 3 of 8 possible autotransformer wiring diagrams for single-phase to achieve different voltages. When buck boost is wired as autotransformer, it can solve commercial electric problems. 1) Problem with Non-standard voltages. Voltages are generally stable, but they vary, and can be different at each location, especially with longer distance from service box. Low voltage and high voltage affect operation and efficiency of electrical equipment. The buck boost can bring voltages into standard. 2) When higher or lower standard voltage is needed. Commercial electric services offer a variety of standard voltages, including 120, 208, 240, 277, 480 etc. If the service is 120-240-208 high leg delta, but 277 volt is needed for the lighting, then a buck boost transformer can solve the problem. 3) Need more kVA than the rating plate. Autotransformers can deliver up to 10 times more kVA than the transformer rating plate, and run quieter, and cooler with less heat loss and with higher efficiency. Note if voltages vary, then the transformer does not stabilize voltages ... nor protect from surge events, or correct uneven voltage across each leg etc Note: Buck boost cannot create a Neutral, like industrial transformers shown lower on page. A 4-coil buck boost transformer can be wired as an autotransformer to buck up (raise) or buck down (lower) single phase or 3-phase voltages by 5-20%. This is accomplished by connecting all 4 coils together to form a single coil, and then pulling a wire off center connection point as illustrated in Fig B-2. Autotransformers are sometimes prohibited by local electric codes because voltages are not electrically separated or insulated from each other like you have with insulating transformers ... except buck boost transformers only change the voltage by a small percent, which means only a small risk. Contrast buck boost with industrial transformer that is designed to step 480 volt down to 240 volt. If the industrial transformer is wired as autotransformer, and transformer suffers an internal failure, then the 240 volt wires could be unexpectedly energized with highly dangerous 480 volt. The buck boost transformer does not pose same level of danger when wired as autotransformer. Compare buck boost transformers wired as insulating transformers, vs being rewired as autotransformer where the primary and secondary windings are not insulated from each other, and an insulation failure can result in primary voltage energizing the secondaries.. "Why can a buck-boost transformer operate a kVA load many times larger than the kVA rating on its nameplate" when wired as autotransformer? Buy: 150 watt Square D 120-240 volt to 24-12 volt Square D buck boost Buck boost transformer Siemens transformer at Amazon 240-120 buck boost transformer Note: If 12-24 volt DC current is needed instead of AC, then an LED driver is used. Buy: LED driver |
| Section II. Encapsulated Transformers | |
 Larger imageEncapsulated Industrial transformers/ Typical household use would be to step 240 volt down to 120 volt. Also called dry type distribution transformer. These 4-coil insulation transformers are for single phase or 3-phase applications where input can be 240 or 480 volt, with output of 240 volt or 120 volt. Inputs and outputs are AC and not DC. Buy: 500 watt 240-120 volt step down 1000 watt 240-120 volt step down 1000 watt step down 2000 watt 240 volt to 120 volt step down Encapsulated transformers Select right wattage kVA is kilo volt amps ... since volts x amps = watts (power), then kVA = 1000 watts. Make sure that selected transformer is rated for more kVA than your load (motor, lights, etc). Look at volt and watt rating of load and this will indicate which transformer is correct. So if load is rated 1200 watts, then that means 1.2 kVA, and so 2000 watt or 2 kVA transformer is correct choice. Transformers get hot when in use. If a transformer is rated lower wattage than your load, the transformer will overheat and eventually stop functioning. Note the steel enclosure does not get hot but can get warm. According to
electric code the "frequency and duration of loading cycles determine a
transformer's life." A transformer can 'deliver short term overloads
without being damaged if the overload is preceded and followed by
reduced loads.' This means you can run 1200 watts load off a 1000 watt
(1 kVA) transformer for short durations, but not recommended unless
transformer is used sparingly remainder of time. Recommended best to
buy a transformer that is rated higher kVA than needed, giving excess
capacity for expansion.
Maximum 'ambient air temperature 86-104°F ... altitude 3300 feet for normal operation." Resource: Siemens transformers pg 4  InstallationAccess internal wiring by removing cover. Open 1 or 2 knockouts located on side of transformer. Insert a conduit or wire clamp in the knockout hole. Attach transformer to structure. Turn power OFF. Run wires into transformer through the knockout. Make wiring connections inside the transformer using ordinary twist on wire connectors same as any electrical connection. Reattach front cover. Turn power ON. Buy: Power whip Resources: Acme transformer wiring Dry transformer installation Wiring diagrams for step down 240V to 120V   When ordering a 240-to-120 step down transformer: "If the dual voltage is separated by an “X” (120 x 240), the transformer can be connected only for 240-to-120 volts, and the wring diagram shows in Fig 55 ... and shown in Acme-1 wiring diagram at the green arrow. 240 volt primary wiring shows at red arrow.  "If the dual voltage it is separated by a “slash” (120/240), an additional connection is possible on secondary side since the mid-point becomes available for 240/120 3-wire operation" as illustrated in Fig 66 ... and shown in Acme-1 wiring diagram at the blue arrow. 240 volt primary wiring shows at red arrow. Resource pdf pg 4 Reverse wiring/ For residential purpose, this means a person can reverse-wire a 1000 watt (1kVA) Acme transformer and convert 120 volt input to 240 volt. -Any industrial transformer can be wired in reverse to step up voltages (from 120 volt to 240 volt, or 240 volt to 480 volt). Acme manual says: "Transformers rated 1 kVA and larger single phase, 3 kVA and larger three phase can be reverse connected without any adverse effects or loss in kVA capacity." This means if you have a 1000 watt or larger industrial transformer, you can wire in reverse and convert 120 volt into 240 volt where the X connections become the primaries (input voltage), and H connections are the secondary (output voltage), but you must pay attention to amp rating of load plus wire and breaker size on the incoming 120 volt line.  480 volt
is a commercial voltage and never used inside a
residential home for any purpose.Do not buy 240-480 volt transformer for use at residence. If you have a 240-480 transformer or have an unmarked transformer, be extra careful ... unless you are qualified electrician, never connect one of these transformers in reverse where 240 is converted into 480 volt output ... 480 volts is extremely dangerous and will kill instantly just by touching live power, even if you are not grounded. More detail  Autotransformer-Note 4-coil (4 winding) encapsulated transformers can be wired as autotransformer. Illustration shows 480 volt commercial power with step down to 240 volt. -For residential applications, the insulation transformer wiring shown above is correct because insulation transformer insures the low voltage wires can never be energized by high voltage. However, the kVA rating (kilowatt) goes up when a transformer is wired as an autotransformer. This means that an industrial transformer can be wired as autotransformer and deliver considerably more kVA than the nameplate. Autotransformers are prohibited by many local codes because the primary and secondary voltages share a common wire, and there is a risk of lower voltage lines becoming dangerously energized by the higher voltage. |
| Section III. Industrial Control Transformers | |
 Size varies by kVA output: 5.1 x 5.6 x 3.6 inches ; 3 pounds   |
Siemens
industrial transformers Typical household use would be converting 240 volt to 120 volt. Another use would be to convert 240 volt into 24 volt AC. The 4-coil transformers shown above on this webpage come with a Nema 3R steel enclosure made for indoor-outdoor installation, and the wiring is completed inside the enclosure using twist on wire connectors. The 4-coil epoxy-encapsulated 50-60 Hz industrial transformer or power transformer or control circuit transformer shown on left has simple wiring with 10-32 screw terminals but requires an enclosure -or- it can be installed inside existing enclosure. Siemens power transformers are inexpensive and reliable with 120 to 600 volt inputs and 24V, 120V, 240V AC outputs ranging from .05Kv (50 watt) to 5Kv (5000 watt) etc. Fuse block can be added to top of transformer, and would protect transformer from overvoltages. A fuse clip is standard on most models for the output voltages ... and would protect entire length of circuit on secondary side. Buy: Siemens industrial transformers Choose enclosure that is large enough Bud industries hinged box 6x8x4 Metal outdoor Enclosure/ with 1/2-3/4" knockouts Polycarbonate enclosures drill for knockouts Thomas and Betts 6x6x4 plastic with cover at Amazon Bud industries 11x7x5 box no knockouts Tapered drill bit 1/4"-1-3/8 holes  Example Nema 3R indoor outdoor enclosures   Resources: Siemens control transformers Siemens transformers |
  Example
wiring diagram for transformerIf the input voltage is 220-230-240 volt, then connect one wire to terminals H1 and H3, connect other wire to H2 and H4. Output on X1 X2. Optional fuse clip. If input voltage is commercial 440-460-480 volt (480 for Americas), then connect one wire to H1 and other wire to H4, then jumper a wire between H2 and H3. Larger image of transformer Buy: Siemens MT0050 industrial transformer Note: 60 Hz Hot to Hot 240 volt is for power grid in Americas, 50 Hz Hot to Neutral 230 for Europe, and 50 Hz Hot to Neutral 220 for Australia etc. |
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| Section IV: Low Voltage Transformers | |
 Intermatic PX series 120 volt AC transformers with Nema 4X enclosure are rated for harsh conditions, exposure to water and humidity and chemicals, and used for interior or exterior installation. Typical household use for 300-600 watt PX series transformer would be to step 120 down to 12, 13, 14 volt AC for pool lights, interior low voltage light, low voltage pathway lights etc.  Buy:PX100 100 watt multitap with choice of 12-13 volt PX300 300 watt multitap with choice of 12-13-14 volt PX600 two 300 watt transformers in one 12-13-14 volt AC 12 volt swimming pool light Pool cleaning equipment Buy Low voltage cable Note: If 12-24 volt DC current is needed instead of AC, then an LED driver is used. Buy: LED driver These 300-600 watt transformers are designed for 120 volt input only, and have 'multi-tap' 12-13-14 volt AC output for pool equipment and other low voltage applications such as pathway lights etc. Multi-tap means there is a choice of three output wires, each gives slightly different voltage. Use higher voltage if distance is farther or there are more lights, use lower voltage for fewer lights or less brightness. Resources: Distance chart PX300 manual Intermatic sells parts for their transformers: Resources: Parts sheet1 Parts sheet -Best if transformer is located out of direct sun where heat can shorten life of any electrical installation. The Intermatic series has thermal fuse that trips to prevent transformer from overheating. The fuse automatically resets when temperature of transformer cools. -PX series transformers are manufactured specifically for electrical safety. The Intermatic series has a a safety shield between the primary and secondary side that is designed to electrically separate or insulate the incoming 120 volt power from low voltage wires that go to pool. This ensures that low voltage wires going to the pool or to lights cannot be energized with high voltage. Resource: Spec sheet Safety-Never use 120 volt lights under water, or where wires or connections might come into contact with the pool or any pool liner ... even if wires are properly insulated. Why? Because insulation failure of coatings surrounding a wire are not uncommon with nearby lightning strike or short circuit. The result will put high voltage into the water that will cause electrocution if a person comes in contact. -Never depend on GFCI for 100% protection. GFCI must be properly grounded, and must be tested before each use by pushing test and then reset buttons. Ungrounded GFCI will not trip immediately, and while an ungrounded GFCI will usually protect person, there is no guarantee. Two prong extension cords, and double insulated tools do not give complete protection even if plugged into GFCI. Always use 3-prong extensions cords and grounded power tools when working outdoors. -Always use conduit for outdoor 120-240 volt wiring. Use approved 600 volt cables and wires for 120-240 volt household wiring. It is against code to use extension cord for permanent wiring. Resource: Color code for residential wiring PX series transformer output gives choice of 12-13-14 volt AC .... use higher voltage for longer lengths of wire or brighter lights or when more lights are used. Use larger wire for best result ... choose 12 gauge instead of smaller gauge 14. Resources: Low voltage transformers swimming pool lights / wiring |
| Primary-secondary Industrial transformers and Buck-Boost Transformers are rated for heavy-duty commercial use ... but can be used for residential applications without problem as long as transformer is rated for 60 Hz in US, and input voltages are 120-240V and output 24-120-240V consistent with residential AC power. All transformers have primary and secondary windings (coils) ... with the primary side for incoming voltage ...and secondary side for output voltage. By definition, the primary coil is whichever is used to connect incoming power. For example a residential transformer on the grid receives 7200 volt on the primary side, and delivers 120-240 to the residence from the secondary side of transformer. However, if home has solar panels, and the panels are producing more power than used by residence, the solar-produced electricity sends 120-240 to the power company transformer. The transformer uses the 120-240 to produce 7200 volt ... and when this happens, the primary side is on the residential side of transformer and the secondary is on the power company side. Efficiency Transformer loss can range from .5 to 8%, meaning 92-98% efficiency. Efficiency losses come from "eddy currents that are magnetically induced on the iron core and hysteresis loss, or heat loss, from iron atoms in the core resisting polarity change when the atoms realign with changing polarity caused by oscillating current, plus loss from resistance of the winding (wire) itself." Higher amp draws and high heat locations cause lower efficiency and shorten life of any electrical installation. Noise level Transformers have humming sound ranging from 40-66 dB / while 70 dB is annoying and 100 dB is very loud. The higher the kVA rating of transformer, the louder the sound. Note that sound can be magnified if transformer is installed against wood etc. Transformers as a general rule, have long life expectancy if kept within the kVA capacity and not overclocked excessively. They are reliable, have no moving parts, and no repairs are needed or possible. Hertz or cycles The number of rotations per second of the power plant generator is called Hz (hertz) or cycles or frequency, and appears on label of each electrical transformer, timer, appliance, motor etc. The US and American use 60 Hz, while rest of world has 50 Hz. Transformers that are rated 50-60 Hz can be used worldwide, but a transformer rated 50 HZ will not work for 60 Hz power in the US., or vice versa. Voltage also vary by country. While 60 Hz hot-to-hot 240 volt are standard in the US, other countries like Britain can have 50 Hz hot-to-neutral 230 volt etc.  Multi-tap transformersFig M-1 shows example of multitap transformer that lets electrician choose best match for primary and secondary voltages. Fig M-1 illustrates an insulation transformer. Incoming voltage on primary side connects to H4 and to one of the other taps. This means only two wires are connected to primary side. Likewise on secondary side, only two wires are used, one connected at X3 and the other at the selected voltage.  Fig M-1 shows H1 tap at 600 V. Note: 600 volt is the highest possible electric service that is available for commercial applications, and by code 600 volt is the standard rating required for electrical devices and electric cable. Fig M-2 illustrates a multitap autotransformer. Same as insulation transformers, only two wires connect to input side, and two wires on output side.Unused wires are capped off. |
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