Transformer insulation is generally rated for 220°C but may be lower for some designs including control or encapsulated. Standards permit the temperature of the transformer enclosure cover to be 65°C over ambient. When temperatures exceed the rating for the insulation system or enclosure, overheating occurs. Burned, darkened or damaged insulation may be apparent along with a burnt smell. The hottest part of a transformer is the coil near the top of the core. Energized transformers should not be touched. If the insulation is damaged or smoke is visible, the unit may need to be returned for testing and replaced or repaired. Verify total load doesn’t exceed transformer kVA rating. Reduce size or load or replace with larger transformer. In some cases fans can be added to increase cooling and Verify ambient temperature does not exceed transformer ratings. Relocate to area with lower ambient temperature, reduce load, reduce ambient temperature at primary location or

replace with a low temperature rise transformer. Transformers installed in small rooms will need proper room Verify tap connections are set up identically on all coils. Verify transformer is correctly rated for harmonic load, check for high neutral currents. Reduce or remove harmonic loads or replace transformer with a larger unit or unit with the proper k-rating. Verify that the transformer’s ventilation openings are not blocked. Transformers purchased as core and coil units and placed in enclosures not supplied by HPS require that the integrator properly size the enclosure and cooling Relocate the transformer to an area of better ventilation. Move the transformer away from walls, equipment or overhead projections that may impede airflow. Do not install fans to cool a transformer. Improperly installed fans may actually impede airflow and could result in transformer damage. Verify taps are correctly set for the input voltage. Depending on the load and transformer type, continuous

overvoltages or undervoltages as low as 5-10% may cause overheating. Check no load current. If no load current is high (varies with transformer efficiency but no load current is typically less than 2-3% of total kVA), inspect the core and coils for damage. In most cases you will not be able to inspect the insulation between the core and coil without returning to the factory for testing and disassembly. Cork Under Hardwood FlooringIf there is a short between the coreHow To Hang Heavy Mirror No Studs and coil, the unit will have to be replaced or repaired.T Shirts With Tapered Sleeves Excessive and sustained airflow caused by exterior winds or fans generally moving horizontally to the ground can disrupt convection cooling and cause overheating at high loads.

Relocate the transformer to an area with less wind or block the wind. Fan cooled transformers have broken or misaligned fans. Fans need to be replaced or realigned. Low power factor can cause excessive current and higher overall loads. Current meters need to be able to registerSome digital meters may not be accurate. Unbalanced loads may cause excessive heating. Loads should be balanced to within 20 % of maximum kVA. No individual load should exceed the load specific load for each phase (1/3 of total kVA for three phase units). Transformer is installed above a heat source such as another transformer. Move either the transformer or the heat source. Redirect the hot airflow from the lower object away from the cooling entrances and surfaces of the higher object. Replace the top unit with a low temperature rise transformer. Check if output voltage is distorted. A highly distorted output voltage may be a sign that there is a turns to turns fault and the transformer is in

danged of immediate failure. The transformer needs to be denergized and meggered. The damaged coil may need to be replaced or the transformer scrapped. Check the output circuits to make sure each leg of the transformer is functioning and overcurrent protection is If a fuse on one or more of the legs has opened, determine and clear the fault and replace the fuse. commong on delta transformer outputs, especially if three single phase units are used in a Delta bank. If a Drive Isolation Tranformer (DIT) is being used, verify the DIT kVA has been derated per the HP sizing charts in the catalog. If motor HP is unknown, use .746 kW/HP to determine the equivalent HP of the load. DIT’s are not current rated devices, the HP selection charts must be used to properly size a DIT. Extrusion applications tend to be the worst. Check if two or more transformers are operating in parallel to power one load. Transformers operating in parallel are rare. Large circulating currents and uneven load can result from

transformers wired in parallel. The transformer s may have to replaced with one unit capable of power the entire Cable connections are discolored by heating. Cables should be periodically tightened. The surface should be cleaned of any insulation applied during the vacuumRough edges must be smoothed. Sparks or smoke is visible from the base of the transformer but the transformer has not failed and there isn’t any sound of arcing. During the VPI process, icicles of insulation can form under the tarnsformer and occassionally act as a ground. discovered early enough the icicle can be removed and the transformer will not be damaged. Excessive dust could block air vents Dust needs to be blown out while transformer is denergized. The transformer’s insulation may have been damaged and may need to be repaired or replaced. Visible Flames or SmokeLow-Voltage Lighting Systems Operating at 30 Volts or LessLow Voltage General Purpose Transformers

Single PhaseType 1-E EncapsulatedType 1-E general purpose transformers are single phase, resin encapsulated designs suitable for indoor or outdoor applications. It’s totally enclosed, non-ventilated enclosure make it ideally suited for use in areas that contain dust, moisture, or corrosive fumes. Available in ratings through 25 KVA type 1-E transformers can be mounted in any position for indoor installations and in upright positions only for outdoor installations. Three PhaseType 3-E EncapsulatedType 3-E resin encapsulated, 3-phase transformers are available in ratings of 3-75 KVA. Its totally enclosed non-ventilated enclosure makes the 3-E ideally suited for outdoor as well as indoor locations. Type 3-E transformers utilize the 185°C insulation system with 115°C rise. 3-E transformers 3-15 KVA are T-T connected.Units installed outdoors must be mounted in upright position. 1-V general purpose transformers are single phase ventilated units designed primarily for indoor locations (also for outdoor for 600 volt class with the addition of weathershields).

The 1-V utilizes a 220°C insulation system with 150°C rise and is available in ratings of 15-167 KVA. The 3-phase 3-V ventilated dry-type is available in ratings of 15-750 KVA. Its 220°C insulation system (150°C rise) is self-extinguishing. 3-V enclosures are designed for indoor locations (or outdoors for 600 volt class with addition of weathershields). All Micron dry-type distribution and control transformers are built and tested in accordance with applicable NEMA, ANSI and IEEE standards. All 600 volt class transformers are UL listed unless otherwise noted. The Micron family of dry-type distribution transformers is seismically tested, seismically qualified, and exceeds requirements of the Uniform Building Code (UBC) and California Code Title 24. Micron standard dry-type distribution transformers are designed for 60 Hz operation. Transformers required for other frequencies must be specifically designed. Short term overload is designed into transformers as required by ANSI.

Basically, dry-type distribution transformers will deliver 200% nameplate load for one-half hour; 150% load for one-hour; and 125% load for four-hours without being damaged provided that a constant 50% load precedes and follows the overload. See ANSI C57 .96-01.250 for additional limitations. Continuous overload capacity is not deliberately designed into a transformer because the design objective is to be within the allowed winding temperature rise with nameplate loading. Insulation System & Temperature Rise Industry standards classify insulation systems and rise as shown below: The design life of transformers having different insulation systems is the same -the lower temperature systems are designed for the same life as the higher temperature systems. All Micron 600 volt class dry-type distribution transformers are designed to meet NEMA ST-20 levels listed here. *Applies to general purpose transformers only. Primary and secondary windings are terminated in the wiring compartment.