DTX Transformers Help

Electrostatically Shielded Transformers have a single sheet of aluminum or copper foil inserted between the primary windings and the secondary windings of a transformer. The electrostatic shield (also known as a Faraday shield) prevents high-frequency electrical and electronic noise from passing on to the primary windings, from the load. Electrostatic shields are securely grounded to the core of the transformer. Eaton has had their electrostatically shielded transformers tested for performance, with the following results:

Electrostatic shielding shall provide the following minimum attenuation when tested per MIL-Std-220A, Method of Insertion Loss Measurement, with matched impedance no load technique:

a. Common mode noise attenuation: Minus 80 dBA minimum at 0.1 kHz to 1.5 kHz; minus 55 dBA minimum at 1.51 kHz to 100 kHz.

b. Normal mode (Transverse mode) noise attenuation: Minus 35dBA minimum at 1.5 kHz to 10 kHz.

Primary to Secondary Capacitance of 24.74 – 18.06 picofarads on the range 100Hz – 20kHz.

Low Temp Rise Transformers, 115°C temperature rise or 80°C rise ventilated models, or 80°C rise encapsulated models, are specially designed to have fewer winding losses (“copper” or “coil” losses) than standard transformers. This causes low temperature rise transformers to have fewer losses (therefore greater efficiencies) when the transformer is heavily loaded compared to other transformers.

Effective January 1, 2016, new U.S. Federal law 10 CFR Part 431 (2016) mandates that manufacturers of low-voltage dry-type distribution transformers cannot legally produce transformers that do not meet new minimum energy efficiency levels for installation in the U.S. or U.S. Territories. These DOE 2016 efficiency levels are shown below:

DOE 2016 10 CFR Part 431 Minimum Efficiency Levels for 600-Volt Class Dry-Type Distribution Transformers

Single-Phase*		Three-Phase
KVA	Efficiency %	KVA	Efficiency %
15	97.70	15	97.89
25	98.00	30	98.23
37.5	98.20	45	98.40
50	98.30	75	98.60
75	98.50	112.5	98.74
100	98.60	150	98.83
167	98.70	225	98.94
250	98.80	300	99.02
333	98.90	500	99.14
---	---	750	99.23
---	---	1000	99.28

*Note: Single-phase efficiency levels did not change in 2016; they are the same as the 2007 (NEMA TP-1) efficiency levels.

NEMA TP-1 Energy Efficient Transformers are required to meet minimum efficiency levels at 35% of their full load capacity. NEMA determined TP-1 efficiency levels in conjunction with the United States Department of Energy and 10 CFR Part 431 (2007). US Federal laws require that distribution transformers installed in the United States have a minimum efficiency equal to NEMA TP-1 values. CSA Standard C802.2-00 for energy efficiency requires efficiency levels identical to those in NEMA Standard TP-1. NEMA TP-1 efficiency levels are identified in the following Table. Effective January 1, 2016, the U.S. Dept.... of Energy has mandated that low-voltage dry-type distribution transformers meet a higher efficiency level than “TP-1” efficiencies. These new efficiencies are codified in 10 CFR Part 431 (2016).

NEMA Premium® Efficient Transformers have 30% fewer losses than NEMA TP-1 efficient transformers, measured at 35% of their full load capacity. The NEMA Premium® Efficiency Transformer Program is a voluntary program that manufacturers may participate in. NEMA Premium® efficiency levels are identified in the following Table. NEMA Premium efficient transformers do not meet the new federally-mandated efficiencies effective January 1, 2016.

CSL3 Efficient Transformers are even more efficient than NEMA TP-1 rated transformers. They are named after the U.S. Dept. of Energy Candidate Standard Level 3. In comparison, NEMA TP-1 transformers are CSL1. CSL3 or “E3” Eaton transformers are currently available in rating of K-13, 115ºC or 150ºC, with copper windings. A typical style number is N48M28F75CUE3. CSL3 efficient transformers have roughly 30% fewer losses than NEMA TP-1 models. CSL3 (E3) transformer efficiencies are listed in the following Table.

Drive Isolation Transformers, or Motor Drive Isolation transformers, are specially designed for use with AC and dc adjustable speed drives. They are designed to withstand the mechanical stresses of current reversals and short circuits associated with SCR drives.

Mini-Power Centers combine three components in to a single assembly; load center, transformer, and primary main circuit breaker. Combining these components in to a single enclosure reduces the wall space required for installation. It also reduces the amount of time required to complete the installation compared to installing the components separately.

Totally Enclosed Non-Ventilated transformers are NEMA 3R rated transformers. TENV enclosures are similar in construction to that of standard ventilated enclosures, except TENV enclosures do not have any openings in the enclosure. Because there are no openings for air to circulate through the transformer to provide cooling, TENV models are much larger in size than a ventilated transformer with equivalent electrical characteristics. Selection of a standard NEMA 2 ventilated transformer and field-installed weather shields is a more cost-effective solution if the particular application permits this.

Class 1 Division 2 Groups A, B, C & D transformers are suitable for installation in hazardous locations. Class 1 Division 2 Groups A, B, C & D environments are defined by the National Electrical Code in Section 501. When installed per NEC Section 500, these transformers do not provide a source of ignition. All electrical components are sealed and not accessible by these gases or vapors.

Open Type Core and Coil Assemblies are typically used by OEM customers who are installing ventilated transformers in a customer-provided enclosure. They do not need the protection offered by our enclosure.

Low Sound transformers are commonly specified by customers who are going to install a transformer in an area where the natural sound emitted by a transformer may be objectionable. NEMA Standard ST-20 mandates the maximum allowed audible sound level for transformers. (Link to the NEMA ST-20 Sound Level table below). Typical low sound requirements are –3dB and –5dB.

Marine Duty transformers are commonly used in marinas and other docking facilities, dry-docks, and on-board non-combat shipping vessels. Marine duty transformers on vessels are installed below deck where there is an elevated ambient temperature. Marine duty transformers are designed to operate in an elevated ambient of 50°C. Eaton’s family of marine duty transformers are design approved by the American Bureau of Shipping (ABS) and have the ABS logo on their nameplates. ABS requires qualifying transformers to be copper-wound, and a maximum of 140°C temperature rise. Eaton offers 115°C rise as standard.

Buck-Boost transformers are used to slightly increase (boost) or slightly decrease (buck) the available voltage. When wired in buck-boost arrangements, these transformers are autotransformers; you can get significantly greater output current than the nameplate kVA of the transformer(s) because the primary and secondary windings are connected together.

When connected at their nameplate voltages, “buck-boost” transformers are ideally suited for low voltage applications, such as low voltage lighting and landscape lighting.

Harmonic Mitigating Transformers actually treat harmonics in three-phase electrical distribution systems. Type NON (0-deg phase shift) can be deployed on their own to treat 3rd and other triplen (9th, 15th, 21st, 27th, etc) harmonic currents that are the signature of single-phase non-linear loads such as personal computers. The 30-degree phase shift created between pairs of Type NON and Type THR transformers, or pairs of Type NEG and Type POS transformers is used to treat 5th, 7th, 17th, and 19th harmonics which are typical of three-phase non-linear loads such as drives. Coordinated pairs of HMTs with a 30-degree phase shift between them also treat triplen harmonics.

It is common to coordinate Type NON HMTs with standard delta-wye transformers (30-deg phase shift) or energy efficient transformers to facilitate harmonic treatment in K-12 schools and universities. Loads which contain triplen harmonics are connected to the HMT and the remaining loads are connected to the energy efficient transformer. This scheme provides the benefits of triplen harmonic treatment (at the HMT); 5th, 7th, 17th, 19th, etc harmonic treatment (due to the 30-deg phase shift between the HMT and energy efficient transformer); and energy savings (via use of the energy efficient transformers).

OPEN enclosure type is an option for ventilated transformers. OPEN transformers do not have any enclosure around them. Open core and coil assemblies are commonly required by OEM customers who are installing the transformer inside one of their enclosures, so the protection provided by our enclosure is not required.

NEMA 2 enclosures are the standard construction of Eaton Corporation's ventilated transformers. WEATHERSHIELDS can be field-installed to convert a standard NEMA 2 enclosure to a NEMA 3R enclosure. Field-installed WEATHERSHIELDS are included in the ACCESSORIES button in the lower right-hand corner of the GENERAL TAB. The purchase price of a standard NEMA 2 ventilated transformer and weathershields is significantly less than buying a NEMA 3R rated encapsulated or totally enclosed non-ventilated transformer.

NEMA 3R Encaps enclosure: A NEMA 3R enclosure is the standard construction of encapsulated transformers.

NEMA 3R TENV enclosure: Ventilated designs may be ordered with a special Totally Enclosed Non-Ventilated (TENV) enclosure that has a NEMA 3R rating. TENV enclosed transformers are significantly larger and more expensive than ventilated transformers with field-installed weathershields.

NEMA 4X Stainless Steel enclosure: Encapsulated designs may be ordered with a special NEMA 4X enclosure. The enclosure will be manufactured using Stainless Steel grade 304 or grade 316L. This enclosure type is not available on ventilated designs.

150°C temperature rise is standard for ventilated transformers. 115°C or 80°C temperature rise are available as options on ventilated transformers at additional cost.

115°C temperature rise is standard for encapsulated transformers and mini-power centers. 80°C temperature rise is available as an option on encapsulated transformers at additional cost.

NEMA Standard ST-20 defines the maximum audible sound level of transformers. The sound level is based upon the kVA rating of the transformer, and is independent of the type of transformer (K-factor, NEMA TP-1, Drive Isolation, Low Temperature Rise, etc.). The sound levels specified in NEMA ST-20 are taken under ideal conditions in soundproof chambers. The field-measured audible sound level of a transformer is typically 6-10dB greater than the sound level measured under the ideal conditions outlined in NEMA ST-20. The following table lists the NEMA ST-20 sound levels for dry-type distribution transformers.

Mini-Power Centers (MPC) are provided as standard with primary main circuit breakers having an interrupting rating of 14K AIC. Optional primary main circuit breakers with higher AIC ratings are available as a standard option. The following Table shows the available primary main circuit breakers and their corresponding AIC rating.

LKS1: Typically used for single-phase transformers rated 15 kVA to 37.5 kVA, and three-phase transformers rated 15 kVA to 45 kVA. Kit consists of the following mechanical lugs; 8 lugs suitable for #14 - #2 gauge cable, and 4 lugs suitable for #6 - #250MCM cable. Kit includes 8 bolts, 1/4-40 X 3/4".

LKS2: Typically used for single-phase transformers rated 50 kVA to 75 kVA, and three-phase transformers rated 75 kVA to 112.5 kVA. Kit consists of the following mechanical lugs; 12 lugs suitable for #6 - #250MCM cable. Kit includes 8 bolts 1/4-20 X 3/4" and 8 bolts 1/4-20 X 1-3/4".

LKS3: Typically used for single-phase transformers rated 100 kVA to 167 kVA, and three-phase transformers rated 150 kVA to 300 kVA. Kit consists of the following mechanical lugs; 3 lugs suitable for #6 - #250MCM cable, and 22 lugs suitable for #2 - #600MCM cable. Kit includes 3 bolts 1/4-20 X 3/4" and 16 bolts 3/8-16 X 2".

LKS4: Typically used for three-phase transformers rated 500 kVA. Kit consists of the following mechanical lugs; 29 lugs suitable for #2 - #600MCM cable. Kit includes 18 bolts 3/8-16 X 2"

This option is available on all three-phase ventilated transformers, including K-factor and Harmonic Mitigating models. When selected, an Eaton Innovative Technologies model EQX series Surge Protection Device (SPD, formerly known as a TVSS) will be installed in the wiring compartment of the transformer. If visual indication that the SPD is operating is required, select the "SPD Indicating Light" option. Appropriate over current protection is provided in the circuit of the factory-installed SPD.

This option is available on three-phase ventilated transformers rated 75 kVA and below, and single-phase transformers rated 50 kVA and below. Transformers with the Easy Install feature are shipped without a pallet. This eliminates the need for the installing contractor to "rock" the transformer off of a pallet before setting the transformer in place. One person can move the transformer, set it in place, and bolt it to the floor. The mounting holes are outside the envelope of the transformer enclosure, eliminating the need to unpack the transformer and remove the front and back panels to secure the transformer to the floor. The pallet-less shipping method reduces the amount of material to be disposed.

Eaton's Juarez-manufactured distribution transformers generally do not meet the requirements set forth in the Buy American Act or ARRA.. When compliance with the Buy American Act (BAA) or ARRA is required by the specification, it is critical to completely read the specification. Specifications often include conditions that do permit Juarez-manufactured transformers to be provided on the project. Statements to look for are "Products included in the GSA procurement schedule are exempt from these requirements," or "Construction products manufactured in NAFTA countries are exempt for these requirements." Also, if the total construction contract for a project is in excess of $8,422,165.00, the Buy American Act and ARRA permit the use of NAFTA-manufactured products. This dollar amount is the total of all construction at a project, not just the electrical portion.

NEMA ST-20-2014 Average Sound Level in dB
	Self-Cooled Ventilated			Self-Cooled Sealed
	A	B	C	D
Equivalent	K-factor=1		Forced Air
Winding	K-factor=4	K-factor=13	when Fans
kVA Range	K-factor=9	K-factor=20	Running	Encapsulated
3.00 and below	40	40	67	45
3.01 to 9.00	40	40	67	45
9.01 to 15.00	45	45	67	50
15.01 to 30.00	45	45	67	50
30.01 to 50.00	45	48	67	50
50.01 to 75.00	50	53	67	55
75.01 to 112.50	50	53	67	55
112.51 to 150.00	50	53	67	55
150.01 to 225.00	55	58	67	57
225.01 to 300.00	55	58	67	57
300.01 to 500.00	60	63	67	59
500.01 to 700.00	62	65	67	61
700.01 to 1000.00	64	67	67	63
Greater than 1000	Consult Factory

Mini-Power Center Primary Main Circuit Breaker Available Ratings

Circuit Breaker Type	480 Volt AIC Rating	600 Volt AIC Rating
EHD (Standard on 480V)	14K AIC	na
FDB (Standard on 600V)	na	14K AIC
FD	25K AIC	18K AIC
HFD	65K AIC	25K AIC
FDC	100K AIC	35K AIC

NEMA TP-1 Minimum Efficiency Levels for 600-Volt Class Dry-Type Distribution Transformers (DTDT)

Single-Phase		Three-Phase
KVA	Efficiency	KVA	Efficiency
15	97.7	15	97.0
25	98.0	30	97.5
37.5	98.2	45	97.7
50	98.3	75	98.0
75	98.5	112.5	98.2
100	98.6	150	98.3
167	98.7	225	98.5
250	98.8	300	98.6
333	98.9	500	98.7
---	---	750	98.8
---	---	1000	98.9

NEMA Premium® Minimum Efficiency Levels for 600-Volt Class Dry-Type Distribution Transformers

Single-Phase		Three-Phase
KVA	Efficiency	KVA	Efficiency
15	98.39	15	97.90
25	98.60	30	98.25
37.5	98.74	45	98.39
50	98.81	75	98.60
75	98.95	112.5	98.74
100	99.02	150	98.81
167	99.09	225	98.95
---	---	300	99.02
---	---	500	99.09
---	---	750	99.16
---	---	1000	99.23

CSL3 (2007) Minimum Efficiency Levels for 600-Volt Class Dry-Type Distribution Transformers

Three-Phase
KVA	Efficiency
15	97.97
30	98.29
45	98.45
75	98.64
112.5	98.77
150	98.86
225	98.97
300	99.04
500	99.16
750	99.24
1000	99.29