Looking for low voltage transformer solutions?

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1 Looking for low voltage transformer solutions? Select the best from the industry leader. Square D Low Voltage Dry Type Transformers Make the most of your energy SM

2 Special Transformers This application guide is designed to provide a handy pocket reference for those who need to select and apply dry-type transformers in the course of their vocation. The information is also of use in all electrical work. Because it is a pocket guide, the information is brief and abbreviated. Schneider Electric will build most special dry type transformers your application requires. Your Square D field sales representatives, or transformer headquarters, will be happy to assist you in selecting the proper transformer. Data required to help you is: kva or load amperage, primary voltage, secondary or load voltage, phase, frequency, taps, insulation class and temperature rise, type of enclosure, sound level, physical limitations accessories required. Transformers available from your distributor s stock Single Phase s Voltage: 2 x 480-1/2 Ratings: kVA Voltage: 480-1/2 Ratings: 3-kVA Voltage: 600-1/2 Ratings: kVA Three Phase s Voltage: Ratings: Voltage: Ratings: Voltage: Ratings: 480r-280Y/1 3-0kVA 480r-2r with 1V center trap kVA 600r-280Y/1 6-kVA Buck and Boost (Single Phase) Voltage: 1 x 2-12/24 or 16/32; 2 x /48 Ratings:.050-3kVA Full Current in Amperes Single Phase Low Voltage Dry Type Transformers Rated Line-to-Line Voltage kva Formula: Single Phase kva Volts x Amperes/0 Three Phase Low Voltage Dry Type Transformers Rated Line-to-Line Voltage kva Formula: Three Phase kva Volts x Amperes x 1.73/0 2 3

3 The following tables have been reproduced through the courtesy of the National Fire Protection Association from the National Electric Code 08 Edition. Table Allowable Amapacities of Insulated Conductors Rated 0 Through 00 Volts, 60 C Through 90 C (1 F Through 194 F), Not More Than Three Current-Carrying Conductors in Raceway, Cable, or Earth (Directly Buried), Based on Ambient Temperature of C (86 F) Size Temperature Rating of Conductor (See Table (A).) Size AWG or kemil * 12* 10* /0 2/0 3/0 4/ Ambient Temp. ( C) 60 C (1 F) TW, UF C (167 F) RHW, THW, THWN, USE, ZW Copper C (194 F) TBS, SA, SIS, FEP, FEPB, MI, RHH, RHW-2, THHN, THW-2, THWN-2, USE-2, XHH, XHHW-2, ZW C (1 F) TW, UF C (167 F) RHW, THW, THWN, USE 90 C (194 F) TBS, SA, SIS, THHN, THW-2, THWN-2, RHH, RHW-2, USE-2, XHH, XHHW-2, ZW-2 Aluminum or Copper-Clad Aluminum Correction Factors For ambient temperatures other than C (86 F), multiply the allowable ampacities shown above by the appropriate factor shown below AWG or kemil 12* 10* /0 2/0 3/0 4/ Ambient Temp. ( F) * See 2.4(D) 08 NEC. Table 450.3(B) Maximum Rating or Setting of Overcurrent Protection for Transformers 600 Volts and Less (as a Percentage of Transformer-Rated Current) Protection Method Primary only protection Primary and secondary protection Currents of or More 1% (See Note 1.) 0% (See Note 3.) Primary Protection Currents Less Than Currents Less Than 2 Amperes Secondary Protection (See Note 2.) Currents of or More Currents Less Than 167% 0% Not required Not required 0% (See Note 3.) 0% (See Note 3.) 1% (See Note 1.) NOTES: 1. Where 1 percent of this current does not correspond to a standard rating of 167% a fuse or nonadjustable circuit breaker, a higher rating that does not exceed the next higher standard rating shall be permitted. 2. Where secondary overcurrent protection is required, the secondary overcurrent device shall be permitted to consist of not more than six circuit breakers or six sets of fuses grouped in one location. Where multiple overcurrent devices are utilized, the total of all the device ratings shall not exceed the allowed value of a single overcurrent device. If both breakers and fuses are utilized as the overcurrent device, the total of the device ratings shall not exceed that allowed for fuses. 3. A transformer equipped with coordinated thermal overload protection by the manufacturer and arranged to interrupt the primary current shall be permitted to have primary overcurrent protection rated or set at a current value that is not more than six times the rated current of the transformer for transformers having not more than 6 percent impedance and not more than four times the rated current of the transformer for transformers having more than 6 percent but not more than 10 percent impedance. NEMA TP 1-02 NEMA Class I Efficiency Levels for Dry Type Distribution Transformers Low Voltage Reference Condition: C and 35% Single Phase Three Phase kva % Efficiency kva % Efficiency Sound Levels Square D Dry Type Transformers are the quietest available, whether standard or special sound level limits are ordered. Testing is done in accordance with NEMA standards. Sound Levels 600 Volts and Below NEMA Standard Sound kva Levels 09 db db db db 0 60 db db db NOTE: Lower sound levels than those shown above are available at a slight additional charge. 4 5

4 Buck and Boost The nameplate rating on buck and boost transformers indicates the load they will handle as an isolation transformer. (Pri. 1 x 2, Sec. 12/24*, Ex.: A 1kVA buck and boost will reduce 1 or 2V to 12 or 24V and be able to carry a continuous load of 1kVA.) The majority of buck and boost transformers sold, however, are used to boost 8V to either 2V or 2V, or buck these voltages down to 8V. To use these transformers in this way, the primary and secondary windings are connected to form an auto transformer as follows: Single Phase Connect H2 to H3 X1 to H4 X2 to X3 Connect 8V to H1 and H4-X1 Connect 2V or 2V to H1 and X4 Buck/Boost Secondary kva Capacity /24 10 x nameplate rating / x nameplate rating Three Phase, Open Delta Power-s Only (Use 2 s) Connect On each unit X3 to X2 X1 to H4 H3 to H2 Then connect H1 s from each unit. Connect 8V to X1-H4, H1-H1, H4-X1 Connect 2V or 2V to X4, H1-H1, X4 X4 H1 H2 H3 H4 X1 X2 X3 X4 2 V or 2 V NOTE: This connection for power loads only. Three phase lighting loads require (3) transformers and source neutral must be carried through to load. X3 X2 X1 H4 H3 H2 H1 H1 H2 H3 H4 X1 X2 X3 X4 2 V 2 V Single phase connections Note: Non-standard ratings increase to next larger standard. Single Phase 2 x 480 to 1/2V Primary Connections 2V Service 2 V Line H1 H3 H2 H4 Connect H1 & H3 Connect H2 & H4 Connect lines to H1-H3 & H2-H4 Secondary Connections 1V 2-Wire Circuit X1 X2 X3 1 V Connect X1 & X3 Connect X2 & X4 Connect to X1-X3 & X2-X4 X4 1/2V 3-Wire Circuit 480V Service 480 V Line H1 H3 H2 H4 Connect H3 & H2 Connect H1 & H4 Connect lines to H1 & H4 2V 2-Wire Circuit 2 V Connect X3 & X2 Connect to X1 & X4 2 V or 2 V Three Phase kva Rating Buck/Boost Secondary kva Capacity /24 nameplate kva x 1.73 x /32 nameplate kva x 1.73 x 7.5 NOTE: When used as an auto transformer, the buck and boost unit will carry greater loads than shown on the nameplate. For other uses and connections, ask your distributor for a copy of the Product Data Bulletin (7414SP9901) or a Buck-Boost Slide Rule or use the online calculator. Visit and search for Buck and Boost. Check local codes relative to the use of auto transformers before applying buck and boost transformers. 1 V 1 V 2 V The junction of X3-X2 may be used as the neutral of a 3-wire system and must be bonded to the nearest earth ground per NEC requirements. 6 7

5 Note: Non-standard ratings increase to next larger standard. The following diagrams show special ways that standard 2 x 480-1/2 single phase transformers can be connected for special applications. LV LV Single Unit Connected 2 V H1 H3 H2 H4 as Auto Transformer 2V to 480V kva Capacity 480 V 2 x Nameplate kva HV HV kva 2 Single Unit Connected as Auto Transformer 480V to 600V kva Capacity 5 x Nameplate kva kva 5 kva Rating of Transformer Required kva Rating of Transformer Required Two unit transformers connected in Hoppy Hookup for single phase lighting and single phase power loads from three phase supply. This connection allows changeover of existing single phase service to three phase service without changing existing lighting panels or secondary neutrals. The neutral current will be the same as with the original single phase service rather than increasing by the factor of 1.73 ( 3 ). H1 H3 H2 H4 H1 H3 H2 H4 1 V 1 V * NOTE: The primary common current will be the in the other two lines. 3 x the current For 480V Primary Connect H2 to H3 in Each Unit For 2V Primary Connect H3 to H1 and H2 to H4 in Each Unit Secondary kva Capacity Total Nameplate kva of Both Transformers * Secondary voltage is 1/8V, 3-wire only. NOT 1/2V, 3-wire. Three Phase Connections Note: For non-standard kva ratings increase to next larger standard kva, using single phase 2 x 480 to 1/2. Three Units Connected Delta-Wye, for Three Phase Operation H1 H3 H2 H4 H1 H3 H2 H4 H1 H3 H2 H4 Neutral For 480V Delta Primary Connect H3 to H2 in For 2V Delta Primary Connect H3 to H1 and H2 to H4 in For 416Y/2V Secondary Connect X3 to X2 in For 8Y/1V Secondary Connect X3 to X1 and X2 to X4 in Three Phase kva Capacity Total kva of Three Units Three Units Connected Delta-Delta, for Three Phase Operation H1 H3 H2 H4 H1 H3 H2 H4 H1 H3 H2 H4 For 480V Delta Primary Connect H3 to H2 in For 2V Delta Primary Connect H3 to H1 and H2 to H4 in For 2V Delta Secondary Connect X3 to X2 in For 1V Delta Secondary Connect X3 to X1 and X2 to X4 in Three Phase kva Capacity Total kva of Three Units Two Units Connected Open-Delta, for Three Phase Operation H1 H3 H2 H4 H1 H3 H2 H4 For 480V Delta Primary Connect H3 to H2 in For 2V Delta Primary Connect H3 to H1 and H2 to H4 in For 2V Delta Secondary Connect X3 to X2 in For 1V Delta Secondary Connect X3 to X1 and X2 to X4 in Three Phase kva Capacity Total kva of Two Units x 0.86 kva

6 Note: For non-standard kva ratings increase to next larger standard kva, using single phase 2 x 480 to 1/2. Two Units Connected as Open Delta Auto Transformer for Three Phase Operation for 2480; 4802 Three Phase kva Capacity (Total kva of Both Units x 2) x.86 HV HV HV H1 H3 H2 H4 H4 H2 H3 H1 X4 X2 X3 X1 LV LV LV kva 3.44 Two Units Connected as Open-Delta Auto Transformer for Three Phase Operation for ; ; ; kva Capacity ; kva 8.6 kva Capacity ; kva 6.88 The following diagram shows special ways that standard 600-1/2 single phase transformers can be connected for special applications. Two Units Connected as Open-Delta Auto Transformer for Three Phase Operation for 5480 or kva kva

7 Energy Efficient Transformers Square D general purpose and lighting transformers are known as the industry standard. Harmonic Mitigating and Non-Linear Transformers Schneider Electric expertise in power management is evident with the broad line of transformers for non-linear loads. Control Power Transformers Schneider Electric s complete line of control power transformers offer a variety of options for panel builders and OEMs. Schneider Electric North American Operating Division 1415 S. Roselle Road Palatine, IL Tel: Fax: HO9501R6/ Schneider Electric. All rights reserved.