OK, it won't be easy, but these five steps will help your next transformer installation run more smoothly. Pole-mounted distribution transformer with center-tapped secondary. integrated circuits made switch. for certain installation. Sort by: File type: Displaying. Installation Effortless installation. Commissioning Easy to configure. ABB green transformer.
A transformer is a device in which two circuits are coupled by a magnetic. it is easy to drive the core into saturation for at. and some sort of optimum is. Transformer Installation. Determine Transformer Current. The neutral-to-case bond can be made at the source of a separately derived system or at the.
Transformer Installation. By Mike Holt for EC& M Magazine Installing transformers in accordance with the NEC requires.
Code requirements. Most installations. NEC challenge and transformers can extend that challenge to a new level. A properly. designed, installed and safe installation will ensure that the conductors and equipment. In addition, grounding is also an overriding issue.
So let’s get started. For this exercise, let’s assume we are installing a 4. VA and a 1. 12. 5 k. VA 4. 80. V delta primary to a 2. Y/1. 20. V 3- phase wye secondary. Each transformer.
The length of the conductors. C. Step 1. Determine Transformer Current Ratings.
Determine the primary and secondary current rating of the transformers: Primary Current Secondary Current. VA 4. 5,0. 00 VA/(4. A 4. 5,0. 00 VA/(2.
A1. 12. 5 k. VA 1. VA/(4. 80 x 1. 7.
A 1. 12,5. 00 VA/(2. AStep 2. Primary Protection [4. The primary. winding of transformers shall be protected against overcurrent in accordance with the. Table 4. 50. 3 and all applicable notes. Where 1. 25 percent of the primary. A), the next higher rating can be used [Note 1].
VA 5. 4A x 1. 2. 5 = 6. A, next size up 7. A1. 12. 5 k. VA 1. A x 1. 2. 5 = 1. 69. A, next size up 1. A Step 3. Size Primary Conductor: Feeder conductors.
Table 3. 10. 1. 6, before any ampacity adjustment. C) and 2. 15. 2(A)(1)].
VA 5. 4A x 1. 2. 5 = 6. A, 4 AWG rated 8. A at 7. 5°C, Table 3. VA 1. 35. A x 1. 2. A, 2/0 AWG rated 1. A at 7. 5°C, Table.
Sizing Equipment Grounding Conductor (when required) 2. A): The size of the equipment grounding (bonding) conductor for the transformer primary is.
VA 7. 0A Primary Protection (Step 2), Table 2. AWG1. 12. 5 k. VA 1. A Primary Protection (Step 2), Table 2. AWGStep 4. Size Secondary Conductor: Secondary. This means that the next size.
B) does not apply. Secondary overcurrent protection is not required, but overcurrent. A) and (D). Overcurrent Protection Device Size: Where a feeder supplies. A). 4. 5 k. VA 1. A x 1. 2. 5 = 1. 56.
A, 1. 75. A protection. VA 3. 12. A x 1. 2. A, 4. 00. A protection. Author’s Comment: Secondary overcurrent protection is. Since secondary overcurrent protection is provided.
Table 4. 50. 3(B) and 2. B)(3). Secondary Conductor Size: Secondary conductors must have an. Table 3. 10. 1. 6 based on 7. C terminal rating [1. C)]. This means that the next size up rule contained in 2. B) does not apply.
VA 1. 25. A x 1. 2. A, 1. 75. A protection = 2/0 AWG, rated.
A1. 12. 5 k. VA 3. A x 1. 2. 5 = 3. 90. A, 4. 00. A protection = 6. ABut…. Where the number of current- carrying conductors. Table 3. 10. 1. 5(B)(2)(a).
For our examples, there are four current- carrying conductors. B)(4)(c)], therefore the. C ampacity [1. 10. C)], must be no less.
A for the 4. 5 k. VA transformer and 4. A for the 1. 12. 5 k.
VA transformer. 4. VA 3/0 AWG, rated 2. A x 0. 8. 0 = 1. 80. A, greater than 1.
A protection. 11. VA 6. 00 kcmil, rated 4. A x 0. 8. 0 = 3. 80. A, therefore we must use the next size larger conductor. VA 7. 00 kcmil, rated 5. A x. 0. 8. 0 = 4.
A protection. Step 5. Grounding and Bonding [2. A)]. Transformer secondarys that operate at over 5.
V [2. 50. 2. 0(A) and 2. I)] must be bonded. A)(3)]. In addition, separately derived systems shall be grounded.
A)(1)]. 2. 50. 3. A)(1) Bonding – Effective Fault Current Path. To. provide the low impedance path necessary to clear a ground- fault on a separately derived. X0 Terminal). The bonding jumper. Table 2. 50. 6. 6, based on the total. VA Secondary Conductors 3/0 AWG = 4 AWG Bonding Jumper. VA Secondary Conductors 7.
AWG Bonding Jumper The neutral- to- case bond can be made at the source of a separately. When there is no secondary side disconnecting means or overcurrent. DANGER: Failure to provide a low impedance ground- fault path. The result is that all electrical. CAUTION: The neutral- to- case connection for a separately derived.
A)(1) Exception No. Such multiple neutral current. See. 2. 50. 6 and 2. A). 2. 50. 3. 0(A)(2)(a) Grounding Single Separately Derived Systems.
A grounding electrode conductor for a single separately derived system must be sized in. This conductor shall connect the grounded conductor of the derived system to. A)(4). The grounding electrode conductor. A)(1)]. 4. 5 k. VA Secondary Conductors 3/0 AWG = 4 AWG Bonding Jumper. VA Secondary Conductors 7.
AWG Bonding Jumper Author’s Comment: The grounding electrode conductor must. It cannot be terminated to. A)(4) Grounding Electrode.
The grounding electrode conductor. Effectively grounded metal member of the structure.(2) Effectively grounded metal water pipe, within 5 ft from the point of entrance into.
Exception: The grounding electrode conductor can terminate. Where an effectively grounded metal member of the building. An electrode encased by at least 2 in. AWG. See 2. 50. 5. A)(3). A ground ring encircling the building or structure, in.
AWG. See 2. 50. 5. A)(4). Rod or pipe electrodes not less than 8 ft in length. See. 2. 50. 5. 2(A)(5). A plate electrode that exposes not less than 2 sq ft of.
See 2. 50. 5. 2(A)(6)Other local metal underground systems or structures such. See 2. 50. 5. 2(A)(7). Mike Holt’s Comment: If you have any comments or feedback, please let me know, Mike@Mike.