Example No. D10 Feeder Ampacity Determination for Adjustable-Speed Drive Control [See 215.2, 430.24, 620.13, 620.14, 620.61, Tables 430.22(E), and 620.14]
Determine the conductor ampacity for a 460-volt, 3-phase, 60 Hz ac feeder supplying a group of six identical elevators. The system is adjustable-speed SCR dc drive. The power transformers are external to the drive (motor controller) cabinet. Each elevator has a separate motion/operation controller connected to the load side of the main line disconnect switch rated 10 amperes continuous to operate microprocessors, relays, power supplies, and the elevator car door operator. Each transformer is rated 95 kVA with an efficiency of 90 percent.
Conductor Ampacity
Conductor ampacity is determined as follows:
(a) Calculate the nameplate rating of the transformer:
(b) Per 620.13(D), for six elevators, the total conductor ampacity is the sum of all the currents: 6 elevators x 133 amperes = 798 amperes.
(c) Per 620.14 and Table 620.14, the conductor (feeder) ampacity would be permitted to be reduced by the use of a demand factor. Constant loads are not included. (See 620.13, FPN No. 2). For six elevators, the demand factor is 0.79. Therefore feeder diverse ampacity = 0.79 x 798 amps = 630 amperes.
(d) Per 430.24 and 215.3, the controller continuous current is 125% x 10 amperes = 12.5 amperes.
(e) The total feeder ampacity is the sum of the diverse current and all the controller constant current. I total = 630 + (6 elevators x 12.5) = 705 amperes.
(f) This ampacity would be permitted to be used to select the wire size.
See Figure D10.
Figure D10. Adjustable speed drive control
Article 90 Introduction
General
Wiring and Protection
- Article 200 Use and Identification of Grounded Conductors
- Article 210 Branch Circuits
- Article 215 Feeders
- Article 220 Branch-Circuit, Feeder, and Service Calculations
- Article 225 Outside Branch Circuits and Feeders
- Article 230 Services
- Article 240 Overcurrent Protection
- Article 250 Grounding and Bonding
- Article 280 Surge Arresters
- Article 285 Transient Voltage Surge Suppressors (TVSSs)
Wiring Methods and Materials
- Article 300: Wiring Methods
- Article 310 Conductors for General Wiring
- Article 312 Cabinets, Cutout Boxes, and Meter Socket Enclosures
- Article 314 Outlet, Device, Pull, and Junction Boxes; Conduit Bodies; Fittings; and Handhole Enclosures
- Article 320 Armored Cable Type AC
- Article 322 Flat Cable Assemblies Type FC
- Article 324 Flat Conductor Cable Type FCC
- Article 326 Integrated Gas Spacer Cable Type IGS
- Article 328 Medium-Voltage Cable Type MV
- Article 330 Metal-Clad Cable Type MC
- Article 332 Mineral-Insulated, Metal-Sheathed Cable Type MI
- Article 334 Nonmetallic-Sheathed Cable Types NM, NMC, and NMS
- Article 336 Power and Control Tray Cable Type TC
- Article 338 Service-Entrance Cable Types SE and USE
- Article 340 Underground Feeder and Branch-Circuit Cable Type UF
- Article 342 Intermediate Metal Conduit Type IMC
- Article 344 Rigid Metal Conduit Type RMC
- Article 348 Flexible Metal Conduit Type FMC
- Article 350 Liquidtight Flexible Metal Conduit Type LFMC
- Article 352 Rigid Nonmetallic Conduit Type RNC
- Article 353 High Density Polyethylene Conduit Type HDPE Conduit
- Article 354 Nonmetallic Underground Conduit with Conductors Type NUCC
- Article 356 Liquidtight Flexible Nonmetallic Conduit Type LFNC
- Article 358 Electrical Metallic Tubing Type EMT
- Article 360 Flexible Metallic Tubing Type FMT
- Article 362 Electrical Nonmetallic Tubing Type ENT
- Article 366 Auxiliary Gutters
- Article 374 Cellular Metal Floor Raceways
- Article 382 Nonmetallic Extensions
- Article 384 Strut-Type Channel Raceway
- Article 386 Surface Metal Raceways
- Article 388 Surface Nonmetallic Raceways
- Article 390 Underfloor Raceways
- Article 392 Cable Trays
- Article 394 Concealed Knob-and-Tube Wiring
- Article 396 Messenger Supported Wiring
- Article 398 Open Wiring on Insulators
Equipment for General Use
- Article 400: Flexible Cords and Cables
- Article 402: Fixture Wires
- Article 404: Switches
- Article 406: Receptacles, Cord Connectors, and Attachment Plugs (Caps)
- Article 408: Switchboards and Panelboards
- Article 409: Industrial Control Panels
- Article 410: Luminaires (Lighting Fixtures), Lampholders, and Lamps
- Article 411: Lighting Systems Operating at 30 Volts or Less
- Article 422: Appliances
- Article 424: Fixed Electric Space Heating Equipment
- Article 426: Fixed Outdoor Electric De-Icing and Snow-Melting Equipment
- Article 427: Fixed Electric Heating Equipment for Pipelines and Vessels
- Article 430: Motors, Motor Circuits, and Controllers
- Article 440: Air Conditioning and Refrigerating Equipment
Special Occupancies
- Article 500 Hazardous (Classified) Locations, Classes I, II, and III, Divisions 1 and 2
- Article 501 Class I Locations
- Article 502 Class II Locations
- Article 503 Class III Locations
- Article 504 Intrinsically Safe Systems
Special Equipment
Special Conditions
- Article 700 Emergency Systems
- Article 701 Legally Required Standby Systems
- Article 702 Optional Standby Systems
Tables
- Tables
- Notes to Tables
- Tables 11(A) and 11(B)
- Notes for Tables 11(A) and 11(B)
- Tables 12(A) and 12(B)
- Notes for Tables 12(A) and 12(B)
Annex C. Conduit and Tubing Fill Tables for Conductors and Fixture Wires of the Same Size
Annex D. Examples
- Annex D. Examples
- Example No. D1(a) One-Family Dwelling
- Example No. D1(b) One-Family Dwelling
- Example No. D2(a) Optional Calculation for One-Family Dwelling Heating Larger than Air Conditioning [See Section 220.82]
- Example No. D2(b) Optional Calculation for One-Family Dwelling, Air Conditioning Larger than Heating [See 220.82(A) and 220.82(C)]
- Example No. D2(c) Optional Calculation for One-Family Dwelling with Heat Pump(Single-Phase, 240/120-Volt Service) (See 220.82)
- Example No. D3 Store Building
- Example D3(a) Industrial Feeders in a Common Raceway
- Example No. D4(a) Multifamily Dwelling
- Example No. D4(b) Optional Calculation for Multifamily Dwelling
- Example No. D5(a) Multifamily Dwelling Served at 208Y/120 Volts, Three Phase
- Example No. D5(b) Optional Calculation for Multifamily Dwelling Served at 208Y/120 Volts, Three Phase
- Example No. D6 Maximum Demand for Range Loads
- Example No. D8 Motor Circuit Conductors, Overload Protection, and Short-Circuit and Ground-Fault Protection
- Example No. D9 Feeder Ampacity Determination for Generator Field Control
- Example No. D10 Feeder Ampacity Determination for Adjustable-Speed Drive Control [See 215.2, 430.24, 620.13, 620.14, 620.61, Tables 430.22(E), and 620.14]
- Example No. D11 Mobile Home (See 550.18)
- Example No. D12 Park Trailer (See 552.47)
Annex E. Types of Construction
EAN: 2147483647
Pages: 120
