Article 630

Electric Welders

Part I. General

630.1 Scope. This article covers apparatus for electric arc welding, resistance welding, plasma cutting, and other similar welding and cutting process equipment that is connected to an electrical supply system.

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630.6 Listing. All welding and cutting power equipment under the scope of this article shall be listed.

Part II. Arc Welders

1. Ampacity of Supply Conductors. The ampacity of conductors for arc welders shall be in accordance with 630.11(A) and (B).
   1. Individual Welders. The ampacity of the supply conduc‐ tors shall be not less than the I 1eff value on the rating plate. Alternatively, if the I 1eff is not given, the ampacity of the supply conductors shall not be less than the current value determined by multiplying the rated primary current in amperes given on the welder rating plate by the factor shown in Table 630.11(A) based on the duty cycle of the welder.
   2. Group of Welders. Minimum conductor ampacity shall be based on the individual currents determined in 630.11(A) as the sum of 100 percent of the two largest welders, plus
   
   85 percent of the third largest welder, plus 70 percent of the fourth largest welder, plus 60 percent of all remaining welders.Exception: Percentage values lower than those given in 630.11(B) shall be permitted in cases where the work is such that a high-operating duty cycle for individual welders is impossible.Informational Note: Duty cycle considers welder loading based on the use to be made of each welder and the number of weld‐ ers supplied by the conductors that will be in use at the same time. The load value used for each welder considers both the magnitude and the duration of the load while the welder is in use.
2. Overcurrent Protection. Overcurrent protection for arc welders shall be as provided in 630.12(A) and (B). Where the values as determined by this section do not correspond to the standard ampere ratings provided in 240.6 or where the rating or setting specified results in unnecessary opening of the overcurrent device, the next higher standard rating or setting shall be permitted.
   1. For Welders. Each welder shall have overcurrent protec‐ tion rated or set at not more than 200 percent of I 1max. Alterna‐ tively, if the I 1max is not given, the overcurrent protection shall be rated or set at not more than 200 percent of the rated primary current of the welder.An overcurrent device shall not be required for a welder that has supply conductors protected by an overcurrent device rated or set at not more than 200 percent of I 1max or at the rated primary current of the welder.If the supply conductors for a welder are protected by an overcurrent device rated or set at not more than 200 percent of I 1max or at the rated primary current of the welder, a separate overcurrent device shall not be required.
   2. For Conductors. Conductors that supply one or more welders shall be protected by an overcurrent device rated or set at not more than 200 percent of the conductor ampacity.
   Informational Note: I 1max is the maximum value of the rated supply current at maximum rated output. I 1eff is the maximum value of the effective supply current, calculated from the rated supply current (I 1), the corresponding duty cycle (duty factor) (X), and the supply current at no-load (I 0) by the following equation:
   [630.12(B)]I X  I2 2 1 01  XI 1eff
   
   Table 630.11(A) Duty Cycle Multiplication Factors for Arc Welders
   Multiplier for Arc Welders
3. Disconnecting Means. A disconnecting means shall be provided in the supply circuit for each arc welder that is not equipped with a disconnect mounted as an integral part of the welder. The disconnecting means identity shall be marked in accordance with 110.22(A).Duty CycleNonmotor Generator Motor GeneratorThe disconnecting means shall be a switch or circuit breaker,1001.001.00and its rating shall be not less than that necessary to accommo‐900.950.96date overcurrent protection as specified under 630.12.800.890.91700.840.86600.780.81
4. Marking. A rating plate shall be provided for arc weld‐ ers giving the following information:
   500.710.75(1) Name of manufacturer400.630.69(2) Frequency300.550.62(3) Number of phases20 or less0.450.55(4) Primary voltage
5. ARTICLE 630 — ELECTRIC WELDERS

1. I 1max and I 1eff, or rated primary current
2. Maximum open-circuit voltage
3. Rated secondary current
4. Basis of rating, such as the duty cycle

630.15 Grounding of Welder Secondary Circuit. The secon‐ dary circuit conductors of an arc welder, consisting of the elec‐ trode conductor and the work conductor, shall not be considered as premises wiring for the purpose of applying Arti‐ cle 250.

Informational Note: Connecting welder secondary circuits to grounded objects can create parallel paths and can cause objec‐

1. Groups of Welders. The ampacity of conductors that supply two or more welders shall not be less than the sum of the value obtained in accordance with 630.31(A) for the largest welder supplied and 60 percent of the values obtained for all the other welders supplied.Informational Note: Explanation of Terms
   1. The rated primary current is the rated kilovolt-amperes (kVA) multiplied by 1000 and divided by the rated primary voltage, using values given on the nameplate.
   2. The actual primary current is the current drawn from the supply circuit during each welder operation at the partic‐tionable current over equipment grounding conductors.
      Part III. Resistance Welders630.31 Ampacity of Supply Conductors. The ampacity of the supply conductors for resistance welders shall be in accordance

ular heat tap and control setting used.

The duty cycle is the percentage of the time during which the welder is loaded. For instance, a spot welder supplied by a 60-Hz system (216,000 cycles per hour) and making 400 15-cycle welds per hour would have a duty cycle of

1. percent (400 multiplied by 15, divided by 216,000, multiplied by 100). A seam welder operating 2 cycles “on” and 2 cycles “off” would have a duty cycle of 50 percent.with 630.31(A) and (B).Informational Note: The ampacity of the supply conductors for resistance welders necessary to limit the voltage drop to a value permissible for the satisfactory performance of the welder is usually greater than that required to prevent overheating.
   1. Individual Welders. The rated ampacity for conductors for individual welders shall comply with the following:

1. The ampacity of the supply conductors for a welder that may be operated at different times at different values of primary current or duty cycle shall not be less than 70 percent of the rated primary current for seam and automatically fed welders, and 50 percent of the rated primary current for manually operated nonautomatic welders.
2. The ampacity of the supply conductors for a welder wired for a specific operation for which the actual primary current and duty cycle are known and remain unchanged shall not be less than the product of the actual primary current and the multiplier specified in Table 630.31(A)(2) for the duty cycle at which the welder will be operated.

Table 630.31(A)(2) Duty Cycle Multiplication Factors for Resistance Welders

Duty Cycle

(%) Multiplier

50 0.71

40 0.63

30 0.55

25 0.50

20 0.45

15 0.39

10 0.32

7.5 0.27

5 or less 0.22

1. Overcurrent Protection. Overcurrent protection for resistance welders shall be as provided in 630.32(A) and (B). Where the values as determined by this section do not corre‐ spond with the standard ampere ratings provided in 240.6 or where the rating or setting specified results in unnecessary opening of the overcurrent device, a higher rating or setting that does not exceed the next higher standard ampere rating shall be permitted.
   1. For Welders. Each welder shall have an overcurrent device rated or set at not more than 300 percent of the rated primary current of the welder. If the supply conductors for a welder are protected by an overcurrent device rated or set at not more than 200 percent of the rated primary current of the welder, a separate overcurrent device shall not be required.
   2. For Conductors. Conductors that supply one or more welders shall be protected by an overcurrent device rated or set at not more than 300 percent of the conductor ampacity.
2. Disconnecting Means. A switch or circuit breaker shall be provided by which each resistance welder and its control equipment can be disconnected from the supply circuit. The ampere rating of this disconnecting means shall not be less than the supply conductor ampacity determined in accordance with 630.31. The supply circuit switch shall be permitted as the welder disconnecting means where the circuit supplies only one welder.
3. Marking. A nameplate shall be provided for each resistance welder, giving the following information:

1. Name of manufacturer
2. Frequency
3. Primary voltage
4. Rated kilovolt-amperes (kVA) at 50 percent duty cycle
5. Maximum and minimum open-circuit secondary voltage
6. Short-circuit secondary current at maximum secondary voltage
7. Specified throat and gap setting

Part IV. Welding Cable

1. Conductors. Insulation of conductors intended for use in the secondary circuit of electric welders shall be flame retardant.
2. Installation. Cables shall be permitted to be installed in a dedicated cable tray as provided in 630.42(A), (B), and (C).

1. Cable Support. The cable tray shall provide support at not greater than 150-mm (6-in.) intervals.
2. Spread of Fire and Products of Combustion. The installa‐ tion shall comply with 300.21.
3. Signs. A permanent sign shall be attached to the cable tray at intervals not greater than 6.0 m (20 ft). The sign shall read as follows:

CABLE TRAY FOR WELDING CABLES ONLY