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.

FPN: / lmax is the maximum value of the rated supply cur- rent at maximum rated output. 7 lcff is the maximum value of the effective supply current, calculated from the rated supply current (/,), the corresponding duty cycle (duty factor) (X), and the supply current at no-load (/ 0) by the following formula:

630.13 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 shall be a switch or circuit breaker, and its rating shall be not less than that necessary to accommodate overcurrent protection as specified under 630.12.

630.14 Marking. A rating plate shall be provided for arc welders giving the following information:

(1) Name of manufacturer

(2) Frequency

(3) Number of phases

(4) Primary voltage

(8) Basis of rating, such as the duty cycle

purpose of applying Article 250.
FPN: Connecting welder secondary circuits to grounded objects can create parallel paths and can cause objectionable current over equipment grounding conductors.

III. Resistance Welders

630.31 Ampacity of Supply Conductors. The ampacity

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.
FPN: 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
of the supply conductors for resistance welders
the nameplate.

(2)

ary current is the current drawn

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 as covered in 630.31(A) and (B).

(A) Individual Welders. The rated ampacity for conduc tors 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 nonauto-matic 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.

(B) Groups of Welders. The ampacity of conductors that supply two or more welders shall not be less than the sum

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

Resistance Welders

Duty Cycle

(%) Multiplier

50 0.71
40 0.63
30 0.55
The actual prim
from the supply circuit during each welder
operation at the particular heat tap and control
setting