430.130 Branch-Circuit Short-Circuit and Ground-Fault Protection for Single Motor Circuits Containing Power Conversion Equipment.
Code Change Summary: A new code section provides requirements for motor installations where a variable frequency drive (VFD) is used.
In the 2011 NEC®, sections 430.52 and 430.53 provide guidelines on sizing overcurrent protective devices (OCPD’s) for motor installations based on motor type and type of OCPD used to protect the motor. This section is sufficient for electromechanical motor starting equipment but may not always be suitable when power conversion equipment, such as a VFD, is used.
New sections 430.130 and 430.131 consider the special needs of the VFD controller overcurrent protection functions. The revised text also includes an informational note that mentions where to find the required overcurrent protection rating for a VFD controller.
New section 430.130(A)(3) clarifies that self-protected combination controllers can only be used where specifically identified in the manufacturer’s instructions for the power conversion equipment or if otherwise marked on the equipment. This prevents using the large percentages of full load current mentioned in 430.52(C)(6) for adjustable trip settings unless the controller has been specifically identified in the manufacturer’s instructions for the power conversion equipment.
Below is a preview of the NEC®. See the actual NEC® text at NFPA.ORG for the complete code section. Once there, click on the “free access” tab and select the applicable year of NFPA 70 (National Electrical code).
2014 Code Language:
430.130 Branch-Circuit Short-Circuit and Ground-Fault Protection for Single Motor Circuits Containing Power Conversion Equipment.
(A) Circuits Containing Power Conversion Equipment.
Circuits containing power conversion equipment shall be protected by a branch-circuit short-circuit and ground-fault protective device in accordance with the following:
(1) The rating and type of protection shall be determined by 430.52(C)(1), (C)(3), (C)(5), or (C)(6), using the full-load current rating of the motor load as determined by 430.6.
(2) Where maximum branch-circuit short-circuit and ground-fault protective ratings are stipulated for specific device types in the manufacturer’s instructions for the power conversion equipment or are otherwise marked on the equipment, they shall not be exceeded even if higher values are permitted by 430.130(A)(1).
(3) A self-protected combination controller shall only be permitted where specifically identified in the manufacturer’s instructions for the power conversion equipment or if otherwise marked on the equipment.