A perennial question in planning an industrial panel with multiple devices, including a variable frequency AC drive for the main spindle motor:
NFPA 79 section 7.2.10.1 says "Each motor controller and its associated wiring shall be protected as an individual branch circuit by a short-circuit
protective device (SCPD) as specified by the controller manufacturer.
The maximum rating of the designated SCPD shall be as shown in Table 7.2.10.1." [which goes on to list the percentage of FLC you may use with various classes of fuse or types of circuit breaker].
For purposes of this requirement, is a VFD a "motor controller"? As such, must it have a dedicated set of branch-rated fuses or UL489 breaker?
In this particular case, the VFD manufacturer specifies a (maximum) 225A MCCB, but I am planning to use a 200A MCCB as the main breaker/disconnect for the panel. I am confident that the VFD, plus the handful of smaller loads on the panel, will not exceed 200A. Besides, the customer only has a 200A service available.
It seems like the 200A main breaker should be sufficient to protect the VFD; yet the above NFPA79 paragraph suggests the drive needs to be "individually" protected.
Any thoughts or experiences on this subject?
NFPA 79 section 7.2.10.1 says "Each motor controller and its associated wiring shall be protected as an individual branch circuit by a short-circuit
protective device (SCPD) as specified by the controller manufacturer.
The maximum rating of the designated SCPD shall be as shown in Table 7.2.10.1." [which goes on to list the percentage of FLC you may use with various classes of fuse or types of circuit breaker].
For purposes of this requirement, is a VFD a "motor controller"? As such, must it have a dedicated set of branch-rated fuses or UL489 breaker?
In this particular case, the VFD manufacturer specifies a (maximum) 225A MCCB, but I am planning to use a 200A MCCB as the main breaker/disconnect for the panel. I am confident that the VFD, plus the handful of smaller loads on the panel, will not exceed 200A. Besides, the customer only has a 200A service available.
It seems like the 200A main breaker should be sufficient to protect the VFD; yet the above NFPA79 paragraph suggests the drive needs to be "individually" protected.
Any thoughts or experiences on this subject?