You're asking a good question about disconnect requirements for a VFD-based motor control system. Here's a breakdown of considerations and why you might need more than just the rack-mounted breakers as a disconnect

Understanding the Requirements

The National Electrical Code (NEC) outlines the requirements for disconnecting means for motor circuits. The primary reason for these requirements is safety: Safety for Maintenance

Provides a way to de-energize the entire system before maintenance or troubleshooting.

Fault Protection

Allows for quick shutdown in case of a malfunction.

Analyzing Your Situation1. Individual Drive Breakers

These are good! They provide overcurrent protection (short circuit and overload) for each individual motor and VFD. They likely also provide a degree of disconnecting means.2.

Rack-Mounted Unit

The fact that the drives are rack-mounted makes it appear to be a "unit" or "system", but it's still composed of distinct motor drives.3.

Cord-and-Plug Connection

This is where the key consideration comes in. You're relying on a cord and plug for your main supply.

Why the Breakers Might Not Be Enough NEC 430.102 Location

The disconnecting means must be readily accessible and within sight of the motor, the driven machinery, and the motor controller. This is often interpreted as meaning that the disconnect should be close enough that the person operating the disconnect can clearly see the motor and controller, and the disconnect means should be within sight of the hoist location.

Service Entrance Disconnect

The breakers in the panel might meet code as long as the motor location can see the panel the breakers are in.

Why you Probably Need a Dedicated Disconnect Safety

A breaker in a panel is not ideal for immediate response during a malfunction. Having a readily accessible disconnect closer to the hoist (e.g., on or near the rack unit) provides a more convenient and safer way to kill the power in an emergency.

Maintenance

Easier and more convenient lockout/tagout (LOTO) during servicing. Going back to the main panel to lock out a breaker is less efficient and potentially less safe.

Practicality

Having a disconnect close to the hoist simplifies troubleshooting.

The Best Approach: A Lockable Disconnect at the Rack Unit

The best practice, and likely code-compliant approach, is to:1. Install a suitable disconnect switch on or immediately adjacent to the rack-mounted unit. A fused disconnect or non-fused disconnect switch is acceptable, depending on your specific design.2. Ensure the disconnect switch is lockable. This is critical for LOTO procedures.3. Ensure the disconnect switch is readily accessible.Recommendations1. Consult a Qualified Electrical Inspector

The only* way to be 100% certain is to have your installation reviewed by a local electrical inspector. They can interpret the NEC based on your specific circumstances and location.2.

Review the Contractor's Specifications

Examine the contractor's drawings and specifications closely. Do they explicitly address disconnect requirements? If not, raise the question.3.

Prioritize Safety and Convenience

Even if the local inspector says the breakers alone are technically acceptable, strongly consider the safety and convenience benefits of a dedicated disconnect. It's a relatively small cost for a significant improvement in safety and usability.

In conclusion, while the individual drive breakers provide overcurrent protection, they likely do not meet the NEC requirements for a readily accessible and lockable disconnecting means. Adding a disconnect switch near the rack unit is the recommended and safest approach. Flag for review