ZEEYI ELECTRIC / Switching logic explained
BBM vs MBB
load break switches.
Understand the transition terminology before reviewing a four-position sectionalizing switch.
Updated · ZEEYI ELECTRIC
The terms describe a transition, rather than the number of stable switch positions. The correct choice follows the system’s approved connection sequence.
The distinction at a glance.
| REVIEW POINT | BBM | MBB |
|---|---|---|
| Full name | Break-before-make | Make-before-break |
| Connection transition | Existing path opens first. | Next path closes first. |
| Continuity consideration | A transition interruption may occur. | Connection overlap may maintain continuity in a suitable design. |
| What to verify | Approved sequence and acceptable interruption. | Approved sequence and suitability of overlapping connections. |
Conceptual comparison only. Exact connections and transition behavior depend on the selected switch design and circuit.
Selection / Four-position family
Specify the diagram.
Not just the acronym.
A request for a four-position switch should identify the connections at each stable position and the intended transitions. The labels BBM and MBB alone do not define every position or establish compatibility between part numbers.
Send the circuit or position diagram with the inquiry and ask for confirmation of the proposed model’s diagram. Have the complete arrangement reviewed by the transformer’s system designer.
Explore the FYN33 four-position family ↗Discussion / Before quotation
Questions to resolve.
- Which terminals or circuits should be connected in each position?
- What transition sequence is required between positions?
- What continuity requirement has the system designer specified?
- Which model drawing and electrical-duty data need approval?
This article explains terminology for selection discussions. It does not authorize source paralleling or provide an operating sequence.
Technical references
Product family information: ZEEYI official loadbreak switch overview.
General terminology and connection examples: Eaton catalog CA800005EN. Manufacturer-specific ratings and drawings in that reference do not specify ZEEYI products.