MPCB Type 1 vs Type 2 Coordination Explained

What is Type 1 vs Type 2 coordination for an MPCB? IEC 60947-4-1 defines two acceptance levels for what happens to a motor-protection circuit-breaker (MPCB) and its downstream contactor when a short circuit hits the branch: Type 1 permits damage to either device as long as no one is endangered, while Type 2 permits only light, easily-separated contact welding with no other damage. The choice changes what a technician finds in the panel after a fault trips it clear. This article covers how the standard tests coordination, what actually fails at Type 1 versus Type 2, how to read the two ratings against each other, why manufacturers publish combination tables instead of letting you size components separately, and where the extra cost of Type 2 pays for itself.

What the Standard Actually Tests

IEC 60947-4-1 does not rate an MPCB alone for coordination. It rates a specific combination: one MPCB model, one contactor model, and (if used) one thermal overload relay model, tested together at a declared prospective short-circuit current. Swap the contactor for a different frame size and the Type rating no longer applies without a new test or a manufacturer statement extending it. That single fact trips up more panel designers than any wiring detail in the starter.

The test procedure is blunt: apply a bolted short circuit downstream of the combination at the declared current, let the MPCB's magnetic trip clear it, then inspect the contactor and overload relay. Passing Type 1 means the fault didn't reach anyone outside the enclosure. Passing Type 2 means the inspector can close the panel and walk away without replacing anything beyond, at most, lightly welded contacts that separate with normal force.

What Survives and What Fails at Each Level

At Type 1, the magnetic trip inside the MPCB is allowed to let enough energy through that the contactor's contacts pit, the coil overheats, or the overload relay's current transformer saturates beyond spec. None of that is a defect in the combination — it's the accepted outcome. The panel gets a new contactor, sometimes a new relay, and goes back into service. At Type 2, the same fault current has to clear fast enough, and the let-through energy has to stay low enough, that the contactor's contacts might tack together but separate the first time the coil is re-energized.

The practical difference shows up in downtime, not in whether the motor branch is safe. Both types are safe by definition; the standard would not certify an unsafe combination under either label. What changes is whether a fault means "swap the contactor" or "reset and go."

The Coordination Validity Condition

A Type 1 or Type 2 rating only holds if the actual prospective short-circuit current at the installation point does not exceed the value the combination was tested at. Exceed it and the declared Type no longer applies — the outcome reverts to whatever an untested combination does, which is unknown.

This is why the coordination table lists a current value next to each Type, not just a pass/fail column. A combination can be Type 2 up to one current and Type 1 above it — some manufacturers publish exactly that split so the panel builder can pick based on the actual fault level at the switchboard, not the highest current the parts could theoretically see.

Type 1 vs Type 2 Coordination Compared

Why You Cannot Size Each Component Separately

An MPCB rated for 100 kA breaking capacity paired with an undersized contactor is not automatically Type 2. Coordination is a system property, verified by test, not a sum of individual ratings. The magnetic trip's let-through current and clearing time interact with the contactor's contact gap and spring force in ways that a datasheet for either part alone won't reveal.

What we see in the field: designers occasionally spec a Type 2-rated MPCB from one series with a contactor from a different series because both happen to be in stock, then assume the pairing inherits Type 2 performance. It doesn't. Manufacturers publish coordination tables (MPCB model + contactor model + optional overload relay) precisely because the pairing has to be tested, and only the listed pairs carry the declared Type.

Choosing Type 2 vs Accepting Type 1

Type 2 costs more, usually because it needs a larger contactor frame relative to the motor's full-load current, a current-limiting MPCB, or both. That extra cost buys shorter downtime after a fault — no small thing on a conveyor line or a compressor feeding a process that can't tolerate an unplanned stop measured in hours. For a spare pump on a non-critical branch, Type 1 is a reasonable choice; the branch tolerates a component swap without production impact.

This depends on the panel's role more than on the motor itself. A 15 kW motor on a critical mixer justifies Type 2. The same motor on a redundant standby unit often doesn't. Some panel builders default to Type 2 across the board to simplify their bill of materials, which is defensible on a large MCC but adds cost on a small OEM skid where it isn't needed.

Common Coordination Mistakes

Ignoring the declared current split

A combination listed as "Type 2 up to 50 kA, Type 1 above" reverts to Type 1 performance the moment the installation's available fault current exceeds 50 kA. Checking only the Type label without checking the current column is the most common error.

Mixing series across brands or families

Coordination tables are brand- and series-specific. An MPCB from one manufacturer paired with a contactor from another has no declared Type unless that specific cross-brand combination was tested and published, which is rare.

Assuming a higher MPCB breaking capacity fixes coordination

Icu tells you the MPCB survives the fault on its own terms. It says nothing about whether the downstream contactor survives too. That's a separate, tested property.

Conclusion

Type 1 and Type 2 coordination both satisfy IEC 60947-4-1's safety requirements — the standard would not certify an unsafe outcome under either label. The real decision is economic: how much does downtime on this specific branch cost, and does that justify the larger contactor frame or current-limiting MPCB that Type 2 usually needs. Check the manufacturer's coordination table for the exact MPCB-contactor pair and the current split between Type 1 and Type 2, size against the installation's actual prospective fault current, and don't substitute components outside the tested pairing. For the broader protection picture, see the MPCB engineering guide and how an MPCB's thermal and magnetic trips set up the fault the coordination test measures. Browse motor protection circuit breakers and contactors from tested combinations, and see building a starter from MPCB and contactor for the assembly steps, or the IEC 60947-4-1 standard overview for how coordination fits the rest of the starter's ratings.