Type 2 Coordination is a well-specification process developed many years back in Australia and New Zealand, hence used widely nowadays all over the world. As described in AS/NZS60947.4.1 Type 2 Coordination is the coordination of motor starter components – Contactor and Overload, and Short Circuit Protection Device (SCPD) during a short circuit fault condition. The SCPD predominantly used is a circuit breaker, however, fused switches are still utilised in some applications. The devices must conform to AS/NZS60947.4.1 referring to the operational kW rating of the load, and testing on short circuit for a particular kA level (say 50kA).

Type 2 coordination is not a thing but just an immediate start without any work done on the motor on the starter under a short circuit condition. It is applicable for moving as well as fixed contacts.

For example, a motor attains a short circuit; it commands the contactor to open circuit. During this, all the starter equipment such as contactor, relays, MCCB or MPCB (not fuses), Cable, bolts should not come through any damage.

Initially the motor staring current goes up to 5-6 times the rated current. Then it starts reducing & returns below its Full load current (FLC) depending upon the load conditions. The total time taken by this activity is approx. 6-8sec.

Now, If the motor takes more time than this. Then there is an abnormality & hence needs to be removed by tripping. Here, we need overload protection. How??

If the prevailing more than FLC is grabbing more than 5-6 seconds, than it is noticed by an Overload relay. This gives instruction to Circuit Breaker & then it trips the circuit. But when there is a short circuit motor draws 10-12 times current. That huge current goes on for at least 3-4 seconds, then also it is dangerous & can easily damage the windings of a motor. There, the thought of an overload relay is not effective. What would we do next?

The solution is Power fuse characteristics

The point at which the characteristics of overload relay & power fuse intersect is referred to as crossover point. This point is kept at 8 sec. (approx.) so that after this time, the fuse does not melt & the overload relay trips the breaker.

If the motor draws heavy current in a short circuit condition, then the fuse melts down for protecting the motor windings. Now, how to protect contact welding?

This reduces the contactor breaking capacity up to 5 times the value of Motor FLC. With this, weld-on contacts of a contactor reach and weld before its sensing by the relays. Thereby, an undetected dangerous situation may crop up even while receiving the command in relays to switch off the current flow.

Therefore, we maintain contactor breaking capacity higher, approximately 12 times the FLC. However, the fuse unit gets melted & trips the power supply which acts as an advantage in such situations.

Principles and Guidelines for Type 2 Coordination in Motor Starter Protection:

• No risk to personnel or plant
• SCP still operationally valid, without damage
• The motor contactor to be undamaged, if light welding did occur this is accepted, provided it may be separated by a simple tool, and the contacts are not deformed
• The overload shall be in operational condition, and still within calibration limits

This allows for a starter to return to service for further use, without replacement of any components that may be required under Type 1 Coordination.

Manufacturers recommend regular scheduled maintenance, for a detailed inspection to ensure the starter components will be able to function correctly in the event of a future short circuit fault.

Standard Type 2 Coordination tables usually outline suggested tested device combinations applied in motor starter cells or assemblies for normal AC3 kW ratings, installation at nominated kA fault levels, and supply voltages.

Benefits of Type 2 Coordination for Modern Industries

With such innovations, Type 2 Coordination remains beneficial to industries operating on motor-driven systems. The following are the benefits:

• Less Downtime: Improved fault handling and durability of components ensure that Type 2 Coordinated systems keep the motors running even after short-circuit faults, thereby minimizing the need for expensive repairs or replacements.
• Improved Safety: The latest standards ensure that safety is not compromised, even under high fault conditions. This protects both personnel and equipment, ensuring that the system remains operational with minimal risk.
• Cost-Effectiveness: This is because Type 2 Coordination enables faster recovery from a fault and minimizes the extent of component replacement, hence reducing maintenance and replacement costs.
• Proactive Maintenance: The incorporation of smart monitoring technologies allows operators to identify faults early, thereby preventing catastrophic failures and extending the life of motor control systems.

Type 2 Requirements

DOL starters require a circuit breaker, a contactor and/or thermal overload combination that has been certified to type 2 by the manufacturer. The additional cost is small. For Soft Starters, semiconductor fuses may also be required, and this can add to the cost and require additional cabinet space.

Type 2 Coordination remains an essential part of motor control safety, evolving to meet the challenges of modern electrical systems. The latest advancements—ranging from enhanced fault-level handling to smart monitoring technologies—ensure that motor starters are better equipped to handle short-circuit faults while promoting operational efficiency, safety, and sustainability. As the industry continues to innovate, Type 2 Coordination will undoubtedly play a key role in ensuring reliable, safe, and cost-effective motor control systems for years to come.