Electric motors are the backbone of manufacturing industries and operated correctly they can also provide decades of reliable service. Choosing the optimal motor starter coordination for each application keeps plants operational and controls costs.

Motors play a vital role in a wide variety of roles from pumping to material handling. This means that any failure or unplanned downtime can have wide repercussions on productivity and profitability.

Overloads are the most common cause of failure. Under these conditions the motor draws excess current which causes overheating, leading to undue wear and resulting in failure of the motor. More worrying are the short circuits that occur in motor applications, as they pose the greatest dangers for the equipment, the installation, and for personnel.
Short circuits can cause a sudden and massive surge of current within milliseconds that can melt and destroy contacts, produce electrical arcs and even explosions. They can also cause wider physical damage and fires.

IEC standards help motor starter coordination

The IEC recognises that motor control for short circuits needs addressing to ensure safety of personnel and equipment. To meet this need, the IEC has developed specific standards to ensure the safety of motor starter combinations. Achieving this is through coordination between the control and protective devices.
A ‘coordinated starter’ is a tested combination of short circuit protection (fuses or circuit breakers) and overload protection devices. Moreover, testing of the motor starter combination happens under extreme conditions, with faults cleared quickly and without damage to the installation or risk to the operator. This makes it the optimal tested combination of devices to ensure safety.

Coordination types

There are two types of coordination included in the IEC 60947-4-1 standard: Type I and Type II. There is also an additional level of coordination specified by IEC 60947-6-2, that Schneider Electric refers to as ‘Total Coordination’.

– Type I Coordination. This coordination level provides a basic solution that balances uptime and cost effectiveness. It is a viable choice when machine uptime is not a priority, as this level does not provide continuity of service. Before restarting the motor, it is good practice to replace the starter.

– Type II Coordination. This is a high-performance solution, providing reduced machine shutdown time and reduced cost of equipment replacement. The motor starter must be ready for reuse after a fault, with only a simple inspection needed, and any welded contacts must be easy to separate.

– Total Coordination. This is the highest possible performance and ideal for mission-critical operations and processes. There is no damage to the equipment and following the fault the starter must be immediately reusable. It needs no resetting or inspection. Furthermore, the installation can return immediately to operation. A different standard applies to this level of coordination as defined for combination devices with multiple functions.

Different coordination levels have a range of benefits, from protecting people and equipment, to permitting a greater continuity of service. Moreover, they reduce both downtime and maintenance costs by avoiding the time and cost of replacing equipment.

Selecting a motor starter

Firstly, users should first determine the level of motor starter coordination that suits each application and business requirement. Secondly, choose a manufacturer that tests and complies with coordination standards for their motor starter.

Schneider Electric offers a wide range of motor starters and coordination tables. They include DOL and Star-Delta starters, Tesys MPCBs with advanced protection, motor management relays, configurations for Total Coordination, drives, and soft starters.

Finally, for different equipment configurations, try the EcoStruxure Motor Control Starter Configurator to select the optimal combinations of components.