BK32
Electrical
- Mar 25, 2014
- 20
I am currently reviewing a design of a new Motor Control Centre, fitted with a number of motor starters, of which a number are fitted with Siemens soft starters.
In the original requirements specification there was a requirement that all motor starter assemblies were type 2 coordinated assemblies.
Now that we have received the design drawings and specifications from the contractor, they have provided some type 1 coordination tables for the motor starters fitted with the Siemens softstarter. The tables provided show the specifications for type 1 coordination for a 400V system. The problem is that we are operating from a 440V, 60Hz system. Also, the contractor has deviated from the tested starter arrangements by using different circuit breakers.
Consequently, the contractor has provided a table of "estimated" short circuit values for which they believe the circuit breaker/softstarter combination will achieve type 1 coordination.
I have 2 questions:
1) Can you estimate, or determine by analysis whether a starter combination is going to achieve type 1/type 2 coordination? I have seen elsewhere where a fuse could be replaced with an equivalent as long as the cut off current and let through energy at the prospective short circuit current were less than or equal to the original fuse. Is this also the case with circuit breakers?
2) If there are no coordination tables for 440V, but you have coordination tables for the starter combination at a different system voltage (i.e. 400V) can you estimate the short circuit level up to which type 1/2 coordination could be achieved (i.e. by analysis)?
Thanks in advance for any assistance that might be provided here.
In the original requirements specification there was a requirement that all motor starter assemblies were type 2 coordinated assemblies.
Now that we have received the design drawings and specifications from the contractor, they have provided some type 1 coordination tables for the motor starters fitted with the Siemens softstarter. The tables provided show the specifications for type 1 coordination for a 400V system. The problem is that we are operating from a 440V, 60Hz system. Also, the contractor has deviated from the tested starter arrangements by using different circuit breakers.
Consequently, the contractor has provided a table of "estimated" short circuit values for which they believe the circuit breaker/softstarter combination will achieve type 1 coordination.
I have 2 questions:
1) Can you estimate, or determine by analysis whether a starter combination is going to achieve type 1/type 2 coordination? I have seen elsewhere where a fuse could be replaced with an equivalent as long as the cut off current and let through energy at the prospective short circuit current were less than or equal to the original fuse. Is this also the case with circuit breakers?
2) If there are no coordination tables for 440V, but you have coordination tables for the starter combination at a different system voltage (i.e. 400V) can you estimate the short circuit level up to which type 1/2 coordination could be achieved (i.e. by analysis)?
Thanks in advance for any assistance that might be provided here.