Amendment 5_Questions and Answers.pdf

837 Converter Questions

Question 1

To achieve the scope of this project we will need to shut down all power feeding the distribution center that the input and output power runs through for the converters. We will need exact breaker locations feeding this distribution so that lock out tag out can be installed.

Main Panel location

This is the picture of the main panel inside mechanical room room in first floor

The 2 top breakers from the main panel labeled 400Hz are the breakers for the converters

This Panel is located at Mezzanine 2nd floor with the converters

Inside the Panel there are 3 breakers “north bay breaker” is off I believe this breaker is also connected to the converter that needs to be replaced

This breaker also has lock out tag out capability but I would recommend contractors to have their own lock out tag out throughout the installation because no one should be able to access lock out tag out but the workers

This is the one line diagram on how everything is connected the contractor should be able to see where circuits are going

Question 2

How much notice does the base need to loto the power for the distribution? (not sure what is meant by “loto”?)

I would say all you need to do is communicate with 837 facility manager depending on the mission if there are aircrafts being serviced and they need that equipment all the contractors need to turn off is the breakers connected to the converter circuit but if they will turn off the main breaker for the whole building CE needs to be notified. LOTO means Lock out Tag out I believe. I would recommend contractors to use lock out tag out where only the workers can access for safety.

Question 3

It does not appear that the existing conductors will be able to be used. If new input/output conductors are installed do they need to be in separate conduits? The existing installation has input/output in same conduit but it is our understanding that running 60hz and 400hz in the same raceway can cause performance issues

I was trying to find this in NEC but this is how I see it. It is not good having in different frequency in one conduit. The reason for that is conductors with same frequency has mutual inductance to each other is cancelled out but if you have different frequency creates induction and will end up inducing voltages and current to each other which is not good for the circuit.

Question 4

The scope of this project is to replace the converter only, has the base tested the existing conductors, cable reel and receptacle to verify they are in working order?

They have not tested the conductors, cable reels and receptacle. But contractors will be testing them following installation of a frequency converter to make sure their converter works correctly. If the conductors, cable reels and receptacle are not working correctly the contractor shall report them to the government POC.

Question 5

The converter specification calls for the converter to be equipped with the E&F aircraft safety interlock. How is the E&F interlock signal transmitted up to the converter? Are the E&F control wires from the service points ran up to the converter directly or is the interlock monitored at the service point on the floor?

Our best guess to answer your question is because there is a switch (dead man) at the cable head, we think that would mean that the interlock is monitored at the service point on the floor