LIM Safety

[berkgokmen14]

From the safety guy. Focus on point 2:

1. The motion of the large aluminum wheel need to be considered to ensure no accidental contact with it or that it does not break free / apart and fly off to hit someone. Even with the relatively low planned rotation speeds (300 rpm max), we need to plan for unexpected operation where it might be going faster. Joe can provide some information on suggested ways to guard the wheel that will not impede the airflow or testing.
   2) The contractor used for the thermal protection will also be important as a safety cut-off of the system. The 12 V loop powering the contactor should have an Emergency Power Off (EPO) button wired into the circuit. Additionally, the EPO circuit should be a latching circuit, where it does not power the contactor automatically when the thermal switch cools off again. Here is a quick video on how to create a latching circuit (https://www.youtube.com/watch?v=ySVq9O6VSaE). Basically it should be one where you have to push a button to arm it and if the EPO is pressed or the thermal switch opens, closing either of them does not reset the circuit again. Instead you have to positively choose to repower the device by pressing the interlock “on” button again.
2. The contactor should interrupt all three phases of power, not just one. It appears you are powering the VFD from the 3-phase 208V power, so the contactor should interrupt all three phases to prevent a ground fault or other issue from allowing power to continue to run somewhere when the interlock is tripped.
3. All of these power connections need to be done with wire rated for the current and voltage, which you appear to be doing. All power connections need to be inside a secured electrical enclosure rated for the voltage contained, and all wires going through the enclosure secured appropriately with a rated securing method. The attached file is an incomplete draft of an electrical safety standard I was working on, but it covers the basics of enclosures. If connections need to be made for voltage/current measurements, they need to be within the enclosure, and no manual wires carrying the high voltage outside of the enclosure for metering with a multimeter. So this means you need to have sensors that send out a lower voltage signal outside of the enclosure.
4. There should be overcurrent protection (fuses or circuit breakers) for all power sources (3-phase to VFD and 12V interlock source).
5. The setup will need to be inspected by a licensed electrician from the Cornell shops (Brian Pakkala) for safety and adherence to the National Electrical Code (NEC). This may require a charge to pay for his time. Work with Noah on scheduling / paying for that.

Dan

Daniel Woodie

Safety Manager / Facilities Engineer

College of Engineering