I am installing a VFD on a calendar Mill. Osha requires braking during a power failure. I was going to use a dynamic brake with a capacitor bank. The vendor I am dealing with insists that I have to install a mechanical brake. Does anyone know which standard states you need a mechanical brake ...
We need to perform a ground study for a Hexane process. Does anyone know what standard address how process pipes and tanks are suppose to be grounded ?
I have an application where we need to upgrade a drive on a two speed 5ooHP Synchronous motor. Can anyone tell me can I put an ac vectrol drive on this motor and if so what are the advntages and disadvantages ?
I have been told that if a have a Silcon carbide arrestor on the primary of a transformer and a MOV lightening arrestor on the secondary of the transformer. The Silicon carbide arrestors will cause the MOV arrestors to fail. Can someone confirm this?
NFPA 70E does not exclude single phase from its calculation methods. In Annex D.8 says if you use this method for single phase it will give conservative results. At this time since there is no better method of calculating Incident Energy.So this is the method you have to use
on DC where there is...
Sorry, I disagree ac will jump a large gap than dc, but dc will maintain the arc longer. The zero crossing has no effect on the arc.
The NFPA 90E calculations for arcing time are based on the overcurrent protective devices. This is what determines the arcing time.
The NFPA 70E Handbook specifically says in the definitions
that voltage means AC and DC. Which means the standard applies to AC and DC.
The calculations are all based upon RMS values. This means the calculations do not care if it is AC or DC. What this will do is give you conservative values...
Can anyone direct me to resources on Arc-Flash for DC. We have someone who uses 250VDC for overhead cranes. They would like some more infomation on how to comply with OSHA. They believe that NFPA-70E is gear towards AC and batteries. They are generating their own DC.
These do not work since when the pump has 21 foot of head the pump starts pumping at 100 rpm. But at 7.5 foot of head the pump will not start pumping until 433rpm. The PID works fine with 21 feet of head, but at 7.5 feet of head it oscillates due to the bottom end having do response. I believe...
We need to use a vfd and pump to control flow for a pump down application, where the pump is at the bottom of the tank. The problem we are having is that when the static head in the tank changes the pump charcteristics change. This causes the PID to oscillate. Can anyone give us some pointers or...
We use etap but it is missing some of the damage curves. I know one of the IEEE standards has generic damage curves in it but I do not remember which one.
