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I use 80% service factor when I size equipment. Switchgear sized at 80% of projected load, then transformer rated for 80% of the switchgear. But then again, I see how much mechanical oversizes pump, fan motors and I have a general idea how much things will be loaded. Of course I do take into...

waross, NEC is a great sources for overcurrent protection, wire sizing etc, but as you may find it does not go into sizing based on service factors, loading etc.

Recently I have gotten myself into sizing medium and low voltage switchgear and I have several questions. Where can I find some good general sizing rules for switchgear, such as: - Bus sizing taking into consideration MCC loading and other sources. - Tie switch sizing in main-tie-main...

Thank you everyone! All clear now!

I'm a little confused about the name plate data on a transformer. I am trying to find the Nominal KVA and Full Load KVA for a tranformer. Here is the name plate data: Westinghouse 4160 - 480Y/277 60 Hz 3 phase Type RSL Unit Substation Transformer Class OA Full Load KVA = 2000/2240 Deg C...

Well, lets see. I will try to provide more details. This is just a general question. I need a list of requirements for a VFD application. I'm not sure if this is the right question to ask. I know if you have an old motor, if you want to put a VFD on it, you need to meet specific insulation...

We have several large motors with possible VFD applications, but I have some concerns. The motors are 1960's vintage. There is a good possibility they have been revarnished sometime in the past. My question is, where can I find a good list of requirements which have to be met for successful...

Thanks guys! I will read through it and see if any questions come up!

We have a 6k, 6.9kV Rotor Would Indiction motor that was probably built back in 40's. It is connected to a Liquid Rheostat control that is probably just as old as the motor. There isn't too much documentation on the liquid rheostat. Does anyone know where I can find some good information about...

Thanks guys. I found a calculator on ABB's website if I can get a hold of pump data.

The pumps run at 100% loaded 24/7. Water is recirculated, and amount used is either diverted back into system or used in process.

I'm trying to find what the advantage would be of using a VFD vs a soft start on a motor Motor: 460V 350HP What would we save if on average I ran three pumps at 75% using VFD vs running them at 100%. I understand that VFD has some losses associated with it, and the losses increase as you...

Thanks guys, it makes perfect sense now!

This is a simple question. I am trying to calculate electricity usage of a large motor: 3 Phase 20,000 HP Voltage 13800 Idling: 280 Amps Motor PF Rated: 0.8 Actual PF: 0.2 KW = (13800 * 280 * 1.73 * 0.2)/1000 = 1336.9KW My question is, power factor plays a big role when it comes to power...