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I'm working with a European company providing some control equipment for an off shore drilling unit. According to the specifications, the available power feed to our control system is 690V Delta "RI". I am having trouble with the "RI" definition ... basically I can't find a description for...

Talked to one of the more senior engineers. The intent is to block DC and low-frequency currents by connecting blocking devices (such as a cap or zener diode) between the cable sheilding and the PE ground. This would allow current flow in the sheild wire as well to prevent ground loops. I'm...

No, sheilds are not connected at the field end. It doesn't seem like a solid path to ground on the control panel end (all passing through a ceramic cap). Would this arrangement provide any noise suppression (I guess I'm not sold on the arrangement)? Main concern is the serial...

I recently ran into a client grounding scheme that I'm not too familiar with. I could use some insight from the group. For instrumentation (pressure transmitters, for example) and communication (serial coms), they connect the sheilds to a cabinet ground buss labled "IE" which I'm assuming is...

At first glance, the waveforms don't look that bad. You have to realize that I'm working this through e-mail (remote off-shore site) and the data doesn't have a real high resolution. Funny thing ... different rig with a slightly different application. Same ferro xfmer but feeding an on-line...

I believe busbar has described the original problem correctly. Most of the RMS-AC readings didn’t show any problems. However, the on site personnel was reporting a frequency jump in the 150+ range when load was increasing and the UPS unit switched to battery power. I do believe it was a...

Thanks jbartos - I'm really not looking for product info on ferroresonant voltage regulator transformers, but the problems involved in having two in series (feeding one from the other). It's my understanding that this type of xfmer produces a non-liner current waveform. When load increases...

Looking for some technical insight or a pointer to better understand a problem recently. A customer has a UPS (on off-line ferroresonate type) providing backup power for a control system. Because of power quality issues at another customer site, they have installed a power conditioning...

Looking for a formula to calculate motor heat load dissipation. I have a 100hp TEFC motor (460V 3ph) on our shop floor running continuously under normal load. In sizing a ventalaion system for this area, I'm trying to account for the heat generated by the motor.

Follow up. Problem with our test procedure rather than our math. Compairing data from a full battery discharge with objectives based on normal load. Found a good info source in the Exide website. An equation listed for lead acid type batteries: Charge Amp = ((Battery Amp x Battery Hrs x...

No, I haven't. Took the info out of the user's manual and didn't confirm with a meter. The configuration of the batteries is 2 - 10 battery strings. That would divide the charging current by half, but the output would also be half from each string. I'll take a messurement next time to...

Which is what I would have expected. The actual re-charge took over 15 hours. Somehow I'm off by a factor of roughly two.

I'm trying to calculate the charging time required for a UPS battery bank. I have a 260 Amp/hr battery bank (120VDC - sealed lead acid type) connected to a 6 ohm, 2.5KW resistor bank for 2 hours. This test is used to simulate the maximum foreseeable load and to chart voltage and current of...