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The inherent problem in paralleling thyristors is that they are constant voltage drop devices, but finding two that are the exact same voltage drop is virtually impossible. So the one with the lower VD, no matter how small of a difference, will hog the current. Then you combine this with the...

I like to look at IEEE-519 as being the Tablet brought down from the mountain that says only one commandment: "Thou Shalt Not Infect Thy Neighbor's Facility with Your Harmonics!". So then you have to look at harmonics like it's a "population of a country", which is made up of individual cities...

Parallel inverters are frequently done now for large drive applications, but not in the field. The inverters must be designed for that from the outset, typically using fiber optics for the firing controls to minimize latency in synchronizing the outputs. Most stand-alone single inverter drives...

That has not been true for decades... Almost all modern VFDs are around 97% efficient at full load, dropping to around 93% (depending on mfr) at 40% I'll just point out that energy savings on variable flow applications with CENTRIFUGAL machines (pumps and fans) using VFDs is not a theory or a...

A better way to look at it is that IF you were going to use PID control on a throttling valve as a way of attaining flow control, the VFD will save energy COMPARED TO the use of the throttling valve. But the use of PID control is not in and of itself done for the purpose of saving energy...

Some of the tulip system maintenance manuals specifically warn you NOT to put grease on them, they claim to be "permanently lubricated" and putting anything on them strips that lubricant off. But that said, if you do have to use it, in a previous life our field service team used stuff called...

A PID loop needs to "follow" something called a "Process Variable" (or "PV"), maintain a "Setpoint" (or "SP"), and actuate a "Control Variable" ("CV"), while avoiding deviations, a.k.a. "errors", as much as possible. So what's you goal here? Flow rate that varies with viscosity? Pressure in a...

ACBs are designed to be serviced and rebuilt, MCCBs are not. As an isolator it likely wouldn’t be damaged unless there was a fault, but if that happened, the MCCB would have to be discarded, whereas the ACB could be repaired. I’m not sure how important that would be to someone, I’m just pointing...

There are circumstances under which voltage escalation can take place in an arcing fault situation on AC lines due in part to constant reignition of the arc acting like a capacitor. I’ve only read about it in regard to ungrounded systems, but maybe it can happen with an impedance grounding...

That would be MCB, not MCCB. MCCB = Molded Case Circuit Breaker. Different product, different standards. " We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden

The "D, G, J, L" etc. followed by your statement about using type D for motors sounds like trip curve designations for IEC MCB (Miniature Circuit Breaker) devices, so would not apply to anything in North America where we don't have those. But I have only heard of B, C, D, K and Z trip curves, no...

It's been years since I have programmed an ABB drive, but I believe you have that correct. In the "inverted" operating state (-1), the NO contact would be held closed when "normal" and drop out (open) when there is the fault that you programed it to. As I recall though, when the drive is...

Most of the major brands of MCB suppliers, Siemens, Eaton, ABB, Schneider, Rockwell etc., have aux contact module options available. But they are not going to be IN the breaker, they will attach to the side and increase the width. Some have limitations as well, i.e. only one added accessory...

Rockwell (Allen Bradley) has an on-line MCC design tool called "Centerline Builder". But it can only configure STANDARD units, no modifications, nothing special, nothing that needs engineering. It's free, but you need to register...

You can’t, you have to be on the Round Table to have that feature. We use it in thwarting spammers and other “undesirables”. " We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden

And where. It’s only a very small number of countries that use 380V at 60Hz. That’s just for satisfying my curiosity though. Of the available choices, it would pick 400V. Most machinery is built to be able to do fine with +-10% on voltage. So if the machine is rated for 400V, and the feed is...

I’ve never seen it done. I would think that would come with some undesirable baggage. For one thing, you would need to add a bypass contact, otherwise the resistor is just going to burn out in short order by being in the circuit all the time. So now you have another part to fail. You already...

I see a lot of people who don’t seem to understand the concept of a high resistance fault not being cleared by circuit protective devices. I think there has been some inadequate education on that front. I just looked into a n incident where the load terminal of a 400A breaker completely melted...

I never assume that the VFD built in fans will move heat OUT of the box. Their job is to move air across the heat sink fins. By the time that velocity gets reduced in that task, I don’t assume there is enough flow to get it past the filters. " We are all here on earth to help others; what on...

Zero Cross Variable Time Base SCR firing results in a change (lowering) of the average VOLTAGE that gets to the RESISITIVE load. But no matter what, the maximum CURRENT that can be drawn is dictated by the resistance value. So regardless of the burst pattern, the maximum current seen by the...