Search results

Michael is right-on. Much of the oil-patch industry uses/used 830V... and yes, that value is sqrt(3) x 480V (ca). Some time ago I presented a study that demonstrated considerable savings if a refinery's LV distribution system was 830V instead of 480V. The savings, of course, was related...

How about pulleys and thread? Regards, Phil Corso, PE Boca Raton, FL [[email protected]] ([email protected]) {[email protected]}

Responding to David Adams and Robert Trask replies: I am very interested in what you identified as ... "Some on the money, others... absolutely wrong." This is, after all, a List that members use to elicit help. Others impart knowledge. I'm sure that those with wrong answers would...

Responding to the original query, yes, a 380V motor can be operated on 440V, but it shouldn't be. Although frequency, i.e., 50 or 60 Hz, has an impact on the discussion that follows, it is omitted for clarity. Load changes and cooling fan variations are also ignored. Now the reason why it...

Responding to Anonymous' original query: For the first part... Yes, the resistors used for the closed-transition starter are initially connected in parallel with the windings. For the second part, sizing, a greater issue must be addressed! The very fact that you are considering a...

Each designation refers to a 3-phase, 4-wire source of power. They are used to supply power to both 3-phase and single-phase loads. In other words in addtion to the 3-phase wires carrying current, the neutral wire can too. For example, in the USA, the first is properly designated as...

Responding to E99Beekz's query: Search web for Hall-Effect Sensor manufacturers such as Cherry, Optek, Panasonic. Others may already have hall-effect sensor assemblies such as the one you seek. Regards, Phil Corso, PE Boca Raton, FL [[email protected]] ([email protected])...

Responding to Qball's query: For an induction (asynchronous) motor the maximum efficiency occurs when load losses equal no-load losses. The above is based on the standard motor model, from which output torque, hence output power, and efficiency, vs speed can be calculated...

There is no one sentence answer. Some of the principle requirements concerning "duty" are related to nominal or running torque, startup or acceleration torque, starts or reversals per hour, moments of inertia, driven-machine applications, available cooling methods, etc. I suggest as a...

To Loveland: If you have the transformer capacity at 480V, then that is obviously the way to go. However, if a larger transformer is required, then 4160V is better suited for the 600 hp motors. If you are interested in alternatives, please provide details of existing facilities...

Addressing paulshades reply, Although the original query concerned DC, your reply covering AC contains an error that too many engineers make: For the Star-Delta case the nominal current for each of the 6-conductors between the starter and the motor equals (0.577) x (1.0/0.8), or 0.72 times...

Anurup, Are you talking about a slab that is first produced by conventional crystal growth methodology, at which time impurities are added, and then, in effect, performing some sort of machining "operation" to produce the "shape" you describe? Regards, Phil Corso, PE Boca Raton, FL...

The correct cable size should be determined based on expected, or allowable, voltage drop for a given load. Assuming the load power-factor is known, then, the correct formula for voltage-drop of a specific wire-size is: Delta U = sqrt(3) x I x L x [R cos(phi) + X sin(phi)], where: U =...

John Boland, Excellent reply. You certainly provided a very good analysis & solution... "out of the box" in today's problem-solving jargon"! I lost interest when the "can't do anything" comeback was made. I interpreted it to mean... "someone screwed up, and now it has to be fixed, but...

Try: 1) The Don Lancaster "Cookbook" series for electronics. 2) Go to a tech school / university library or bookstore, for the most recent "Guidebook of Electronic Circuit Schematics." 3) Try the REA (Research & Education Association) "Problem Solver Series" covering electronics...

Steve, You are correct regarding application criteria. The very first two applications to use the then new NASA patent (eventually to become VFD or VSD) were a total failure. One caused a refinery fire. The other revealed that reducing the original motor size by 50% would have saved an...

Dick, Do you remember how ecstatic the refinery control potentates were when they discovered (late 60's) that NASA' simple patent for controlling motor speed could, potentially, save lots of money... a fact that the chem boys knew from day one! It was also the main reason EXXON bought...

John Boland, An excellent analogy. Anthony Hillard, Have you looked into a second level measurement diametrically opposite the original location. Even a third, etc, if "roll" dirction is unpredictable! Thenm average their outputs. In theory the pump is compensating for the volumeric loss...

Sekar, Don't be so critical. The "cold" resistance is a good start for a calculation. And, I believe most heater users know that the rated kw is given for "hot" resistance! Regards, Phil Corso, PE Boca Raton, FL [[email protected]] ([email protected]) {[email protected]}

Could be inadvertent grounding of the pressure sensor. This will cause the 7805 (+5V) regulator to fail on short-circuit or thermal shutdown. Is the sensor circuit fused? Regards, Phil Corso, PE Boca Raton, FL [[email protected]] ([email protected]) {[email protected]}