brianafischer

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About brianafischer

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  1. DC Motor Control and Overload Protection

    Thanks for the reply. You are talking about the "Output Parameters": "setup rise time" and "setup hold time" here, correct? Don't you mean the PSU can hold overload current (67.5A) for 20 msec? Isn't this extra power coming from an output capacitor that will drain after 20msec? The product page for the fan is here and the data sheet is here. This fan is used in a system that will use ON/OFF control (with a minimum safe ON time for me to determine) that will be used to control the temperature. I know there are easier ways of doing this, but the purpose of this configuration is to simulate automotive conditions. I would like to provide adequate power to the fans so the start-up of the fans does not derate the life (which could occur if the voltage dropped too low during inrush due to current limiting). My current plans are to use two of the PSP-600-12 series in parallel which could support up to 135 amps. Is this overkill?
  2. DC Motor Control and Overload Protection

    I am specifying a power supply to provide power to two 12VDC fan motors. These may be switched on at the same time. The motor has the following inrush current curve: The voltage needs to be maintained at 12V over the following motor start-up current 80A @ 20msec, 55A @ 40msec, 35A @ 140msec, 25A @ 220msec I see that the PSP-600-12 has a 12VDC, 0-50A output. The Overload Protection is 105% - 135% (67.5A) constant current limiting. Any advice/opinions?
  3. In the process of designing a closed-loop motor control system, I noticed some conflicting information regarding encoder connections. The system utilizes an Emerson Control Techniques UniDrive with a Danaher encoder. After thoroughly reading the documentation, each manufacturer seems to recommend conflicting advice! Please see the attached excerpts from the user manuals. Emerson Connect the cable shields to the 0V common and clamp the encoder cable at BOTH ends. I also don't appreciate the following verbage: It seems that if my case of doubt so happened that the encoder case WAS grounded (through the motor and surrounding frame), and I connected the encoder case to the drive ground, I would be creating a nice ground loop between the motor ground and the encoder! Danaher The standard practice I have seen: Ground the encoder case ONCE using either the mounting bracket or the case lead (if no continuity to system ground on the case lead) Use twisted-shielded pairs Connect the shields to GND only at the instrument end I find the Emerson manual quite interesting. So, the question of the day is: when have you used the Emerson technique and how/when is it applicable to ignore the encoder/sensor manufacturers suggestions and follow the drive manufacturers suggestions? Thanks, Brian danaher_encoder_suggestions.pdf unidrive_encoder_suggestions.pdf
  4. NEC 2008 Discussion

    I just got an e-mail from amazon announcing the NEC 2008, located here. Anyone have any comments or a discussion regarding the new revision?
  5. DC Motor Control and Overload Protection

    I would like to avoid this at all costs, but a simple fuse may not stop a DC motor from running away!
  6. I am currently investigating 12 VDC motor control. The control panel has a 3-phase 480VAC drop and the goal is for ON/OFF control of a 12 VDC 20 amp max continuous motor. The duty cycle is a minimum of 5 seconds ON/OFF. I have seen many DC motor control designs that incorporate a simple high-current relay such as this with no overload protection. My concern is the lack of an overload for the motor due to the frequent switching. Almost all AC motor designs incorporate motor starters with overloads. How can this achieved with DC motors, and what are your suggestions for motors operating at 12VDC? Thanks!
  7. Importance Education in Automation?

    My employer offered 100% reimbursement. I am fairly young, married, and no kids yet. From my point of view, who would turn down a free education? I will be done this December actually. The problem that I am having is attempting to implement the "tools" I have learned through graduate school. I can see some applications in the testing field, but nothing that can be directly applied to the automation field. One of the valuable skills I am learning is problem solving extremly complex systems (through matrix manipulation). Anyways, thanks for all of the feedback. It is nice to get a discussion going on this forum every so often. -Brian
  8. As I sit here studying for an exam late on another Sunday night, I find myself asking the same question over and over again... Is a Masters in Electrical and Computer Engineering worth the time and effort? What does a masters degree get you in the automation field? It seems that the automation field is unlike other disciplines, where technicians can move up to a design position. My current job has a heavy concentration in testing applications, which can require knowledge of advanced concepts. However, in general the automation field only requires a "basic" understanding of concepts. Anyways, what are your thoughts? What education background do you have? Thanks!
  9. This purpose of this topic is to gather strategies for cable and connector selection in industrial control design. Cable Selection When do you use twisted shielded?mV signals that have a differential input When is a braided shield acceptable? Is it cheaper? When is a combination of foil and braided shield necessary?Braided is good for high voltage and VFD signals, but usually use Bedfoil AND braided How to check prices/what web sites do you use? (Belden vs Carol vs ...)I use newark.com and alliedelec.com Who is the most "cost effective" cable you have found?General Cable or "Carol" is sold at Grainger (The Belden to Carol Cross Reference here is useful) It seems that most use Computer Cable instead of the Industrial Automation & Control (Cost Savings)? When have you used industrial automation and control cable? What does one make of the insulation types? (Polyolefin, Polyethylene, Polypropylene, Plenum) What is the typical insulation type, and when to move to others?Looking at the 9502 Computer Cable, it is suggest "For Plenum" to add an 8 in front (89502). When is plenum necessary? Do you use any mixed-gauge wire?This can be useful for solenoid manifolds (where the common is returning the current of ALL solenoid coils) Where do the UL AWM styles come from? Is there some sort of lookup table?I found some info here Multiconductor Cable When is it OK to mix low-power (< 25W) signals (120VAC/24VDC) in a multi-conductor cable? Junction Boxes/Shielding/Connectors If junction boxes are involved. How do you route the wiring? Do you maintain the shields through the terminals, or do you ground shields at the junction box? At the main panel Do you combine shields through a single pin on the connector, or do you terminate on the connector? What type of connectors do you use with multiple cables? (Example: Multiple Belden 9501 in conduit, harting connector, circular connectors, and so on...) What type of sheating do you use around multiple cables?I like to use Braided Polyester Mesh Sleeving [*]What type of connectors do you use for high power VFD applications (480VAC > 100A)? Tips and Techniques I like to look at the AB knowledgebase for recommended cable types (i.e. RTD = Belden 9501 or 9533). I will look for a matching AB PLC module, and then use the cable type specified by the AB document. The Belden Cabling 101 document located here is a decent reference. Please add your advice to this thread, any info is appreciated! Thanks...
  10. Supplies for the Common Controls Engineer?

    FYI, I reccomend using a hub or "managed switch" but not a switch. With EtherNet/IP you cannot monitor traffic with a normal switch.
  11. Supplies for the Common Controls Engineer?

    A few extra things that have come to mind: Tape Measure Leatherman or other Multi-Tool (I use the knife/scissors a lot!) USB Floppy Blank Cd/DVD Media (great for giving customer files and PC backups)
  12. I am attempting to compile a list of supplies that a common controls engineer would use. I think this site would be a great source of feedback for additions/advice... My list so far: Laptop computer w/serial port Programming cables (how do you sort them? maybe I'll add a list of them all later..) Roll-around cart for on-site support/travel USB KVM for connecting desktop/laptop (Trendnet TK-207K KVM Switches) Please add your advice/comments. Thanks
  13. Looking CX-Programmer 3.0 Installer

    And that is my dilema as it is the only disk we have!
  14. Looking CX-Programmer 3.0 Installer

    Hello, I am compiling automation software for my company, and located the license and registration code for our copy of CX programmer v3.0. Although I have a disk for the 3.2 upgrade, I do not have the disk for v3.0. Omron suggested that I look online and contact anyone to obtain a version of the 3.0 installer. Can anyone help? Thanks!
  15. Converting Time on MicroLogix and PanelView

    I modified the program to display weeks, days, hh:mm:ss. The machine displays when the current cycle will complete and when all cycles are estimated to complete. Below is the logic I used (untested). WDHMS_LONGPERIODTIMER_ML1200.RSS -Brian