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  • Users: GordS
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  1. GordS

    Two starts from cold... allowed for routine planned operations?

    We don't place any such restrictions on our consecutive starts. My reasoning is typical stall times for our motors are in the range of 8-12 sec but typical start times are about 2 sec.
  2. GordS

    Conveyor Tracking

    Is your feed dropping on the center of the belt? In our plant, the feed hits batterboards that an operator adjusts to direct the feed onto the center of the belt. If the belt is not tracking correctly, he will move the batterboard which changes where feed drops and moves the belt.
  3. GordS

    HV contact type voltage tester

    I am looking for any feedback from people using a contact type of voltage tester at voltages > 1 kv. The intent is for confirmation of isolation. What do you use? Have you tried any other contact type tester? What voltage range is this tester used upon? Any feedback on ease of use, reliability...
  4. GordS

    Bar-Type CT Failures

    What is the neutral resistance let thru amps with respect to the LV system charging current ( i.e capacitive amps due to cables, surge caps, etc). If the former is less than the latter, than transient overvoltages are possible during an arcing groundfault which would impact all equipment on a...
  5. GordS

    VFD Overvoltage Problem

    Recently we had an incident on a bus feeding multiple PWM style VFDs, motor loads and small transformers. The bus is high resistance grounded, limited to 2 A. Over a span of about 3 hrs, 3 drives tripped and a transformer shorted to ground on the primary. Several of the drives would not restart...
  6. GordS

    CSA

    Ckeck out 12-904(2)
  7. GordS

    arc flash boundary for synthetic fabric

    Could you say that the line is defined by the limited approach boundary within which an unqualified person may not approach as per the 70E standard, item 2-1.3.5.2 and 2-2.4?
  8. GordS

    VFD Isolation Transformers

    Common mode problems increase with the newer drives due to electronic devices that switch a lot faster than the older style of drive (i=C dv/dt). In my opinion, if you are going to do an installation with a lot of electronic devices and drives, put in isolation transformers solely for common...
  9. GordS

    hazardous location motor thermostat leads

    CEC 22.2 77 is for motors with inherent thermal protection which must be labelled "Thermally protected". This labelling indicates you need to connect the thermal device into a control circuit. Where exactly in CEC 22.2 145 is it required that explosion proof motors NEED a thermostat ( or...
  10. GordS

    hazardous location motor thermostat leads

    Where in the CEC does it say TEXP motors must have temperature limiting devices? Repair shops, I believe, need to install these devices on motors they repair. In Alberta, there used to be a standata that required us to connect these devices if they were present; this requirement no longer...
  11. GordS

    Ground Currents in Parallel Feeder Equipment Grounds

    Currents in equipment ground conductors are normal. I think they result from the ground conductor not being equidistant to all of the phase conductors. This means the magnetic flux due to each phase that links the ground loop does not cancel out. Faradays law says a voltage is induced in any...
  12. GordS

    investigating a lug failure and subsequent motor trip?

    Hi Pete I don't think I would assume the pit by "A phase is copper splatter because it is nicely centered in some black soot. I associate the soot with current. The presence of black soot indicates enough current that resulted in equipment damage. In a recent failure I was involved with at 5 kv...
  13. GordS

    Remedy for switching transients- 4160V motors

    If you add surge protection AND you are on a high resistance grounded system, be aware of the amount of charging current vs the resistor let thru current. Surge caps will be a source of charging current. If the sum of charging current on the system exceeds the neutral resistor let-thru, you can...
  14. GordS

    How full Cable Tray is full

    I would say no, you need to include ALL power and lighting conductors. CEC 12-2210(4) refers you to 4-004(7) when deciding which conductors are to be included in your calculation.
  15. GordS

    HV motor stall protection at start-up

    Is it possible that the speed sensor was installed for Process reasons? Is there a need for the load to be at 60 rpm within 2 sec? I interpret your post as the motor being capable of 7/10 sec safe stall times but your protection is set at 13 sec. If so, then I would say the motor is not...
  16. GordS

    VFD for decanter centrifuges

    You do need to be concerned about the motor being compatable with the VFD. The options involve either specifying a different motor, rewinding with spike resistant wiring ( likely more cost effective to buy a new motor at this low HP), or install output filtering. Consider also the impact on...
  17. GordS

    Inverter Duty Motors

    NEMA MG-1 Part 31 deals with Definite Purpose Inverter Duty motors. When we specify motors, we use ask that the motor be built according to the standards of NEMA MG-1 Part 31 in an effort to quantify what we mean by inverter duty.
  18. GordS

    Repeat Drive Failures on Overhead cranes

    Since it is the control board that is failing, is there a chance of inducing harmful voltages on the control wiring due to proximity to power conductors?
  19. GordS

    Pushbutton maintenance

    I have been having a problem with pushbutton operators sticking in a Cl 1, Div 1 inside location. Does anyone do maintenance on pushbuttons? What do you do? What material do you use to clean the operator shafts? I have asked the vendor for guidelines on this topic and have received no answer.
  20. GordS

    AC Motor Ramping Startup

    Sounds like a job for a soft starter. Basically, these units gradually increase the voltage applied to the motor. This gradually increases the torque generated by the motor so it gradually accelerates. These are off-the-shelf units made by many companies. Check the internet.

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