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  • Users: nhee
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  1. nhee

    MV Motor Starts

    Thanks for everyone's responses. I don't have specific motor data yet. What would be the visible signs of too-frequent starting and stopping within the starter? Autotransformer failure? Contactor damage? Conductor discoloration/damage?
  2. nhee

    MV Motor Starts

    What is the normal maximum starts per hour/day for a 1500 HP MV motor, started w/80% autotransformer starter? What is the impact on the contactor/autotransformer if motor is started too frequently? Can anyone provide a link to reference data on this?
  3. nhee

    Motor Torque

    Thanks for the comments. It is an 80% RV AT starter. I agree the situation is odd, and it appears we may not have a properly sized pump. Unfortunately, I don't have a current/speed curve, only torque/speed.
  4. nhee

    Motor Torque

    Assumptions are correct - induction motor and load torque rises. How is the actual current draw calculated? Thanks
  5. nhee

    Motor Torque

    In comparing a motor torque vs speed curve vs a driven load (pump) torque vs. speed curve, the motor torque drops below load torque at about 80% of rated RPM. My understanding of the real-world result would be that the pump would start, accelerate to 80% rpm, and then hold that speed, drawing...
  6. nhee

    Soft Starter on 125 HP blower

    Thanks for everyone's follow-up. Just to confirm - at 15 seconds and 400% I don't overload. I had played around with lower current settings and higher initial torque settings and was seeing overload faults. Prior to playing around too much more, I was looking to get some suggestions for...
  7. nhee

    MV vs. LV Motors

    Good suggestions - we had made the same suggestion re: rental units but it is not an option in this case.
  8. nhee

    MV vs. LV Motors

    Thanks for the comments. BJC - the 480 VAC packaged units come pre-assembled with the RV starters (wye-delta). The 4160 VAC units require separate starters. In my analysis for the 480 system, a switchboard would feed the packaged units. In the 4160 option (units supplied without starters)...
  9. nhee

    MV vs. LV Motors

    A new facility will include 5 - 600 hp motors, along with roughly 200 KVA of 480 VAC load. It would seem to be an application requiring MV distribution and motors, but a cost analysis is pointing toward LV (480 VAC) - - The motors are part of packaged compressor units which are standard with...
  10. nhee

    Soft Starter on 125 HP blower

    Thanks for the responses. It looks like I need to obtain the curves for both the motor and fan, set a starting motor torque higher than breakaway torque for the fan, and adjust my acceleration ramp time as needed. 15 seconds was simply the default on the starter - the process can handle a...
  11. nhee

    Soft Starter on 125 HP blower

    Can anyone offer suggestions for configuration of an ATS48 softstarter in a 125 hp centrifugal blower application? Specifically, beginning settings for startung torque, current limit and ramp time? With ramp time of 15 secs, my current limit needs to be as high as 400% to allow motor to get up...

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