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Recent content by che12345

  1. che12345

    Busbars on edge distance and derating

    I have following additional opinion for your consideration. 1. If 900 A is FLA x 1.25; that is you had taken "the code in many places and good practice to limit maximum continuous loading to 80% of the maximum ampacity". Attention: The size may base on 900 A. Do NOT derate further by 0.8 factor...
  2. che12345

    Busbars on edge distance and derating

    I have the following opinion for your consideration. 1. In most cases, busbars are of short length say < 30 m. As their resistance and reactance are very low, therefore the voltage drop is of NO significance. For your case 2.5 m (10'); ignore it. 2. For installations in the US, take the UL...
  3. che12345

    Regadring thermocouple sensor and calibration

    I have the following opinion for your consideration. 1. Transmitter is about 200 m would affect the accuracy. It is affected by besides the voltage drop, more importantly is by the electromagnetic interferences; switching and motor etc. Suggestion: Relocate the transmitter (which is of very...
  4. che12345

    IEC LV MCCs - Withdrawable starter units

    I may had misunderstood your question. 1. I had fabricated thousands of LV withdrawable system. It is standard design/practice that no (test supply) disconnections are required when the unit is to be put into the test position. In test position: a) the main power contacts shall be disconnected...
  5. che12345

    Standard for Maximum Lifespan

    1. Do you mean maximum or minimum? 2. What I understand the standard organizations are involved with the safety, on use of electricity and equipment i.e. motors, switchgear, and UPS systems etc., but not on the lifespan or recommended operational lifetime. Che Kuan Yau (Singapore)
  6. che12345

    Power Factor

    @ Mr FilipRST (Electrical) I notice some unusual data in your measurement. Please advise/clarify. 1. a) When no pump is running with 2 kW loading, the average voltage is 615 V, 6.67 A, pf 0.27..., b) When one pump is running with 27 kW loading, the average voltage is 617 V, 35 A, pf 0.72... 2...
  7. che12345

    Power Factor

    Thanks Mr stevenal Let us get it right. Following are examples on some common items: 1. KVAHrs should be kVAh. Attention: NOT KVAh, 2. KVARHrs should be kvarh. Attention: NOT kVArh, 3. KV should be kV . Attention: NOT kv, 4. CB 'trip time' 0.1 s, Attention: NOT 0.1 S, 5. BB 'contact resistance'...
  8. che12345

    Power Factor

    I have the following opinion. 1. In general, motor PF (kW/kVA) is ALWAYS low say (< 0.5) at low (< 0.4) loading. PF improves from say (> 0.70) say (> 0.8) loading. After that PF improves not very much from 0.8 to 1.00 loading. 2. Most LV supply from utility say < 500 A, do NOT penalize consumers...
  9. che12345

    Power Factor

    I have the following opinion for your consideration. 1. No pump is running P = 2 kW, P =0.27 Note: a) with 2 kW shows that there are some other loads, (e.g. lightings) with low PF. Power transformers lightly loaded or some (smaller?) motors which are lightly loaded etc. b) Many lighting...
  10. che12345

    ACB trips when the control power transfer from UPS A to UPS B

    'Wire your emergency stop in the circuit between the capacitor or other time delay circuit and the UV coil'. I have different opinion. Attention: this may defer between different OEMs, but the basic principle is usually the same. 1. The emergency stop , (if any) SHALL be wired directly to the...
  11. che12345

    ACB trips when the control power transfer from UPS A to UPS B

    @ Mr NickParker (Electrical)(OP)7 Oct 24 09:38 '.. whether there will be any issues with the stop push button (local or remote)... if I have implemented a time delay in the circuit during the transition period, when the operator presses the stop push button (either local or remote), do they need...
  12. che12345

    ACB trips when the control power transfer from UPS A to UPS B

    @ Mr NickParker (Electrical)(OP) I have the following opinion for your consideration. Check the ACB catalog, as it may defers between OEMs. 1. The time-delay device (from the same OEM) as the UV release may be adjustable say 0.5-.. s etc. It delays only the UV from dropping out. It does NOT...
  13. che12345

    Help changing direction electric phase 1 motor

    @ Mr GHawk3798 (Electrical)(OP)6 Oct 24 01:26 '..I purchased a machine from China and they must have wired up the motor wrong because the pulley wheel is running counterclockwise when I need to it to run clockwise to properly work the machine..' 1. Please show the connection on the name-plate...
  14. che12345

    VRLA batteries and gas detection requirements

    '..I wanted to inquire if there are any known requirements for gas detection meters for VRLA (valve-regulated lead-acid) batteries which are used in to serve data centres?..' I have the following opinion for your consideration. 1. In US where NEC prevails, see Art 480-8 (a), Ventilation . "...
  15. che12345

    ACB trips when the control power transfer from UPS A to UPS B

    '...There was one charging motor. When a breaker was to be closed, the motor would be installed (It was quick and easy, just two wing-nuts held it in place). The breaker would be charged if needed and then closed. The closing spring would be re-charged ready for another close if needed. The...
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