[EL] 問﹕Motor Starting 有邊幾種方法？

答﹕

首先講點解要有Starting.

起摩打嗰陣，個back EMF 未建立，起動電流會好大，電流過大首先會過熱燒斷電線，仲有會忽然chur太多電令其他電器電流忽然少咗，輕則電燈會閃下，重則電腦都同你熄埋。

常見Motor Starting 方法有

1. Direct on line, 簡單嚟講即係乜都冇，直接點著個摩打。

2. Star - Delta

Star 接法 line current 細好多

但Delta接法 Line Current 就大一大截

所以有個做法，就係先起動個Main Contactor + Star Contactor起咗機先, 行一陣再用個timer 轉接過Delta Contactor, 咁就可以降低個Coil current. 不過同時起動個力同速度都會有所減弱

3. Autotransformer

逐級升Voltage嚟減少一開始既電流

4. Soft Starter

裡面主要有舊叫Triac既嘢嚟降低初始電壓

同DOL比較，要去到最終速度同電壓既時間都會耐咗

詳見﹕https://www.youtube.com/watch?v=6X71RZWvOvc

5. VFD

原理大概係先由一組Diode將AC轉做DC，再由Capacitor整波Filter, 最後由一組Transistor出返AC. 可由RS485控制

詳見﹕https://www.youtube.com/watch?v=g7jFGOn6xfU and https://www.youtube.com/watch?v=yEPe7RDtkgo&t=696s

Soft Starter 同 VFD 除咗原理唔同外，最大分別係前者平啲細舊啲，但冇得通過控制Frequency嚟控制速度

計數方面﹕

Direct on line - x 7

Star Delta - x 2.5

Autotransformer - x 2-3

VFD - x 2-3

詳見 https://www.youtube.com/watch?v=h89TTwlNnpY

(Source: The Engineering Mindset; Realpars)

[AC][EL][FS][PD] 問﹕各類型空間响BS Engineering Design上係要注意？

答﹕

Artium 中庭﹕Smoke Extraction, glass panel, OTTV Limit + natural lighting / tubular daylighting, ELV - audio / video / speakers, projection screens for performances or special events

Auditorium 劇院﹕Drencher System, beam detector + long throw sprinkler + Flame detector, smoke extraction, displacement ventilation (duct works underfloor, modulating volume control damper, plenum 1.5m/s, supply diffuser 0.15m/s), NC level 20-30, orchestra pit, stage lighting

Child Care 幼兒﹕IAQ, Natural lighting

Court Room: NC level 25-30, UPS, 1000 lux

Hotel: License from Home Affairs Department

Lobby: Air curtain

Mail Center: HEPA filter (HK有必要？)

Car Park: EV Charger, CO sensor, hydraulic lift, petrol interceptor

Physical Fitness: latent load, negative pressure

Plaza: Waterproof socket

Dangerous Goods: 

• Fixed Sprayer, Portable / Automatic Fire Extinguisher, Heat detector, Flammable gas detectors, 

• 5ACH, Elector-thermal link fire damper;

• Flameproof Fluoresent Luminaire, mineral insulated cables, explosion proof socket (唔係防爆炸，係防火花), 

• Ultrasonic level transmitter, flameproof emergency manual override to stop fuel pumping system, overflow / sensor, emergency oil cut

Underground Space: sump pump

Mortuary: Pathogens through Airborne particles from cadavers, 20ACH;

Natural lighting, sufficient for working and psycological 

Columbarium: 

License by FEHD, including 

FSD Vent/425, FSI 314, FS 251, FS 163 Dangerous goods, min. distance from 化寶爐;

EPD 化寶爐 smoke exhuast location and treatment; 

Septic tank 化糞池, Soakaway System (詳見﹕https://www.epd.gov.hk/epd/sites/default/files/epd/tc_chi/environmentinhk/water/guide_ref/files/guide_wpc_dv.pdf)

一啲偏遠冇污水渠既地方會用呢個方案，先經化糞池，再經滲水池將啲污水drain落泥度，化糞池裡面啲嘢就由泵車泵走。

Nosie Control

(Source: https://www.wbdg.org/space-types/atrium)

[AC] 問﹕Fume Cupboard Design 有啲乜要留意？

A.      Function of fume cupboard

-    To  remove  fumes  effectively  so  as  to  keep  the concentration of the contaminants  in the breathing zone of the operator to below the exposure  limits  and  also  to  prevent  the  build up of an explosive atmosphere inside the FC.

-    To place a physical barrier between users in the laboratory and the work inside the fume cupboard.

-    To provide an effective containment device and exhaust in case of accidental spills and emergency.

B.      Type of fume cupboard

-   Conventional fume cupboard

-    CAV (Constant air volume- when sash is lowered down, high face velocity ie Q=VA, turbulence occur, bypass with modulating valve should be added

-    VAV air volume, the exhaust air is controlled to maintain face velocity in preset value when the ash is partially closed.

-    Auxiliary air fume cupboards- same as conventional fume but add dedicated makeup, reduce energy loss of return air taken by fume cupboard. Exhaust venturi valve interlock with make up air to maintain negative pressure for the fume cupboard.

-    Re-circulatory or ductless fume cupboard- no direct exhaust to open air, independent exhaust and re-circulate by filter

-   Water supply point with drain

C.      Design checkpoint

-    Location: away from normal traffic pattern, cross-draughts, air inlets and other sources of disturbance, exit from a work space (may have potential risk of fire or explosion in fume cupboard)

-    Face velocity = 0.5m/s

(鳴謝﹕紅豆)

[AC] 問﹕Chiller 運作原理係點？有啲乜保護方法？

答﹕

理解咗個運作原理，要保護啲乜就容易理解得多，個chiller由四個主要部件組成，Compressor, Condensor, Expansion Valve, Evaporator; 當然，個compressor仲要有motor推動，同埋個system裡面要有refrigerant

又或者Youtube睇一轉

https://www.youtube.com/watch?v=K0xAKzdROEg

個Chiller最頂嗰舊係Compressor, 低一倉係Evaporator, 最低嗰倉係Condensr

Condenser: 

High / Low Return Condenser water temperature / Reduction of water flow in condenser (Water Cooled) / Reduction of air flow in condenser (Air Cooled) / High / Low Ambient Air Temperature (Air Cooled)

If no flow signal, the pump will automatically interlocked for changeover to the standby pump.

Evaporator:

Evaporator Low Cut / Low flow 

Expansion Valve:

Blocked expansion valve

Compressor:

Oil: Lubrication Oil Level / Oil Pressure

Electrical: Motor, VSD, Panel High Cut / Over Current / Votage High, Low / 3 phase unbalance / Surge Protection

Refrigerant:

Purge for non condensable in refrigerant loop / System Pressure 

(鳴謝﹕紅豆、K、諾克Sir; Source: https://youtu.be/Zu0LVVNNVSw ; https://www.youtube.com/watch?v=K0xAKzdROEg)

[EL] 問﹕球場 Football Field / Stadium Lighting Design 有啲乜要注意？

答﹕

FIFA (國際足盟大賽)，UEFA(歐洲冠軍聯賽) 標準

Class I (Amateur 業餘) 

- 200 lux, 0.5 uniformity

Class II (Semi Professional)

- 500 lux, 0.6 uniformity

Class III (Professional Stadium)

- 750 lux, 0.7 uniformity

不過上述都唔足以做TV broadcasting, 大概要滿足以下條件先做到

- 1000-1500 lux, uiformity U1 0.6, U2 0.8, Colour Rendering Index 70 以上(0-100Ra)

- Floodlight Luminaire Mounting: 

原則﹕唔好比影擋到，大概25-30m

兩側﹕光到達球場中心嗰點要响25°同45°之間

Goal line: 

45°同60°之間

(鳴謝﹕諾克Sir; Source: https://www.ledsuniverse.com/football-field-lighting-standards-and-regulations/; 

UEFA Stadium Lighting Guide 2016 https://www.uefa.com/MultimediaFiles/Download/uefaorg/General/02/36/26/72/2362672_DOWNLOAD.pdf)