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Published byApril Laura Foster Modified over 8 years ago
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-Basic Circuits -Power Distribution -Fusing/Protection
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Closed Circuit
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Open Circuit
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Switch
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Short Circuit
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Normally Open Circuit = open when non-energized and closed when energized Normally Closed Circuit = closed when non-energized and open when energized Normalcy = no electric/ non-energized
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100,000’s volts 100,000,s volts Reduces to thousands 240 volts 12,000 volts harder hall
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Transformers -changes voltage P=primary S=secondary Example: 240volt (P) to 24volt (S) 10 to 1 ratio
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Power lines Transformer Service wires Service entrance panel Breakers Disconnect box Receptacle
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AWG (American Wire Gauge) Amps 00145 0125 1110 295 380 470 655 840 1030 1220 1415
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Walter de Maria’s The Lightening Field
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Richard BoxLight Fields
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Series Curcuit Rt = R1 + R2 + R3
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Parallel Circuit RT= 1 OR if resisters are same, divide the ohms of one leg by the # 1/R1 +1/R2 + 1/R3 of resister RT = ohms/3
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Series Parallel Circuit
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Phases Single Phase Three Phase (sine wave)
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Delta (3 wire system) Wye ( 4 wire system )
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Lets wire: from service panel - 120v receptacle 240v receptacle
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Lets wire: From 208 three phase panel - 120v receptacle 208v receptacle
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End of 3
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Designing for Heat
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Volume of ChamberKW RequiredKW increased per C FT 1 c ft3 2 c ft4.52.5 3 c ft6.52.0 4 c ft8.01.5 5 c ft9.251.25 6 c ft10.51.25 8 c ft12.751.125 10 c ft14.51.125 Electric Kiln Construction for the Potter, Robert Fournier Table # 6 Power/volume Relationship Find - Watts per cubic ft ? - Watts per cubic inch
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2’ x2’ x 2’ Hot-Face 8 c ft = 12750 total watts Watts / cubic ft= Watts / cubic inch = Watts/ square ft= Watts/square inch=
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As a general rule: 1 watt / cubic inch (Assuming it’s insulated well) -Cubic inch = -Watts needed= I,D 24” 20”
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-@ 240 v Amps= -Let include some margin of error, Amps -Size wire needed from panel AWG -Size breaker needed Electrical panel= I,D 24” 20”
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AWG (American Wire Gauge) Amps 00145 0125 1110 295 380 470 655 840 1030 1220 1415
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Ohms Law= Network Resistance= ohms Lets look at Kenthal A-1 Tables Lets use 14 gauge The value given is.2124 ohms/foot I,D 24” 20”
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The value given is.2124 ohms/foot We need ohms Each foot has.2124 Ohms needed = Feet of wire.2124 I,D 24” 20”
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25 feet of A-1 wire around a 3/8 mandrel would be about 10” long If we connect to 240volts This gives us 40 amps or 9600 watts. This element may heat for a matter of seconds before it burns up. Wait a Minute!!!!! I,D 24” 20”
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Why? A-1 Data Table: Find - sq in / ft 14 gauge wire Sq. inches per foot x feet of wire = total sq inches Surface Loading table : Total watts Total sq in = watts/ sq in
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We need to use more wire to increase the surface area, but we need to keep our 5.33 ohm Network Resistance Lets go back to Series Parallel Circuits : RT= 1 OR if resisters are same, divide ohms of one leg by the # of 1/R1 +1/R2 resisters RT = ohms/3
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Calculate the surface load with our 5.33 N.R. : Lets say: Ohms needed 13.32 = Feet of wire.2124 Sq. inches per foot x feet of wire = total sq inches 2.412 x = 1. 2. Total watts Total sq in = watts/ sq in Look to Chart Total Sq inches x 4 Elements = sq inches x 4 = 3.
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Total # of elements= 1 st, lets look at how many elements we can fit into the walls and floor.
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Lets try (10) 13.32 ohm elements. Perhaps the following Series-Parallel circuit will work: 5 elements in parallel: 5.33 x 5 = ohms Because we have 2 elements in series : ohms / 2 = ohms Network Resistance=
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Calculate the surface load with our 5.33 N.R. : Ohms needed 13.32 = Feet of wire.2124 Sq. inches per foot x feet of wire = total sq inches 2.412 x = 1. 2. Total watts Total sq in = watts/ sq in Look to Chart Total Sq inches x 10 Elements = sq inches x 10 = 3. 4.
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Coiled length @ 1 ohm = 2” = Stretched length = Feet of wire used Feet of wire = Ohms needed x # of elements.2124 Money spent on wire Cost of spool Feet in spool = cost/ft x total feet used= $
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g Kenthal A-1
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Control loops
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Super-Super-Duper Basic Kiln 120 volts Extension Cord 16 ohm Heating Element Current? Power?
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Super-Duper Basic Kiln 240 volts Extension Cord 20 ohm Heating Element Current? Power?
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Lets start to control rate of temp. Infinite control switch Bimetal switch Good for switching on and off up to 15 amps
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Lets add a kiln sitter Kiln sitter good for up to 50 amps
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If we go over 50 amps or would like to use a computer controller Lets add a mechanical contactor ( Relay )
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Simplified 3 zones 240v ac
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Lets wire our Bartlett controller: 240v 1 zone
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