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PostPosted: February 24th, 2009, 11:27 pm 
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I am rebuilding an older 1236 McElroy machine (1977) and I am looking for the DC power requirements for the machine, what generator is required? It is the mine model, 460V 3 Phase and the generator supplier says he needs to know the total amperes required. Could you let me know?


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PostPosted: February 25th, 2009, 10:10 am 
This machine was origanally built with a 10hp, 3 Phase, 60Hz 230 volt motor. The Heater at 20KW for 12"-36" pipe. With this the Minimum generator requirement is 30KVA, 230 Volt, 3 Phase, 60HZ.


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PostPosted: February 25th, 2009, 3:03 pm 
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Everything you mentioned is correct, 10HP, 3 phase,60 Hz, except the voltage is 460V 3 Phase which McElroy build to mining standards. This still does not answer my question about ampere requirements.


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PostPosted: February 26th, 2009, 11:42 am 
*if* its a 460V 20kW heater (should be confirmed on a schematic), i get:

for a resistive only 3 phase load:
Power = Voltage * amperage * 3^0.5

solve for amps

20,000W / (460V * 3^0.5) = 25.1A for the heater

for motor I get
10HP*746W/HP*1/0.8 (power factor guess) * 1/0.88 (efficiency guess)=10.6kW

since

(3^.5 * motor voltage * full load amps (FLA) ) = Power

FLA = 10600W/(460V*3^0.5) = 13.3A

so if the premise is true about heater power, the maximum amperage would be 25.1 + 13.3 = approx 38A.


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