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19 Cards in this Set
- Front
- Back
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Is the relationship between load and slip proportional or inverse? |
Up (Slip) = Up (load) Proportional |
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1 hp = ??? Watts |
1 hp = 746 watts |
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What is the equation for torque? |
Torque = force [F] x radius [r]
T= Nm F=N r=m |
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What are the three types of mechanical loads? |
1: variable torque 2: Constant torque 3: constant horsepower |
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Name some variable torque loads |
Centrifugal pumps, centrifugal, compressors, centrifugal fans, and blowers |
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Name some constant torque loads |
Reciprocating compressor’s, crushers, positive displacement, pumps, conveyors, printing, presses, punch, presses, low-speed vehicles |
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Name some constant horsepower loads |
A small diameter material rotating quickly, lathes, drill press, milling machines |
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Name the three main parts of an induction motor? |
1. Frame 2. Stator 3. Rotor |
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What is the equation for synchronous speed? |
Back (Definition) |
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Where do NEMA motors have their junction boxes? |
On the right side viewed from the front (the front is the side without the shaft sticking out) |
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What are the two types of motor frames? |
Fractional horsepower and integral horsepower |
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Nema standard states that voltage V8 variations may not exceed plus or minus 10%, what does this mean? |
For a 3 phase motor all three legs:If the motor is rated for 120V then the maximum 132V voltage and the minimum is 108V |
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Name a standard states that the voltage variation for frequency may not exceed plus or minus 5%, what does this mean? |
57hz to 63hz is fine if the motor is rated for 60hz. |
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The maximum voltage on balance should not exceed 1%, what does this mean? |
If you measure; L1-L2 = 208V L2 -L3 = 210V L1-L3= 211V
Vavg= (208+210+211)/3 Vavg=209.99
Max deviation=209.66V-208V Max deviation=1.66V 1% of 209.66V is greater than 1.66V |
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If duty is not indicated on the nameplate, the motor is considered continuous duty true or false? |
True |
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What are some notable characteristics of Design A rotors? |
-Highest efficiency -150% FLA starting torque -suitable for most loads besides high-inertia loads (same as B) -not common because of high starting current (600%) -machine tools, fans |
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What are some notable characteristics of Design B rotors? |
-Starting current 500% FLA -most common -second most efficient -max breakdown torque of 200% -suitable for most loads besides high-inertia loads (same as A) -machine tools, fans |
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What are some notable characteristics of Design C rotors? |
-500% FLA starting current -starting torque of 225% -suitable for maximum torque = breakdown torque=starting torque -suitable for most loads besides (1)high-inertia (2) frequent starts (3) hard to start -loaded compressors, conveyors |
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What are some notable characteristics of Design D rotors? |
-low starting current -highest starting torque (275%) -low starting current -suitable for high-inertia, frequent starts, hard to start loads. -punch presses |
