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17 Cards in this Set
- Front
- Back
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What formula do you use to calculate line current in a motor |
Input power/square root of 3 x voltage of load x pf |
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How do you calculate pf in a motor |
Pf= cos plus the phase angle Or P/S in the motor triangle |
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How do you calculate slip speed |
Synchronous speed x slip % |
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What is a BJT in terms of semi conductors |
Bi-polar junction transistor |
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What earth fault loop tests need to be carried out |
Tests to ensure protection final sub operates in required time |
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Why is the resistance of the protective earthing conductor of a flexible cord on a class on appliance set to a maximum of 1Ohm |
• under fault conditions, it prevents the touch voltages rising to a danger level • to ensure sufficient fault current flows to operate protective devices |
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Define the term cut off characteristic |
This is the value of fault current that cuts off the fuse that is less than the perspective short circuit current |
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Define the term total clearing time |
This is the time it takes to interrupt the flow of current and extinguish the arc |
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Formula for calculating line current in a transformer |
VA/ square root of 3 x line voltage |
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Define the term cut off characteristic |
This is the value of fault current that cuts off the fuse that is less than the perspective short circuit current |
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Define the term total clearing time |
This is the time it takes to interrupt the flow of current and extinguish the arc |
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Formula for calculating line current in a transformer |
VA/ square root of 3 x line voltage |
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Define the term cut off characteristic |
This is the value of fault current that cuts off the fuse that is less than the perspective short circuit current |
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Define the term total clearing time |
This is the time it takes to interrupt the flow of current and extinguish the arc |
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Formula for calculating line current in a transformer |
VA/ square root of 3 x line voltage |
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Why is the earth fault loop impedance test carried out at the socket furthest away from the switchboard |
• to confirm that the electrical protection will operate in required time •to confirm that electrical protection on all other final sub circuits supplied from the main switchboard will operate in required time |
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How do you calculate KW |
KW = VA / of |
