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7 Cards in this Set
- Front
- Back
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Across the line start Starting characteristics? Volts? Line current? Starting Torque? |
Starting characteristics Volts: 100% Line current: 100% Starting Torque: 100% Advantage: inexpensive, simple to maintain, maximum starting torque Disadvantage: High inrush current |
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What do you need to do a part winding start? |
A dual voltage motor Less than 1second on part winding. No more than 5 seconds because of overheating of the motor |
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Primary Resistor Starting
Starting characteristics? Volts? Line current? Starting Torque? |
Used to be called a choke coil to limit speed… used on a condenser fan to increase head pressure.
Resistor in series with coil limits voltage to motor windings.
Starting characteristics? Volts? 65% Line current? 65% Starting Torque? 42% Advantages: smooth acceleration, high power factor during start, leas expensive than autotransformer, available with multiple speed points. Disadvantages: Low torque efficiency, resistors must be cooled, starting times longer than 5 seconds require expensive resistors, doesnt work well with varying torque conditions. Resistors use energy! |
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What is the difference between a motor starter and a contactor? |
Motor starter has the option to have an overload built in. |
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Open transition? |
(1)Starts at lower speed (2) Power removed and (3) reapplied to full speed. Basically power is on, off, on… and remains turning the whole time! |
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Auto transformer start |
Starting characteristics Volts: 65% Line current: 42% Starting Torque: 42%
Advantages (1)highest starting torque (2) different starting torques are selected (3)suited for long starting periods
the autotransformer to permit the user to start the motor at approximately 50%, 65%, or 80% of full line voltage.
Disadvantage (1) open transition has more electrical “noise” (2) low power factor (3) large physical size (4) power falls to zero during open transition
If you leave the autotransformer connected and run the motor continuously. Volts: 80% Line current: 64% Starting Torque: 64% |
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Closed transition |
The motor is not disconnected from the line line. |
