Three-Phase Motors And Starters Flashcards
When induction motors are connected in a positive phase sequence, the motor rotation is ___________ when viewed from the drive end.
Clockwise
Dual voltage motors have ____ leads
12; However only leads T1 to T9 are brought out of the connection box.
Dual-voltage 3-Phase, single speed motors are labelled ___/___V.
230/460V
How can the direction of rotation be changed on a three phase induction motor?
Interchange any two supply leads.
Dual voltage motors have ___ windings or groups of windings.
Six; two windings or groups for each phase.
What is the most common starting method?
Across the line full voltage start
List the terminal markings on a motor using a part winding start:
T1, T2, T3, T7, T8, T9
List the terminal markings on a motor using a wye-delta start:
T1, T2, T3, T4, T5, T6
What is the purpose of a reduced-voltage starter?
To reduce the inrush starting current on a motor circuit
A six lead wye-delta motor and starter has line voltage between terminals T1 and T2 during starting and running.
True or False?
True
List two starting modes common on electronic soft starters
Ramp Starting
Current limiting starting
Reduced-voltage starters also reduce _______ ________.
Starting torque
List five advantages of using a 15 hp, three phase motor over a single phase motor of the same rating.
- Lower cost for the motor
- More readily available
- More efficient
- Smaller for the same HP
- Quieter running
The two types of phase convertors are:
Rotary and Static
Voltages and phase displacements of _______ phase convertors are more balanced and can supply several motors.
Rotary
