Aux 2 Unit 4 Star and Delta Flashcards

How does the speed of a 3-phase motor connected in Delta compare to that of the same motor connected in Star?

C) Both connections provide the same speed

Which type of application would most likely require a motor with a STAR/DELTA starter?

B) A high-capacity industrial pump

Why is the motor configuration changed from STAR to DELTA after startup?

B) To provide full line voltage across each winding for maximum power and torque

What happens to the phase voltage when the motor configuration is switched from STAR to DELTA?

C) It increases to full line voltage

How would the windings of an a.c. motor be connected in a Star configuration?

B) Each winding is connected to a common neutral point, and the free ends are connected to the power supply

What is the relationship between phase voltage and line voltage in a Star connection?

C) Line voltage is √3 times the phase voltage

What would likely happen if a motor designed to run in Delta configuration is mistakenly connected in Star?

C) The motor would produce reduced torque and may fail to start heavy loads

Which of the following best describes a Delta connection in a 3-phase motor?

B) The end of one phase is connected to the start of the next, forming a closed loop

What is the relationship between phase voltage and line voltage in a Delta connection?

A) Phase voltage equals line voltage

Why would a motor connected in Star instead of Delta produce lower torque?

B) Because the phase voltage applied to the windings is reduced

What is the primary reason for using a STAR configuration during motor startup?

B) To reduce the starting current and torque, protecting the electrical network

What is the effect on phase voltage in a Star configuration?

C) Phase voltage is √3 times less than the line voltage

What is the phase voltage in a Delta connection relative to the line voltage?

B) Phase voltage equals the line voltage

What is the advantage of running a motor in a Delta connection compared to Star?

B) Higher starting torque

Which of the following best describes a Star connection in a 3-phase motor?

A) All three phases share a common neutral point

Under what conditions is a STAR/DELTA starter typically required for an induction motor?

B) When the motor needs to start with reduced current and torque

How does a STAR/DELTA starter operate during motor startup?

B) It starts the motor in STAR configuration for reduced voltage, then switches to DELTA for full voltage

What is the potential consequence of connecting a motor in Star instead of Delta when it is under load?

C) It may fail to start or run with reduced performance

How would the windings of an a.c. motor be connected in a Delta configuration?

A) The ends of each winding are connected to form a closed loop with no common point

Why might a direct-on-line (DOL) starter not be suitable for some large motors?

B) It creates high starting current and torque, which could damage electrical systems

Which of the following describes how the terminal links should be connected to configure a motor in permanent Delta mode?

A) Connect terminals U1 to V2, V1 to W2, and W1 to U2

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