Electrician Red Seal · Question
A three-phase squirrel-cage induction motor is operating normally. If one of the supply phases opens while the motor is running, what is the most likely immediate effect on the motor?
If a three-phase motor loses one phase while running, it will continue to operate as a single-phase motor, but with reduced torque and increased current in the
Start free practice for Electrician Red Seal
150 questions · no signup required · 40 free questions per day
Question: A three-phase squirrel-cage induction motor is operating normally. If one of the supply phases opens while the motor is running, what is the most likely immediate effect on the motor?
Answer options: ✅ The motor will continue to run but at a reduced speed and with increased current in the remaining phases.
- The motor will immediately stop due to loss of torque.
- The motor will draw excessive current and quickly trip its overcurrent protection.
- The motor will run in reverse direction.
Correct answer: The motor will continue to run but at a reduced speed and with increased current in the remaining phases.
Explanation: If a three-phase motor loses one phase while running, it will continue to operate as a single-phase motor, but with reduced torque and increased current in the remaining two phases, leading to overheating if not protected. It will not immediately stop unless heavily loaded, nor will it run in reverse.
Start free practice for Electrician Red Seal
150 questions · no signup required · 40 free questions per day
More about Electrician Red Seal
Related Questions
- A residential garage is to be wired with a 15 A, 120 V duplex receptacle. According to the Canadian Electrical
- During a renovation of a commercial kitchen, an electrician needs to replace an old single-phase, 240 V, 5 kW
- A commercial kitchen is being renovated, and several new 4 kW, 208 V, single-phase electric ovens are being in
- What is the minimum working space depth required in front of an electrical panel rated 200 A, 120/240 V, locat
- A Red Seal electrician is setting up temporary power for a construction site. The main temporary service is a
- A new industrial facility requires a 600 V, three-phase, 150 A feeder to supply a motor control centre. The co
More for Electrician Red Seal candidates
Practice tests
Question explanations
- A residential garage is to be wired with a 15 A, 120 V duplex receptacle. According to the Canadian Electrical
- During a renovation of a commercial kitchen, an electrician needs to replace an old single-phase, 240 V, 5 kW
- A commercial kitchen is being renovated, and several new 4 kW, 208 V, single-phase electric ovens are being in
- What is the minimum working space depth required in front of an electrical panel rated 200 A, 120/240 V, locat
Ready to practice?
Free, no signup required. Build a wrong-question list as you go.
Start Free Electrician Red Seal Practice →Related courses
Other Canadian certifications candidates often prepare for alongside this one.