Which of the abnormality is possible in a three-phase induction motor?
The main types of external faults experienced by an induction motor are over-loading, single phasing, unbalanced supply voltage, locked rotor, phase reversal, ground faults, and under/over voltage.
Which abnormality is possible in induction motor?
External factors that may cause abnormal operation of the induction motor are: 1. Poor voltage quality, such as sags or unbalance. As already explained in Section 2.4, voltage sags result in quadratic reduction of the developed torque, so that the motor may stall.
Which of the following faults will a three-phase motor overload protect against?
These protection relays disconnect the motors when they detect a fault that can cause damage. An overload is a condition in which the motor currents (or power) are above the nominal values. Unlike a short circuit, overloads may be of just a few amperes over the rated current.
What type of motor protection would be found for a 3 phase motor?
1. Per NEC® 430.37, three-phase motors must have an overload protective device in each phase. Use motor overload protection such as overload relays/heater elements in each phase of the motor. Prior to 1971, only two overload protective devices were required and motors were much more susceptible to motor burnout.
What are the three classifications of electrical problems?
There are mainly three types namely line to ground (L-G), line to line (L-L) and double line to ground (LL-G) faults.
What are mechanical abnormal conditions of induction motor?
Induction motor abnormalities due to external factor are influenced by the input of power quality. Such external abnormalities considered in this analysis are over voltage, single phasing, under voltage, voltage unbalance. All the above abnormalities affect the motor performance and reduce the motors lifetime.
What is difference between overload and overcurrent?
ANSWER: Overcurrent protection is protection against excessive currents or current beyond the acceptable current rating of equipment. It generally operates instantly. … Overload protection is a protection against a running overcurrent that would cause overheating of the protected equipment.
What causes a motor to overload?
Electrical overload or over-current is caused by an excessive current flow within the motor windings, exceeding the design current which the motor is able to carry efficiently and safely. This can be caused by a low supply voltage, resulting in the motor drawing in more current in an attempt to maintain its torque.
How do you check motor overload?
Overload Protection Test:
- Measure the normal motor running current (i motor).
- Turn off the motor and let it cool for about 10 minutes.
- Calculate the following ratio: i (motor) / i (overload min FLA). …
- Set the overload to its minimum FLA and turn on the motor.
- Wait for the overload to trip.