Check the motor winding resistance or ohms reading using a multimeter or ohmmeter for phase to phase terminal ( U to V,V to W ,W to U ). The ohms reading for each winding must be the same (or nearly the same). Remember that the three phases have identical windings or nearly so!
How do you know if a 3 phase motor is bad?
Check all three wires singly T1,T2,T3 (all three phases) to the ground wire. Readings should be infinite. If its zero or reads any continuity at all, then a problem exists with either the motor or cable . If it is go directly to the motor and disconnect from cable and check motor and the cable separately.
How do you know if motor winding is good or bad?
With a multimeter set to low ohms (usually 200), test between each winding terminal and the metal casing of the motor. If there is any reading on any of these then the motor is bad, do not use it. You may find that when it runs ungrounded that the casing becomes live at up to supply voltage.
Should a 3 phase motor have continuity?
The windings (all three in a three-phase motor) should read low but not zero ohms. … It will usually be low enough (under 30 Ω) for the audible continuity indicator to sound. For proper motor operation, all windings must have megohm readings to ground, i.e. to the motor enclosure.
How do you check motor windings with a multimeter?
Inspect the Motor Windings With a Multimeter
To begin, set the multimeter to read ohms and then test the motor’s wires and terminal. You should test the windings for a “short to ground” in the circuit and open or shorts in the windings.
How many ohms should a 3 phase motor read?
The reading should be between 0.3 to 2 ohms. If it is 0, there is a short. If it is over 2 ohms or infinite, there is an open. You can also dry the connector and retest to possibly get more accurate results.
How far apart are the windings of a three-phase motor?
In a three-phase alternator, there are three windings placed 120° apart from each other. A three-phase balanced winding in the stator of the alternator is shown in the schematic diagram given below.
How do you find the insulation resistance of a 3 phase motor?
Phase Resistance: Take the insulation tester and set it to 500V. Take each end and place it on different permutations of L1, L2 and L3 and record each reading. Phase to Earth Resistance: Take the insulation tester, using the same setting, and check each lead from phase to the frame of the motor.
How many degrees apart are the windings of a three-phase motor?
The rotating magnetic field is produced by the three-phase current of the stator in the actual three-phase induction motor. It can be replaced by permanent magnets in a permanent magnet synchronous motor. The three-phase windings of the inner stator are spaced 120° electrical degrees apart.
How do motor windings fail?
Electrical failures disrupt the power supply to the motor. This includes single-phased winding failures (wye- or delta-connected) caused by an opening from a blown fuse, open contactor, broken power line or bad connection. Insulation failures are typically caused by contaminants, abrasion, vibration, or voltage surge.