Three-Phase Motor Testing Procedures (Physical And Electrical Tests)

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When you test a three-phase motor, you check the mechanical and electrical aspects of the engine to determine its condition. To guarantee that the motor has been thoroughly examined, you will need to carry out a variety of tests, each of which has its specific protocol.

In this instruction manual, we have provided various checks and tests that will examine and test the motor both mechanically and electronically. An individual knowledgeable in electricity and mechanics ought to carry out the tests at all times.

The following tests will be looked at:

  • A physical check of the motor
  • A look at the motor in person
  • Test of Earth’s stability and resistance
  • Checking the supply coming in
  • Continuity of motor windings
  • The test for motor winding resistance
  • Test for insulation resistance
  • Complete load amp (FLA) test

By doing these tests, we can locate the location of a malfunction on a three-phase electrical motor and assess its overall condition. When a motor has failed, or its state is being evaluated, a qualified electrician should perform the below tests.

How to check out a three-phase motor physically.

When evaluating a three-phase motor, the physical condition of the motor should be the initial test conducted. This will inspect the state of the motor’s shaft, cooling fan, and main body. When visually inspecting any motor component, the power should be isolated and unplugged from the source whenever possible.

  • With the motor cut off, you should try to turn it by hand. If this is easy to do, it shows that the bearings in the motor are in good shape. If the motor is hard to turn, it means there is a problem with how it works. The directions or shaft may have broken.
  • Another test is to look at the body of the motor, the shaft, and the cooling fan to see how they look. First, look outside the motor to see any signs of cracks, corrosion, or damage.
  •  The next thing to check is the shaft of the motor. This is easier when the motor is not connected to the coupling or other mechanical parts. You should ensure the post is in good shape and has no significant wear, cracks, or damage.
  • The cooling fan and the housing for the cooling fan should be the last things to look at. You can check the cooling fan by taking off the case, which is usually held on by a few screws. You should ensure that none of the fan’s blades have any cracks or rust. The housing for the cooling fan should also be checked for cracks, corrosion, or damage that is easy to see.

How to Conduct a Test for Earth Continuity and Resistance

It would be best if you used a multimeter to check the resistance between the body of the three-phase motor and the ground.

  • The reading should be less than 0.5 Ohms if the motor works well.
  • If it goes higher than this, it could mean a problem with the motor’s earthing.

The earth continuity test is essential to ensuring that the three-phase motor is safe and working well.

When you test a three-phase motor, you check the mechanical and electrical aspects of the engine to determine its condition. To guarantee that the motor has been thoroughly examined, you will need to carry out a variety of tests, each of which has its specific protocol.

In this instruction manual, we have provided various checks and tests that will examine and test the motor both mechanically and electronically. An individual knowledgeable in electricity and mechanics ought to carry out the tests at all times.

 

Photo Credit: Engineerfix.com

Methods For Verifying Incoming Supply

You should always check the level of the power coming in and make sure it fits the motor’s operating voltage. Different motors need different amounts of voltage, which can be AC or DC.

  • You should see 230V between the three phases (U, V, or W) and the neutral on a three-phase motor. If you test phase to phase (U to V, U to W, or V to W), you should get about 400V.
  • Use your multimeter to make sure that the proper supply is there.
  • Make sure this is done safely and with the proper testing equipment.
  • This will be different in each country. Check out our article on input voltage for more information.
Photo Credit: Engineerfix.com

How To Conduct A Winding Continuity Test On A Motor

You should use a multimeter to check if each motor phase is still connected. This will let you check the condition of each winding and make sure none of them are burned out.

  • To test for continuity in a motor winding, set the multimeter to the continuity setting and check from phase to phase (U to V, U to W, and V to W).
  • Depending on your type of multimeter, your meter should beep or show a connection between phases.

This proves that the motor isn’t breaking from the inside out and that good connections are still being made. Having good readings on continuity tests is critical to motor performance and efficiency.

Photo Credit: Engineerfix.com

How To Carry Out A Test On The Winding Resistance Of A Motor

Check the resistance between the three terminals with a multimeter. These are the U, V, and W terminals.

Photo Credit: Engineerfix.com
  • In three-phase motors, the measurements between each winding should be approximately equivalent.
  • Each of the three windings is identical, so the resistance between them should be nearly identical.
  • There will be little variations in the levels, but you’re searching for significant discrepancies.

Any significant deviations from the above characteristics would indicate that the motor has electrically failed and has to be repaired or replaced.

How To Conduct An Insulation Resistance Evaluation

  • The voltage on an insulation resistance tester or megger should be set to 500V.
  • Insulation resistance is measured between the motor’s phases and the ground.
  • Check all earth phases (U to Earth, V to Earth, and W to Earth). After this, you should check phase to phase as well (U to V, U to W, or V to W)
  • The minimum value for a quality motor is approximately 1M – minimum.

Instructions on How to Carry Out an Amp Test

You must test the motor’s total load amps using a clamp or appropriate meter. The total load amps (FLA) can be found on the motor’s nameplate, which is typically positioned on the motor’s body. Any significant divergence from this would indicate a motor malfunction.

  • When doing an amp test, the motor should always be running, and things should be standard.
  • You should clamp the meter around one phase of the motor’s power cable to do the test.
  • Check that the reading is close to the number of amps shown on the motor’s nameplate when the motor is under full load.

One example is a conveyor belt with a slope that could be used to move meat products. When the product is on the conveyor belt, the load on the motor will be higher than when there is nothing on the conveyor. You get a more authentic and accurate reading when you test under normal conditions.