Any value greater 0.5 ohms indicate trouble with the motor. A good motor should read less than 0.5 ohms. With a multimeter, measure the resistance between motor frame (body) and earth. Examine the name plate thoroughly and compare values of running amps test (see below) with name plate value (3) As with all testing and inspections, the motor name plate provides valuable information that will help to ascertain the true health of the motor. If shaft rotation is free and smooth, bearing is possibly in good condition, otherwise consider replacing, repair or carry out further diagnosis. Look out for smooth and free shaft rotation. (2) Manually rotate motor shaft to examine bearing condition. Check for burnt, damage to body or cooling fan or shaft.
Just beware that from 230meg to 600meg often shows some deterioration in the cables or motor insulation.The basic steps in ascertaining the health of a three-phase AC motor are given below:įor the three-phase motor, do the following: Though 230meg for a 230VAC circuit seems on the low side from my experience. A rule of thumb that I've come across in other reference materials is about 1000 ohms of resistance for each volt of incoming power. The above is what I found to be the average for 230VAC 3 phase motors. It can give false and unrepeatable readings causing you to chase your tale. Be careful not to touch the leads or the wires to anything when taking the reading. Readings are usually in a range from 600-2000 Megohms.
Check all three wires separately T1,T2,T3 (all three phases) to the ground wire. Make sure you use quality meter going up to at least 10megohmsĭisconnect all power from machine. Most servo motor shorts can be read with a regular quality meter.
Be sure to make sure leads on both ends are not touching anything including the other leads. If it is go directly to the motor and disconnect from cable and check motor and the cable separately. If its zero or reads any continuityĪt all, then a problem exists with either the motor or cable. Check all three wires singly T1,T2,T3 (all three phases) to the ground wire. Check the cable along with the motor at the same time to cover everything, if this turns out good then all is usually well. But before starting turn off all power sources to machine then disconnect the 3- phase motor lines ONLY from the drive. This procedure will show you how to test for shorts in windings, cables or opens. Below are some basic principles for testing servo motor circuits with meter or megohm meter.
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