androidjae.blogg.se - Motor winding resistance test

Leaking coil to ground (current leaking from one coil to ground/neutral).

Short-circuited coil (less than normal or zero coil resistance).

There are basically 4 problems that the motor windings can suffer from: If someone works with AC 3-phase motors, then it is important to know how to connect these motors in Star and Delta connection, and how to detect an electrical problem. It is called squirrel-cage, because it's rotor looks like the exercising wheel found in squirrel or hamster cages.Ī typical 3-phase squirrel-cage motor has six connection leads in the electrical connection box for the three coils. The most common type though is the -so called- squirrel cage rotor. The locked rotor method is probably easier to setup but the dynamic test will give you better repeatability.The rotor of a squirrel-cage motorThere are several different AC motor types, each one with different operating and mechanical characteristics.

Repeat this test by either switching the lead wires or switching the direction of rotation of the back-driven motor. While the motor is being back-driven, apply a voltage to the terminals (again, until the current reads 25% of rated full load current). This method requires you to back drive your test motor at a slow speed. The second method requires only 2 measurements but it is a little more complicated test setup. Repeat this a number of times at different locked rotor positions and then take the average resistance. Using that voltage and current, determine resistance using Ohm's Law. You increase the voltage until the current is at 25% of the rated full load current. There are 2 ways to measure terminal resistance.įirst, you can lock the rotor of the motor and apply voltage to the terminals. You mention that you are measuring "internal resistance" which is often exclusive of the lead wires and brushes (i.e., it is measured from bar to bar on the armature). You should be measuring terminal resistance (resistance from one lead wire to the other lead wire) for IR compensation.