Beginners Guide To Phase Rotation Tester

To understand the working principle of a phase rotation tester, first we must explain a few terms. First, for detecting the sequence of the supply in a 3 phase voltages, we use a phase rotation tester. A phase sequence is designed as the sequence in which three phase voltages attain their positive maximum values.

The three phases can be taken as red, blue and green. Now, there is a positive and a negative sequence. If, you take Red, Blue and Green phases, in this order the sequence can be taken as RBG, with R attaining its maximum value first. Like this, with B following R, and G following B, you have a positive sequence, and in the reverse order, RGB, you have a negative sequence. The difference here is in the direction the supply goes, in the first case is clockwise, in the second one is counter clockwise.


The phase rotation tester is used to detect the phase sequence in these three phase circuits. There are two basic types of phase rotation tester:

1. rotating type
   
2. static type

The rotating type functions similarly to a three phase motor. It works on the same principle as induction motors. For this example, let's assume that this phase rotation tester works on an RBG phase sequence, meaning clockwise rotation. If the opposite happens, in an RGB phase sequence, the supply will be counter-clockwise just like the motor rotation and a severe damage to the motor could happen.
When a three-phase supply is given to the coils, these produce a magnetic field, which produces eddy EMF in the rotational aluminium disk. A current is produced on the aluminum disk by the eddies, and then a torque, which causes the aluminium disk to rotate.


The static type works similarly to the rotating one and is more based on the counter-clockwise supply sequence. Here you have a capacitor instead of an inductor, and two resistors that are connected in series with lamps to protect them from eventual overcurrents or breakdown voltages.



It's important to pay great attention when using the phase rotation tester; you should understand how they work before energizing electrical motors and other equipment, as any mistakes in that procedure can cause you irreversible damage.