Motor Terminals - Start and End Points

When I first saw this question from Anonymous I was tempted to advise the poster to look for the terminal box, open the cover and 'Voila!' the leads have been found!

My second thought was to advise the OP to make use of the CR4 search engine and so before making that recommendation I tried to carry out the search myself but found the search to be rather confusing in that, although the answers to the questions can be found there, it is a difficult process locating the right answers or even using the correct search criteria.

I know that I have answered this question before and was lucky enough to receive GA for the answer but was unable to locate that posting so I'll try to answer Anonymous's present query:-

1. Using your multi-meter on the Ohms range identify the thrDCee sets of windings and mark the ends of these windings A - A1, B - B1, C - C1.

2. Note the resistance of each winding.

3. Check that there is no connection (open circuit) between the three windings - A to B, A to C, B to C.

You now have two methods of identifying the start and ending of each coil -

Method 1 - Flick test using a 1,5v torch battery and an Analogue meter set to the lowest DC volts range.

a) Connect the negative side of the torch battery to the first winding end marked 'A'. Now just flick the other end of the winding 'A1' against the negative terminal of the torch battery and observe which direction the needle deflects (up or down).

Now repeat the same procedure for the other two windings noting the direction of the meter needle deflection.

If all three readings are the same then the three windings have been marked correctly.

If however two readings are the same needle deflection direction and one is in the opposite direction then that winding is incorrectly connected - swap the markings on the wire ends of that winding and then repeat the test - all three windings should give the same needle deflection on the meter.

You have now identified the three windings A, B & C plus the start and end of each winding A (start) & A1 (end) etc.

Method 2 - Measuring the voltage drop across each winding.

A) Connect the three windings in series i.e. by joining A1 to B and B1 to C.

B) Now connect a single phase AC voltage (below the nameplate operating voltage of the motor) across the motor windings - Phase to 'A' and Neutral to 'C1'.

C) Set your multi-meter to measure AC volts and switch on the supply that you have connected across the windings. Measure the voltage across each winding i.e. A to A1, B to B1 and C to C1. All three readings should be the same, but if one reading is different then that winding is connected in reverse. Reverse the connection to that winding and retest.

If all three readings were the same then your winding then the windings were all connected in the correct 'direction' and you have identified the start & end of each winding.

Good Luck! If you make other posts on this site please include more detail which will enable other members to assist you.

Regards, Keith