Rewinding a Brushless Motor

Introduction

If you fly brushless you've probably cooked a motor or two. You also probably know there are many different types of motors. Similar motors when wound differently performs very differently. Whether you've burned the motor up, or just want to alter performance, rewinding is a cheap solution for a patient modeller.

Step 1: Rewinding Brushless Motors WYE or Delta

For this tutorial, I will be using Dynam E-Razor 450 Brushless Motor 60P-DYM-0011 (2750Kv). It is a Delta wound 8T (It means 8 turns) quad wind. The winding pattern described in this tutorial (called an ABC wind - ABCABCABC as you go around the stator) works for any brushless motor with 9 stator teeth and 6 magnets.

Step 2: Knowing Our Motor

First, obviously you'll need to remove the old wires from the motor. Be sure to count the number of turns around the armatures as this will give you an idea of how to rewind the motor. The direction is not particularly important at this point.

You will also want to note whether it is Delta or Wye terminated. A Wye terminated motor will have three wires going to a central point called the neutral, which is not connected directly to a motor lead. A delta has no such connection, just three motor wires. Often the neutral point one WYE has a piece of heat shrink over it to keep it from shorting to the stator. Our motor is Delta Connected.

Step 3: Starting the Rebuild

Before you do anything, I highly recommend insulating the stator. Take it from the king of stator shorts, a stator short can easily destroy your speed control. I cannot stress enough how much easier your rewind will be if you do this.

Most stators will be already insulated, but if you cooked your motor as well as I do that coating is toast, in which case you'll need to reinsulate it. Start by using a small hobby file to smooth all the rough corners on your stator. I used Black Rubber Paint.

Step 4: Insulating Stator

1. Deep the stator in black paint and take off.

2. Wait till paint set off.

3. This is procedure is optional.

4. If you burned the motor then it's mandatory.

5. If you want to change motor specification or your motor didn’t cook then it is optional

Step 5: Rewinding

1. Ok, now to rewind. First, you must choose the number of turns you want. My motor was 8 turns, and I liked it, so I'm going to rewind it with 8 as well.

2. Here 8 Turns means, 8 strands of enamel coted copper wire are connected in parallel which is wound on stator pole 8 times.

3. Here 36 AWG copper wire is used.

4. Rule of Thumb - fewer turns is a hotter motor and will yield a higher kV and current draw. Go too low on this, however, and the motor may not run as the speed control may not detect the motor's position. You'll also have to choose whether you want a Delta or WYE termination.

5. We are using delta connection as it was factory default.

Step 6: Getting Winding Pattern

Now you need the winding pattern. This motor is a 9N6P (9 stator pole, 6 magnet ). Therefore the winding pattern is ABCABCABC (each wire is wound every third tooth). This winding pattern will not work with the very common 12N14P motor.

So before you start winding, count your magnets and stator poles and determine the winding pattern from the list below. Lower case letters indicate winding that tooth in the reverse direction.

Common stator pole/magnet pole configurations:

N denotes number of stator "wire wound" poles, P denotes number of rotor "permanent magnet" poles.

9N, 6P - Common for helicopter motor, EDFs, and other high speed applications. The winding pattern is ABCABCABC

9N,12P - very common to many small outrunners. This is also the most common CD-ROM motor configuration. Winding Pattern is ABCABCABC

12N, 14P - Common for higher torque applications. Noted commonly for its smooth and quiet operation. Winding Pattern is AabBCcaABbcC (lowercase implies reverse in winding direction) OR AaACBbBACcCB (I find this winding easier)

Other configurations:
9N, 8P - Magnetically imbalanced motor configuration occasionally found in high speed applications. This configuration is best terminated as WYE to minimize vibration. (very rare) - AaABbBCcC

9N, 10P - Highly magnetically imbalanced motor that often makes for noisy running. This configuration is usually only built by do it yourself motor builders. This motor is best terminated WYE. Winding pattern is AaABbBCcC

12N, 16P - A not so common but still used style. It has been overshadowed by the 12N, 14P. Winding pattern is ABCABCABCABC

12N, 10P - Higher speed variant of the DLRK motor. Occasionally found in helicopter motors. Winding Pattern is AabBCcaABbcC (lowercase implies reverse in winding direction).

12N, 8P - Even higher speed than the 12N, 10P. Winding pattern is ABCABCABCABC

Step 7: Winding Design

As we are planning on terminating Wye, mark the ending terminal of the wire. We'll need to join the ending terminals of all three phases when it comes time to terminate the motor as shown in following.

Step 8: Start Winding

1. Now you can start winding.

2. I used New-b wire (36 AVG) from a nearby winding shop.

3. It has extra insulation to prevent shorts. I chose three strands of 36 gauge wire. So it will be an 8 turn of 8 wire bundle wind.

4. Start winding with any pole you like. Go only in one direction (I went clockwise). Once you complete the number of turns you decided on earlier, skip two poles and continue winding the next. Repeat this process until one third of the poles are wired. It should look like the picture below when you are done.

5. Here third winding is to be done.

6. Now before you begin with your next set of armatures, check for stator shorts with an ohm meter (multi tester). The resistance between the wire and the metal of the stator should be infinite (i.e. not continuity).

7. If you don't get a short, good job. Move on to the next set of armatures. If you have a short, unwind that entire phase get a new wire and start over.

8. Side note: When winding, do not tug on the wires too hard. 1-2 lbs is plenty. Winding too tight will result in a shorted winding to the stator. If you find that your wires are not snug against your stator you can use a non-metallic object such as a broken prop, flat carbon rod, or my favourite, a credit card to slide between the stator poles.

9. Do tag the start and end of winding.

10. Here start tag is S1 and end of 1st winding is E1 as seen in picture.

Step 9: Ready for Another Set?

1. Ready for another set? Start with a new wire on any other pole and repeat the above process. Make sure to test for shorts after each phase.

2. You'll notice the stator becomes crowded very quickly. You can clear some room with a dull object such as a credit card.

3. Don’t forget to tag other winding start and end points.

Step 10: Connecting Windings

1. Now we have 6 wire ends tagged S1,E1,S2,E2,S3,and E3.

2. Connect E3 S1, E1 S2 and E2 S3.

3. Now we have 3 end which are motor terminals A,B,C

Step 11: Wire Insulation & Bullet Connector

1. Add wire insulation to copper wire. Here I used insulation sleeve of Multicore wire to insulate them as shown in a picture.

2. Add bullet connector to motor terminals as shown in a picture.

3. Add heat shrink tube coating for extra strength and insulation.

4. Done our motor is ready.