User’s Manual for Advanced Axial Flux Synchronous Motors and Generators
www.emrax.com Version 4.5 / January 2017 52
The cables should be as short as possible. For longer cables the diameter of the cable must be bigger. Power
cables must be shielded and distant enough from the communication cables.
4. Setting the controller software:
Basic controller software settings must be set in the controller software. Basic controller settings are published
on our web site: link. These files are for the Unitek controller. Other controllers use similar parameters, which
can be set by using these parameters and the Technical Data Table of the motor.
Afterwards auto-tuning must be made. This means automatic adjustment of electrical angle according to the
mechanical rotor position. This is a very important step for proper operation of the engine! When auto-tuning
starts the motor slowly rotates for 360 mechanical degrees. Every controller has different system for automatic
adjustment of electrical angle, so make sure you read the manual of the controller or consult with the
controller producer. Here is a video, which shows auto-tuning EMRAX motor with Unitek controller:
https://youtu.be/yuyPS_RCWQ8
Now you can start the motor and adjust software parameters according to your application. Be sure you enter
the parameters that are in accordance with the Technical Data Table! Otherwise it causes a void of warranty.
20. How to choose the correct EMRAX motor type for every application:
1. First you need to know what RPM and torque you will need for your application. You have to make sure, that
the desired RPM and torque (without transmission gear) do not exceed maximal RPM and torque listed in
the Technical Data Table for the specific EMRAX motor. You also need to make sure, to consider the
Torque/RPM graph! The torque also depends on the controller current of the motor, therefore the controller
needs to have enough high phase current to get enough high torque.
2. In the Technical Data Table you can find Specific load speed (RPM/1Vdc). With this data you can calculate
how many RPM you will get at desired battery voltage (Vdc) at load application.
*It is possible to achieve higher RPM with magnetic field weakening (MFW). You can use magnetic field
weakening when torque is at maximal value. At magnetic field weakening the torque slightly decreases, but
the RPM rises and consequently the power stays the same (take a look at the equation below). Magnetic
field weakening can be set in the controller software. EMRAX motors have 10 pole pairs, therefore it is
recommended to weaken the magnetic field for 15-20% to achieve the best performances. With higher % of
magnetic field weakening the motor can run faster with very good efficiency, which drops only for 1, 5% at
80% MFW. We recommend MFW only for a short time (few min in case full motor power), because of a very
high phase current between the motor and the controller.
3. Now you can calculate the power, using this equation:
At a lower RPM (motor rotation), you can expect lower motor power at the same torque. At a higher motor
speed you can expect higher motor power at the same torque.
Mt……torque [Nm]
P………power [kW]
n………motor rotation [RPM]
In case you need higher power we recommend you to increase battery voltage (Vdc) instead of increasing
motor current – because cables with bigger diameter are needed and consequently the weight is bigger. It is
better to use a High Voltage motor if you need higher speed (RPM).
4. Example for 228 MV:
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