Support Center - FAQ - Motors

How do I change which way the motor spins (rotation direction)?

To change a motors direction, swap any two motor leads.

How often should bearings and shafts be replaced on KDE Direct UAS Brushless Motors?

There are many outside factors that can impact the operating life span of motors. These include environmental effects such as sandy or dusty conditions, hot summer temperatures, and corrosive elements such as salt water. In most applications, the lifespan of the motor is determined by the bearing manufacturer’s rated lifespan. Our designs use certified NMB and NSK branded bearings with a nominal lifespan of 100-200 hours. Differing conditions can either increase or decrease this lifespan, and we encourage regularly inspecting the motors for any signs of bearing failure that could lead to decreased performance and even failure from seized bearings. With the proper maintenance, all of our devices can last for many years with Bearing and Shaft Replacement Kits for the Multi-Rotors and Replacement Kits for the Single-Rotors for sale.

Does motor maintenance require sending products in to KDE Direct, or can it be done anywhere?

All KDE Direct UAS Brushless Motors are designed for customer servicing with a detailed instructional video provided in the Technical Videos section of the Support Center. Direct Video Link (YouTube). Please review the video for step-by-step instructions on how to replace bearings and shafts (full disassembly/reassembly). Bearing and Shaft Replacement Kits are available for purchase.

Do you have replacement bullet connectors for motor leads?

Replacement bullet connectors can be found here.

What motor edition is ideal for the DJI™ Phantom® 2 Series?

Use four (4) of the KDE2315XF-965 Brushless Motors and Adapters for optimal performance with the standard battery system (3S voltage) and are directly-compatible with the stock ESCs for drop-in operation. Please feel free to review the Installation Instructions for additional details.

What motor edition is ideal for the DJI™ Phantom® 3 Series?

Use four (4) of the KDE2315XF-885 Brushless Motors and Adapters for optimal performance with the standard battery system (4S voltage) and are directly-compatible with the stock ESCs for drop-in operation. Please feel free to review the Installation Instructions for additional details.

I am running tests on your motors and the results are different from your published data. What accounts for the discrepancies?

There are always discrepancies in Dyno testing from either in-flight tests or static bench tests. The testing conditions (altitude, temperature, and humidity) can significantly affect the tested data. Our testing conditions are reported for the day of testing, and the full specifications of our Dynamometer test site can be found here. Running with an alternate-brand ESC will also lower-performance since it has not been optimally tuned.

What settings will make the motors produce the same output?

There is always a slight difference between motors’ responses. This is due to the manufacturing tolerances of the internal components (ICs) of the ESCs and the motors. These differences are mitigated through a flight controller with independent mixing that will balance out the individual ESC and motor responses for a stable flight. Updating all ESCs to the latest firmware and selecting identical settings will also mitigate these differences.

What is included under a motor’s specified weight?

The weight of KDE brushless motors includes two numbers. The first number is the weight of just the motor. The second stated weight is the weight of the motor, the exit leads, bullet connectors, and shrink-wrap. The weight of the motor will decrease as the wires are shortened (as done for various custom-installations) and bullets removed for direct-soldering to an ESC. Any additional weight such as propellers or adapters must be factored in based on the components in question.

What is the mean time between failures (MTBF) for KDE Direct brushless motors?

There is no standard MTBF for UAS equipment as the environmental operating conditions are the driving factor in components’ lifespan. Proper care and maintenance of the equipment can extend its lifespan and performance.

What is the peak current burst of KDE brushless motors?

The peak current limitations of the motors are no longer stated in the motor specifications. This is due to the external contributing factors that can change the peak-current capability of the motors outside of the nominal design (such as air temperature, diving ESC, load conditions, etc.). The typical peak-current (5 second) capability of the motors for safe-operations can be calculated as 117.5% of the continuous current rating. Example: If a motor’s current rating is 100 Amps, the peak can be 117.5 Amps. We do not guarantee or warranty motors pushed beyond the motor’s specified limits. These uses are considered out of normal operation and can damage the motors.

Are KDE brushless motors waterproof?

KDE Direct motors are electrically insulated guaranteeing operation in all adverse weather and environmental conditions. If the motors are continuously operating in fully saturated conditions, increased maintenance and inspection of the motor bearings is required. We have an Instructional video that displays the capability of the KDE Direct UAS Brushless Motor series in water and the recommended maintenance.

What is the temperature rating of KDE Direct UAS Brushless Motors?

The entire motor is rated to over 400°F (windings rated to 240°C and magnets to 180°C), so there are no concerns of any damage from heat-generation. In actuality, when the motor is running in the flight the centrifugal fan is efficient at keeping the motor cool and consistent, designed to run around 120°F-140°F during a flight for optimal performance. When you land and shut down the centrifugal fan you’ll experience a motor that feels much hotter than during operation, simply due to the high-performance design of the motor. With high-performance motors, there is a high-copper concentration stored in the motor which naturally stores heat during flight. When the fan is shutdown all the heat is expelled to the outer case and what you are feeling is the heat conducting to the Aluminum Fan, as it’s designed to do. In this, the temperature may feel hot but this is normal for all high-performance motors and nothing of concern due to the quality of the components.

How do various factors: propeller size, drive frequency, advanced timing, synchronous rectification and acceleration rate affect the temperature/ performance of KDE brushless motors?

Propeller size:
If larger than recommended propellers are used on a motor it can result in high temperatures due to the stress on the electromagnetic core operating outside of the optimal torque-curve.

Drive Frequency:
When running the drive frequency at PRECISION (30 kHz – 32 kHz), the motor will run smoother and have faster rates of regenerative-braking, but the temperature is typically close between the three settings to the coils of the motor. The drive-frequency does not influence motor temperature to a significant degree.

Advanced Timing:
DYNAMIC advanced timing will reduce motor temperatures, as the lower-timing is more efficient overall for the propulsion system. The drawback of using a lower-timing is the potential maximum thrust will be lessened (~5%) in comparison to running the PRECISION advance timing mode.

Synchronous Rectification:
The activation of Synchronous Rectification will raise motor temperatures (in most cases), as now the motor is being driven in both acceleration and deceleration phases (aka, generation). In this regard, there are no periods of time when the coils are not energized, so the temperatures are typically higher in the brushless motor when engaged. That being said, S.R. significantly reduces ESC operation temperatures and increases the overall system efficiency due to recycling active-freewheeling currents, so the overall propulsion system benefits with this technology.

Acceleration Rate:
The ACCELERATION RATE can significantly influence temperatures. Reducing the speed will reduce the peak acceleration rates (and peak currents to the motor), similar to the throttle on a car engine. Push this to ULTRA-HIGH, and the motor will be asked for faster and harder peak acceleration/deceleration rates. Lower this to MEDIUM, and the load requirements on the motor are lessened, helping maintain cooler operating temperatures on the motor.

Are the KDE Direct COAX motors available for purchase?

KDE Direct is continually leading the industry in new technologies and innovations. The coaxial-motor is one such product brought to the world in 2016. These motors are custom-designed for various heavy-lift and commercial applications and can be produced for your specific requirements (such as for the Shotover U1 system). Please review the Custom Products and Design Inquiries webpage for additional information on KDE Direct’s capabilities for your production needs.

How can I order KDE Coaxial brushless motors?

The COAX motors are developed specifically for each client, as the central core has a mounting-profile custom for each airframe. Production terms and minimum order quantities (100pcs) apply to COAX motors. Please contact our sales team today for a project estimate.

Is there any loss of thrust from motors in a coaxial/dual configuration?

For two motors working in a dual-configuration (COAX), there is a loss of thrust-generation on the lower-COAX portion, due to the pre-accelerated air of the upper-COAX mechanics. This results in a loss of ~8%-14%, depending on the system and spacing between the motors.

Anything to expect from the motor on the first flight?

The UAS Brushless Motors are near maintenance-free (triple-bearing supported) and won't require anything when first received - simply bolt in the motor and it's ready for operation. The motors have a specialized varnish applied to the windings to prevent any shorts or shifting when the motor is energized (more expensive manufacturing, but high-quality) and as such, may produce a minor electrical smell during the first few flights when brand new. This is in similar fashion to buying a new car where the engine compartment will produce varnish vapors during the first 1,000 miles of driving. Once the motor has been flown for a few dozen flights the varnish vapors will disappear.

Is it normal for a brand new motor to make a scratching noise when you spin it by hand?

A new motor that is not running smoothly is typically caused by a minor-amount of balancing epoxy that has expanded (during production the CNC machine places the dynamic balancing epoxy for smooth operation to the magnet bell assembly) and may be touching the stator during rotation. This is easily fixed by running the motor for a few minutes at full-throttle which will break-in the motors and seat the bearings. It is rare to have any bearing issues out of production, so the typical reason for any sound/rattling is from the initial break-in period of the motors.

One of my motors died in mid flight, what happened?

The typical reason for an in-flight shutdown is an electrical disturbance, such as a disconnection between the PDB and the ESC or via one of the ESC motor leads to the Brushless Motor. Check through all electrical connections and any exposed surfaces and make sure these are appropriately covered via heat shrink-wrap to prevent any chance of electrical conduction to the airframe. Also, check the control line from the flight-controller to the ESC – many times these are ran over sharp areas of the airframe. Any small cut or pierce through the silicon-wire protection can cause a shutdown from the electrical-disturbance of the control-line to the ESC.

What is the high pitch noise I hear coming from my KDE motors when they are set to 'Dynamic' Drive Frequency? If I change the settings to 'Precision" will it go away?

The electrical noise from the motor is commutation noise, as the DYNAMIC drive-frequency runs in the audible range of 16kHz – 18kHz. Precision mode will remove this audible noise (commutation from 30kHz – 32kHz is outside our auditory range) but the ESC will also operate hotter due to the increased switching frequency.

I am looking for a propulsion system that will fit specific design requirements. How can I determine what KDE Products to use?

Please use our online system configurator
By entering in your specific parameters, it can help you determine the best KDE propulsion system to fit your project's needs.

My motor started to slowly beep when connected to a power source. What does that mean?

The continual beeping is a warning-signal that no throttle command is being received. It will continue to remain in this safe-protection mode until the arming tone is received from the receiver or flight controller. The KDE Direct UAS ESCs are OPTO-isolated and require power along the red-wire of the control lead (most receivers and flight-controllers support this)

Can motors from the Single Rotor Brushless Motor Series be used in a multi-rotor UAS?

The Single-Rotor Brushless Motor Series have been used in multi-rotor UAS applications where the propeller is directly installed to the shaft of the motor rather than direct-attachment to the magnet-bell assembly. The Single-Rotor Motors are designed for high-RPM so they are generally used in applications with a transmission drive, such as a belt-drive from the motor pulley to the propeller to generate the high-torque optimal for the multi-rotor applications. The Single-Rotor motors are generally more suitable for fixed-wing and airplane applications (in either the push or pull-configuration) where the high-RPM is beneficial for the propulsion.
The UAS Multi-Rotor Brushless Motor Series is optimal for multi-rotor applications where the propeller is attached as a direct-drive component to the motor so the electromagnetic layout is optimized for this application. In these types of applications, fast acceleration and deceleration rates are required for flight-stability and dependability so the motor construction is unique to the requirements. For multi-rotor type applications, these are the motors used in 99.9% of the systems. Only for very specific applications (where a transmission drive or other custom-aspect is used) are the single-rotor type motors used.

How do I calculate motor torque?

With BLDC motors, the torque constant relationship is linear. Each motor lists the torque constant under the specification tab on each motor's product page. Since the torque constant is based on the DC coming in and the torque output coming out, you can calculate torque with the following equation:
Torque constant (Nm/A) * DC current (A) = Torque (Nm)

What grade magnets does the motor use?

Curved N45UH Neodymium sintered-magnets are used.

Are the motors delta or wye wound?

All motors sold online are delta wound but different winding options are available for custom motors.

How are the motor constants calculated?

Rm is the motor's resistance between two motor phases (KDE motors use delta winding)
Kv changes based on number of turns per coil and wire gauge
Ke = 1/Kv
Kt = 60/(2pi*Kv)
Km = Kt/sqrt(Rm)
Io@10v is the motor's idle current (no-load current) at 10V