Mounting & Cooling
This page provides mounting instructions and thermal management guidelines for the AJAX electronic speed controller.
Capacitor​
AJAX comes with an onboard solid capacitor that provides sufficient filtering for most use cases.
Additional Bulk Capacitor​
For applications involving repeated rapid throttle changes, SIGSA recommends adding an external bulk capacitor across the power input pads to provide additional voltage ripple filtering.
A bulk capacitor with low ESR and high ripple current rating helps minimize heat generation under dynamic load conditions.
The following capacitor is recommended by SIGSA:
| Specification | Rubycon ZLH Series |
|---|---|
| Part Number | 50ZLH820MEFC12.5X35 |
| Capacitance | 820 µF |
| Voltage Rating | 50 V |
| Type | Electrolytic (Low ESR, High Ripple Current) |
Mounting​
The AJAX features a standard 30.5 mm × 30.5 mm (4-point) mounting pattern compatible with most 30.5 mm drone frames. Electrically-isolated silicone rubber spacers rated for M3 fasteners are included with each unit.
Never install the ESC without the supplied silicone rubber spacers. Direct metal-to-board contact between screw studs and the PCB can result in short circuits, leading to irreversible ESC failure and potential fire hazards. Damage caused by improper mounting without the spacers may void the warranty.
Electrical Isolation​
Maintain a minimum 0.6 mm air gap between exposed contacts and any conductive materials in the mounting assembly. All thermal interface materials must be electrically insulative to prevent short circuits.
Environmental Protection​
The AJAX is a bare board with numerous exposed connections. Contact with water, heavy moisture or significant amounts of dust/particulate can result in unit failure.
Ensure appropriate environmental protection is implemented based on your aircraft's operating conditions:
- Use conformal coating or heat shrink tube for moisture protection
- Consider enclosures for dusty environments
- Ensure adequate ventilation for cooling airflow
Thermal Management​
The AJAX's compact size and high power density require effective cooling to maintain components within safe operating temperatures.
Orange highlights indicate high heat generation areas.
Cooling Recommendations​
The AJAX has a particularly high power density, making effective cooling essential. To ensure continuous operation at rated phase current, your cooling solution must effectively dissipate heat from the unit to ambient. The recommended temperature limit for long term reliability is 75℃.
- Passive Cooling: Mount to a metal heatsink or aircraft frame with adequate thermal mass. SIGSA recommends placing a heatsink on top of the MOSFET packages for optimal heat dissipation.
- Active Cooling: For high-current applications, ensure direct airflow over the ESC.
- Thermal Interface Material: Use high-quality thermal pads or paste between the ESC and heatsink.
Monitor ESC temperature during initial testing to ensure your cooling solution is adequate for your specific application.