Selecting Electric Power Setups John Hoddinott, 21

Transcript:Selecting Electric Power Setups John Hoddinott, 21:
Selecting Electric Power Setups John Hoddinott, 21 May 2015 Components of the Setup Brushless Motor Electronic Speed Controller (ESC) Battery (Usually LiPo, but could be NiCad, NiMH, LiFe, etc) Propeller Connectors/Wiring Why Brushless Motors? Brushless motors offer several advantages over brushed DC motors (according to Wikipedia!): high torque to weight ratio increased efficiency increased reliability reduced noise longer lifetime (no brush and commutator wear) reduction of electromagnetic interference Size Matters! Why is the Setup Important? Performance Efficiency (longer flight times/smaller & cheaper batteries) Safety Getting it Wrong! Some Definitions V - Voltage (Potential Difference) in Volts (V) I - Current in Amperes (A) P - Power in Watts (W) P = V x I (Ohm’s Law) RPM - Rotations per Minute kV - RPM per Volt mAh - milliamp hours (a measure of battery capacity) C rating - A measure of the discharge (or charge) rate of a battery as a multiple of its capacity My Process Estimate Power Needed Decide on Maximum Flying Speed Calculate Ideal Thrust Calculate (or Measure) Maximum Propeller Diameter Select Preferred Battery Voltage Find a Setup Test/Check the Setup Step 1 - Estimate Power Step 2 - Flying Speed Step 3 - Thrust How much thrust do we need to fly? Less than you might think! Step 3 - Thrust to Weight Examples Step 4 - Propeller Diameter Bigger is better (usually) Step 5 - Battery Voltage Use Ohm’s Law to calculate the battery voltage that provides the desired power with sensible current level. P = V x I Therefore V = P / I But what is a sensible current level? Step 5 – Battery Current Capacity Battery current capacity is calculated by multiplying the pack capacity (in mAh) by the C rating. Example – a 2200 mAh pack rated to 25C can produce: 2200 x 25 = 55,000mA = 55A Step 5 - Connector Current Capacity Deans - 100A XT Series - 30/60/90A EC3 - 60A EC5 - 120A JST - 3A Step 6 - The Setup Using the data we now have (power, flying speed, thrust, propeller diameter and voltage) we now have all the information to find a setup that works. But how? Get on the internet and search! Step 6 - Typical Motor Specs Step 6 - Some Good Web Sources AXI Motors http://www.modelmotors.cz/index.php?page=1 Hacker http://www.hacker-motor-shop.com/?shop=hacker Scorpion Power Systems http://www.scorpionsystem.com Eflite http://www.e-fliterc.com Emax http://www.emaxmodel.com Example Setup for Seagull E-Pioneer Example