Esc / electronic speed controller


If you are searching an esc to participate in drag racing you have to be aware of the spec `s of an esc.

You should look for a combination of features that all help contribute to the good performance of the drag racer.

We will deal with the following properties:

1. Maximum output in amperes
2. Voltage
3. Switching Speed
4. Cooling
5. Bec / opto
6. Thermal overload
7. Programmability (Reverse / Brake, voltage cutoff, timing / direction)



Maximum amps esc


Now how much amps your rc motor is drawingFirst, the esc you will use has to fit the engine. If you are going to use a motor that draws 80 amperes for example, the controller needs to easily handle that. The basic capacity that the ESC should be able to deliver must be more than the motor uses up according to the supplier / manufacturer. That way you will one hand avoid the that you burn the esc in no time and on the other hand get lousy performance because the esc can`t deliver enough power to your engine at full throttle. The "burst" which ESC can deliver is also important. After all, that's really the only thing we are going to use during a drag race. Make sure you`re esc can clearly deliver more amp`s then the engine needs (specified by manufacturers spec`s) and observe the burst that it can deliver. The maximum use specified by engine manufacturers is an average wich will be exceded. Remember in drag racing the max. is the standard.



Voltage of an esc


Simply put, there is just as much volt`s coming out of you`re esc as you put into it. Connect a 3s lipo battery that delivers 11.1volt (3x 3.7 volts per cell) and the engine will also be fitted with 11.1volt. What the esc does is shoot pulses. The more gas you give the faster the pulses come. Because 11.1 volts is the maximum that may be used in a rc dragster that meets the official contest rules, it makes no sense to buy an esc that can take up 35volt. Only in the "extreme" class you may use more than 12.8 volts. In this class you will not encounter many opponents.



Switching Speed of an esc


Every electronic speed controller has chips which have a maximum switching speed. If you pay attention you will encounter switching speeds of 50,000 per minute to as much as 200,000 times per minute. The specified switching speed indicates how many pulses per minute an esc can shoot to the motor. Because most motors, for mechanical reasons can`t handle more than 50,000 to 60,000 revolutions per minute this is usually more than enough. Because an esc has no idea what motor it controls, the pulses for the switching speed will not adapt to the amount of poles the motor has. A standard brushless motor is equiped with 2 poles. When you use a multipolar motor, the switching speed is divided by the amount of poles. An 8-pole motor will therfore get less pulses per polar per minute. A high pole motor connected to a controller that "only" gives 50,000 pulses per minute will therefore not give you ideal performance. In some cases, it may even break down a controller when connected to a "to many" pole motor.



Cooling


Burning esc, speedcontrollerControllers have to work hard and get hot. Very hot. Even so hot that they can burn. For this reason, most of the "High performance" controllers are cooled. The cooling system may exist of a cooling flanges usually of aluminum, a fan, or a combination of both. Now take in mind that a drag race is very short, so the esc will not heat up of 1 single race, but cooling may still be important. The secret is in the cause of the heat. The heat is loss of power. The mosfett `s in the controller will produce heat and unfortunately less accurate performance when they are hot. It is therefore important to keep things, even in the short time that the race takes, cool. With a continuously running fan you can, even on a hot summer day, cool you`re esc to a point that is is cooler than the outside air before the start of a race.



BEC / Opto


When buying, take in account BEC or Opto. It indicates whether you can uses the controller to get power to your servos and receiver. A controller with BEC has this capability. Behind the notice BEC it will say what voltage it runs through the BEC and how many amps it can handle. The voltage is important for the proper operation of your receiver and servos. The amperage is less important in a drag racer because you already want to bring as little equipment as possible. Never buy a Opto controller for a drag racer. It would mean that you need to bring 4 (heavy) extra AA batteries power to your servos and receiver*.

*A workaround for the lack of a BEC on the ESC is an UBEC. It can be connected directly to the battery and reduces the battery voltage to 3-5 volts. This lower voltage can be used to provide receiver and servos of the correct volts. This way, no extra batteries have to be placed for the servo and receiver. The controller itself is just directly connected to the battery.



Thermal overload protection


Is just a protection against overheating. Very convenient but we have just agreed we only use a very well cooled esc. If you`re still not sure then thermal overload protection nice to have but in our opinion unnecessary.



Programmability


programeerbaarheid van een snelheidsregeklaarThe more you can program in your esc the better. It is generally done by a programming card. A program card connects to the signal cable from your esc. The ESC must be connected to the power supply. It varies by controller and programmingcard what exactly can be set.


The "Must Heaves" include the following matters:

1. Voltage cutoff
2. Engine Timing (sometimes referred to as soft and hard)
3. Break and break power



Voltage cutoff


Voltage Cutoff determines when the controller shuts down power. This can be set to a voltage that matches the lipo battery that `s to be used. Sometimes what you want to test drive on 2 cells (7.2 volts) or just want to try the maximum to 3 cells (11.1 volts). If you’re not able to change the cutoff settings you’re 3s lipo will decease very quickly or your 2s lipo `s won’t give sufficient voltage. In drag racing you can unfortunately, not always be careful with the load of your battery pack. It is of course important to keep battery `s, maximum power consumption of the controller and maximum demand of the engine in alignment, but sometimes you will find that the maximum result is achieved only when everything is right on the edge. At that time you will have to set the power cutoff down 0.1 volts per cell to avoid power cutoff halfway through the race because the esc notices you’re short 0.1 volt on 1 cell. Read more about this in lipo pack `s.



Engine Timing


With timing you can adjust the moment of the pulse relative to the position of the magnets (poles). It varies by engine what timing is ideal. Due to the tremendous speed at which the magnetic field must be created by the pulse it can occur it`s just not given at the exact right moment. If the pulse is too late, the magnet is already partially past the coil when the maximum magnetism is generated. This is a loss. Apart from the loss which occurs when the time is not ideal, there is also a clouding of the magnetic field at the time the transition takes place to the next pole. Correct adjustment of the timing is a matter of trial and testing.

Finally, some controllers can change the rotatin direction of the motor. This is especially useful when wires between motor and esc are not easy exchanged. In the cases where wires can be easily interchanged, it is sufficient to turn around 2 threads of the motor in other change the direction.


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