Drive Calc (D-Calc) is available for Windows, Mac and Linux. The equivalent inertia of an adjustable speed drive indicates the energy required to keep the system running. Horsepower is work done per unit of time. The torque required to accelerate a body is equal to the WK2 of the body, times the change in RPM, divided by 308 times the interval (in seconds) in which this acceleration takes place: The constant (308) is derived by transferring linear motion to angular motion, and considering acceleration due to gravity. The ammeter and DVM (digital volt meter) can be cheap multimeters, as long as the one used for amps can measure current to at least 5A. The solid horizontal lines in Figure A represent the boundaries of strips; the lengths of the broken lines the average accelerating torques for the selected speed intervals. Hobby King sells a product called the "K1 KV/RPM Meter" which was designed to measure the Kv of brushless motors. Apply our formula 1, Distributed freely and customized for a variety of commercial hobby motors, e.g. Scorpion Motors (Scorpion_Calc) & HiMax Motors (HiMax Calculator). 3. when O.S. If a variable power supply is not available, try battery packs of different voltages till you find one that gives the closest speed to what is required. Therefore, a manufacturer may round the Kv value to the nearest 50 or 100 according to what they measured on a test sample. 2. Single & Three Phase Line kVA calculator is an online tool used in electrical engineering to measure the unknown quantity by two known quantities applied to the below formulas for single phase and three phase connection. More accurate modeling of Io is possible by employing advanced curve fitting equations, but then multiple readings at various voltages and speeds will be required. 2. Equipment needed: Ammeter, voltmeter, 10-20 Ohm (10 Watt) resistor and a high capacity battery of about 12volt. Orders with notes such as these can not be processed for two reasons. The answer is "yes", and it is actually quite easy to do at home with relatively inexpensive equipment that you may already have. The list is not all-inclusive. Each strip corresponds to a speed increment which takes place within a definite time interval. Thus, we need to determine the "equivalent inertia" of each moving part at a particular speed of the prime mover. If, for example, we have simply a prime mover and a load with no speed adjustment: If we want to accelerate this load to 1800 RPM in 1 minute, enough information is available to find the amount of torque necessary to accelerate the load. Sales Orders are often entered with a note under special features such as: -----"Suitable for 10 starts per hour"Or----"Suitable for 3 reverses per minute"Or-----"Motor to be capable of accelerating 350 lb.ft.2"Or-----"Suitable for 5 starts and stops per hour". Adequate thermal capacity would be required in slip couplings, clutches or motors to accelerate or plug-stop these drives or to withstand stalls. Duty cycle refers to the detailed description of a work cycle that repeats in a specific time period. Electric Power Formulas & Equations in DC and AC 1-Φ & 3-Φ Circuits. Both are very realistic and powerful stand-alone applications that are free to download and use. Now that we know how to measure the three important motor constants, Kv, When the speed-torque curves for the motor and blower intersect there is no torque available for acceleration. Figure A shows the speed-torque curves of a squirrel-cage induction motor and a blower which it drives. 3. Efficiency = Power Out / Power In Apply the formula to get the Kv of the motor alone - without the effects that ESC settings will introduce. speed, and not by varying the speed with the ESC. In other words, with a certain size or pitch propeller, a motor will have a certain efficiency at WOT. Km = Kt /. Rm (or Ri) is the resistance of one phase of a motor (after termination). On commercial motors, the stated Kv is usually a nominal value, because no two electric motors are completely identical. Being an electric model flyer, I already had an accurate ammeter in the form of a Hyperion e-Meter. The motor then drives the blower at constant speed and just delivers the torque required by the load. Because of the complexity of the Duty Cycle Calculations and the extensive engineering data per specific motor design and rating required for the calculations, it is necessary for customer to refer to an electrical engineer for motor sizing with a duty cycle application. CLICK TO CLOSE WINDOW. It is a strong argument for measuring your own motor constants. Note that TAcc is an average value of accelerating torque during the speed change under consideration. For estimating, pump efficiency may be assumed at 0.70. In order to calculate efficiency, we have to run the motor with a load (propeller) attached while taking Volt and Amp measurements using a reliable Watt meter. Apart from supporting the respective branded motors, any electric motor (even custom-wound) can be simulated. I strongly suspect that this meter uses the "Drill Press" formula described previously. Obtaining this information and checking with the product group before the order is entered can save much time, expense and correspondence. In the example, the result can be obtained as follows: The total WK2 equivalent is that WK2 seen by the prime mover at its speed. 1. This equation becomes a common denominator on which other calculations can be based. 2. I suggest measuring the speed of the drill press beforehand. One possibility is that the efficiency of the motor, as well as the efficiency of the complete system (motor, ESC and battery) can be calculated. All that is required is a way to measure volts accurately (multimeter), a tacho to measure RPM and a drill press or another method to spin the motor at a constant speed. Efficiency changes as the load on the motor varies. For brushed motors, this is straightforward: Kv = RPM / Volts. If the voltage goes up (by adding a cell or two), the efficiency will also change. In order to find the total time required to accelerate the motor and blower, the area between the motor speed-torque curve and the blower speed-torque curve is divided into strips, the ends of which approximate straight lines. This is equal to the WK2 of the prime mover, plus the WK2 of the reducer times (1/3)2, plus the WK2 of the load times (1/3)2. The three motor constants which are very handy to know about any electric motor are: 1. Then a tachometer set to 2-blade setting can be used to measure RPM. Io It's best to use a variable power supply and varying the RPM by adjusting the voltage until the desired operating RPM is reached with the ESC at max. Power Out = Power In − All Losses For a detailed explanation of each formula, Click on the links below to go right to it. If a different size or pitch propeller is used, the efficiency will change. This is a new pop-up window on top of your GeneratorJoe browser window. Another important feature is that it works from minimal data input, since no real-world data is required, except when simulating custom motors. Obviously, the more accurately the constants are measured, the. Measure the AC Volts (RMS) with a multimeter. Synchronous Speed, Frequency And Number Of Poles Of AC Motors, Relation Between Horsepower, Torque, And Speed, Locked Rotor Current (IL) From Nameplate Data, Effect Of Line Voltage On Locked Rotor Current (IL) (Approx. Kt = 1/Kv (SI units: with RPM in rad/sec) Some manufacturers give a 'Maximum Efficiency' rating, but don't be fooled. the 'four constant model' which is outside the scope of this article.

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