# Calculating Power Consumption of Electric Linear Actuators David Eidelshtein
PA Engineer

Power. Wattage. Energy Consumption. All these terms can be used when discussing electric actuator power consumption.

Electric linear actuators that are manufactured by Progressive Automations use DC motors. Depending on the force that the actuator can apply, the size of the DC motor will vary. The higher the force, the larger the DC motor.

DC motors with a low current draw will typically be used in the actuator with a lower force rating – same goes for a DC motor with a higher current draw for actuators with higher force ratings.

Current draw ratings are provided as a threshold for the maximum current that the DC motor will draw when applying a force equal to the rated force of an actuator.

For example, an in-stock PA-04-400LB model has a 400lbf load and 12A current draw rating. In this case, when 400lbf is applied to the actuator, the current draw will be 12A with a 12VDC input. Although 12A at 400lbs is the rated value, the use case of the actuator in your application may result in a lower force being applied.

### Data Interpolation

Let’s run a scenario where a force of 150lbf is applied onto the PA-04-400LB model.

Below is a load vs. current graph. We will need to create an equation to interpolate the current draw at a specified force rating. The no-load current is 4A and the full-load current is 12A. What we see is a direct linear relationship between an increase in load an increase in current draw. Since this is a linear relationship, we can apply the formula:

y = mx + b

Where,

y = Current (A) @ 12VDC

m = Slope of the 400LB PA-04 current vs load line

b = No-load current draw of the PA-04

Since we have all the values for y, b, we need to determine m

To find m, we need to select two arbitrary points on the slope. We will use the no-load and full-load values for y and x. Now, we can calculate the current draw at 150LBS of force by plugging into the formula. The current draw at 150LBS is 7A.

### Calculating Power Consumption

Power consumption based on ideal and actual values may vary due to external factors such as:

• Ambient temperature
• Operating conditions
• Variance in motor build
• Use of third-party control equipment
• Actual applied force

DC power consumption can be calculated by using the following formula:

Power = Voltage * Current

If we want to calculate the power consumption of the PA-04-400LBS when a 150LB load is applied, we can plug the calculated current draw of 7A into the equation. The calculated power draw at 150LB for the PA-04-400LB is 84W.

### Measured Power Consumption

To obtain a true measurement of the power consumption under continuous motion with a fixed applied load, you will need a voltmeter and an ammeter to measure the actual input voltage and current draw.

For example, the input voltage may be 12.2VDC and the current draw may be 7.4A. In this circumstance, the power consumption will be 90.3W.

Comparing the measured vs. calculated current draw, we can determine the percentage change between the two values.

Measured = 90.3W

Calculated = 84W

For a difference of 6.3W, there is a 7.6% power increase based on the measured values when compared to the calculated value.

With this information, you can then safely and accurately measure the requirement for power in your system to allow for sufficient power distribution and safety measures that can be applied.