RIBXGTA-ECM Current Sensor for Electronically Commutated Motors

Here at Functional Devices, we have many functional devices. One of those devices is the RIBXGTA-ECM. According to Wikipedia, ECM either stands for Equity Capital Markets or Electronically Commutated Motor. Economics was not my best subject so let’s stick with talking about the motors. If you need to send the run status of an ECM to your building automation controller, look no further than the RIBXGTA-ECM! Well, actually don’t stop looking, the blog post isn’t over. Let’s learn about “hysteresis.”

What is an ECM?

An Electronically Commutated Motor (ECM) is also known as a brushless DC motor and is driven by a specially programmed microcontroller that alternates the DC voltage signal to spin the motor shaft. With a “brain” behind the action of the motor, less current is consumed, which results in cost savings. This “brain” needs a constant source of power to keep it ready to receive instruction to turn the motor on. This constant flow of current may be called stand-by current, or leakage current. Stand-by current can cause false-positives with standard current sensors.

Can I use any old current sensor?

Customers love the RIBXGTA-ECM due to its convenient split core housing and low 0.25A minimum trip threshold. However, the feature that really sets it apart from other current sensors and makes it great for ECMs is the ability for it to detect the slight difference between an ECM’s stand-by current and the ECM’s run current. This is what we in the biz call a small hysteresis band. Let’s say you’re installing an ECM for a furnace blower motor. Maybe you’re using a 120V 1HP motor with a dirty air filter. That ECM motor’s current draw is going to get pretty high. If the stand-by current for your ECM is 0.25A, and the motor’s run current gets to 4A, then you would actually be able to use most of our line of current sensors to detect the motor state. On the other extreme, maybe you just cleaned out the air filter leading to a low external static pressure. Maybe you’re using a fractional HP motor running off 277V. The run current will be very low. If the stand-by current is 0.25A and the run current is 0.35A, you might run into trouble with a standard current sensor. For something like an RIBXKTF, a larger hysteresis is a good feature to have because it prevents the feedback state from oscillating if the motor current is hovering around the advertised 0.25A trip point. But in this particular ECM’s case, that large hysteresis combined with the relatively high stand-by current might prevent the RIBXKTF from turning off ever.

Where can I get more information or request a sample?

We have set up an overview page specific to this model, featuring downloads and further information. For more product details, or to request a sample, visit the page by clicking here.

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Noah Smith

Noah Smith, or as his friends call him "Noah", is a design engineer at Functional Devices. He graduated from Indiana University in 2018. Just kidding, he graduated from the superior Purdue University with a Bachelors degree in Electrical Engineering in 2018.

Outside of work, Noah spends his time fantasizing about going back to work. He is a seasoned traveler, having visited almost two states. His weekends are spent with his wife and what has been described as "too many cats."

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