Digital Twin of a Motor and Pump System – Second Edition

About a year ago, my colleague, Eric Bantegnie, wrote a blog that described how we, along with our partners PTC, NI and HPE, had created a digital twin of a pump and one of its valves. We showcased this at PTC LiveWorx. I’m happy to announce that work continues with our partners on a new and expanded version of the digital twin of this pump and its valves to its motor and electric drive.

Why is this exciting and important? This enhanced digital twin demonstrates a multi-domain system including fluids, electromechanical, electromagnetics and thermal  aspects, coupled with a user friendly Human Machine Interface (HMI),  to solve a challenging problem that faces motor designers and operators — determining, monitoring and maintaining the optimal temperature at which to operate the motor and its components on a consistent basis. Why does this matter? Every 10 degree Celsius increase in operating temperature of the motor and components over their optimum temperatures decreases the life of the motor by half!

But how can an operator determine if the motor is consistently running at its optimum temperature and not overheating? Often there are no sensors on the motor to provide information about the temperature of the motor. Operators can guess at what temperature the motor is by monitoring the input power, current and voltage, but this is an imprecise method.   When motors are deployed in the field, even if there are sensors measuring temperature, they are costly to operate and data is frequently inaccurate or delayed.

Determining Motor Temperature

A digital twin can provide answers to this important question, extending the life of the motor by ensuring the motor temperature is within the desirable range while the pump operates at around its best efficiency point. How does this work?  Flow and pressure have an impact on the operation of the motor and the temperature at which it operates. The physical pump is connected to the motor driven by the electrical controller. With the digital twin, only two inputs from two sensors that indicate the opening position of the two flow valves controlling flow rate through the pump, are needed to simulate the entire system — allowing us to gain useful insights into the operating conditions of the pump and motor. By utilizing virtual sensors embedded in simulation models, the need for physical sensors can be drastically reduced. With the digital twin and the information from the two sensors on the pump, we are able to determine the temperatures of the motor in addition to the current, flow rate and pressure at various locations at all times.   

Building and Connecting the Digital Twin

In order to create the simulation models necessary to build the digital twin and determine the operating temperature of the motor, a system-level, multi-physics approach that combines fluids, electromechanical, electromagnetics and thermal simulations is necessary. Remember that the pump is connected to the motor and the motor is driven by a controller.

In addition to the electromechanical model of the motor, we created a thermal Reduced Order Model (ROM) of the motor with the inputs to the motor being the voltage and current, and the output being the temperature. This requires first an electromagnetic simulation of the components within the motor to calculate the heat sources within the motor itself. Then, these results are passed to a CFD simulation to determine the cooling aspects. In the above process, two ROMs are created, the first one for motor electromagnetics and the second one for cooling, enabling quick predictions of both the transient and future steady state temperatures of the components of the motor.

system-level model of the digital twinThe system-level model of the digital twin
incorporates multiple physics and an HMI. (click image to enlarge)

Once the as-designed digital twin is ready, we can connect it to the physical pump and gather sensor data to determine the operating conditions of the pump and the motor and make adjustments as needed to maintain optimum motor temperature. But, we can do even more than this. When we disconnect the digital twin from the physical asset, we can use ANSYS simulation and HMI to test different scenarios and operating conditions of the digital pump and motor. By digitally manipulating the valves on the pump, we can immediately see how these changes affect the flow, discharge and suction pressures, current, and temperature of the motor’s rotor cage and the bearings inside the motor. This allows the pump operator to perform what if scenario testing, putting the digital version of the motor-pump through its paces to find optimal operating conditions for both the motor and pump, and perform corrective actions.

Normal Condition

Overheat Condition

Predicting the Future With Digital Twins

The digital twin allows the operator to determine the future state of the motor components’ temperatures too. This is extremely useful information that cannot be determined without the use of a digital twin. Due to the thermal mass of the motor components, it takes time for their temperature to change. For example, if the motor is in an environment with high ambient temperature or in an overload condition, the operator may not know that there will be a temperature spike on the motor components until it actually happens some time later, if there are temperature sensors on the motor. If there are no temperature sensors on the motor, the operator would never receive this information. By being able to predict the results of certain changes in the ambient temperature, pump, fluid or flow and how they will affect the temperature of the motor and its components immediately, the operator can take corrective action early, helping to preserve the life span of the motor and its components. The digital twin enables all of this.

If you are going to be at PTC LiveWorx, swing by Booth 345. We’ll be demonstrating a real life motor-pump digital twin in our booth. Also, learn more about how we are partnering with PTC to enable digital twins and how simulation can solve the challenges of ever increasing digitalization. We’ll be presenting on this topic at the show.

And learn more about how we are powering simulation-based digital twins in the most recent edition of ANSYS Advantage magazine.


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