Premium Membership

Get 15% OFF on Pro Premium Plan with discount code: UX21M. Study specialized electrical engineering articles and papers in Low- and High-Voltage areas.

Home / Technical Articles / How can a PLC and VFD be used for pump control (power and control circuits)

Introduction to PLC/VFD motor control

For the last several decades, every engineering task related to process control is realized by the use of PLC (Programmable Logic Controller). If we are talking about induction motor control, which is the most common case, usually a VFD (Variable Frequency Drive) is electrical device placed “between” a PLC and motor, providing a connection of control logic and circuits on one side, with desired power output at the other side.

How can a PLC and VFD be used for pump control (power and control circuits)
How can a PLC and VFD be used for pump control (power and control circuits)

In that way, these three devices (PLC, VFD and motor), together with field measuring devices, represent one functional whole, capable for control, supply, protection and monitoring of some process consumer driven by induction motor.

In this article, a real example of submersible pump control will be described. Attention will be given to description of electrical devices, signals, and operation principle.

Example of pump control

Submersible pump, which is a subject of this example, is used for WWTP (Waste Water Treatment Plant) inlet chamber level control. Physical appearance of this pump type during installation is shown in Figure 1.

KSB Amarex submersible pump
Figure 1 – KSB Amarex submersible pump

Real time measurement of level is done by ultrasonic level meter placed inside inlet chamber. You can read more about this device in previous article called “Field devices and signals used for LV SCADA operations”.

This real-time value is transferred to PLC (See Figure 6) and compared to the required level value defined by the operator. Based on difference between these two values, required pump flow is calculated using PID control logic. Since pump flow is dependent on pump motor speed (this function is given by pump manufacturer), required flow can be achieved by adjusting a motor speed via VFD which is controlled by PLC.

Wiring diagram of VFD outgoing inside MCC (Motor Control Centre) used for pump control is given in Figure 2.

PREMIUM Membership Required

This technical article/guide requires a Premium Membership. Get access to all premium HV/MV/LV technical articles, electrical engineering guides, and papers. Check out each plan’s benefits and choose the membership plan that works best for you or your organization.

You can choose an annually based Plus, Pro, or Enterprise membership plan.

SPECIAL OFFER – Get 15% Off on PRO premium plan, use discount code: UX21M

Log InSign Up

Premium Membership

Get access to premium HV/MV/LV technical articles, electrical engineering guides, research studies and much more! It helps you to shape up your technical skills in your everyday life as an electrical engineer.
More Information

Miodrag Kokotovic

Graduated from Faculty of Electrical Engineering, within University of Belgrade, in the field of electrical power systems. Expert in electrical part of tender preparation, design, procurement, construction and commissioning of treatment plants and pumping stations, electrical power quality and energy management.

Leave a Comment

Tell us what you're thinking... we care about your opinion!

Electrical Engineering Courses

Learn to design electrical power and industrial automation systems through professional video courses.