Do you know what circumstances are best for pairing a control with a motor? When is it a necessity rather than a perk? In this blog post, we’ll talk through some instances when adding a control is the best solution for you. We’ll also discuss some basic advantages of using a control, as well as a few considerations to make.
Controls with DC Motors
DC motors are known for providing high torque without the lagging that occurs with AC motors. However, because they run on direct current—battery powered rather than the 115/230v alternating current found in standard wall outlets—they aren’t a practical solution for some applications where power options are limited. By using a control with your DC motor, you can plug it into readily available AC power, and the control will convert the voltage to DC, to effectively drive your motor. Additionally, utilizing the right control will allow you to adjust the shaft speed of your motor. If all you are needing is a voltage conversion, then a rectifier is a better option for you to use.
Controls with AC Induction Motors
3 Phase AC induction motors can be driven by a variable frequency drive (VFD). A VFD can control the speed of an induction motor by varying the frequency and voltage of the power to the motor. VFD’s come with a variety of options and you can buy VFD’s that are powered by either 3 phase or single phase power. This can be useful because it allows you to use a 3 phase induction motor even when you only have single phase power available. So in this situation using a single phase input VFD with a 3 phase motor would not only give you speed control but also provide higher efficiency, higher starting torque and all the other advantages that 3 phase motors provide over single phase motors.
Controls with Brushless DC Motors
Brushless DC motors are unique in that they require a control to operate due to them being electronically commutated. A BLDC motor is usually built with a hall effect or other type of sensor that collects internal feedback of how the motor is running. By using a control with your brushless motor, the information from the feedback device is sent to the control so it can send the proper voltage or current waveform to the motor for proper operation.
Controls with Encoders
Feedback devices such as encoders are often added to motors to provide information about how the motor is operating. This is known as “closed loop”. This is often done without using a control, but it is less beneficial to operate that way. By adding a control, you can adjust the performance of a motor while it is operating such as stabilizing the shaft speed as varying loads and quick changes are made to the motor shaft. For example, if you are operating a conveyor that suddenly has a heavy box thrown onto it, it is likely the conveyor will slow down to compensate for the extra load. However, by adding a control to your motor/encoder, the set will “communicate” the slow down and automatically adjust to keep the conveyor pace the same. If you don’t have an encoder in your system or your encoder is not sending feedback, then this is known as “open loop”.
Advantages to Using a Control
Controls are great when your application handles a variety of loads, speeds, etc. Depending on the complexity of your control, you may be able to program it to adjust the speed, direction, and voltage of a motor as it is operating. The flexibility of using this type of control allows the same motor to operate under variations that would typically need two or more different motors.
Oftentimes, due to intermittent loading within certain applications, a smaller motor can be used when it’s paired with a control. This provides more flexibility with an application’s design, features, etc. without giving up the necessary motor performance often found in larger motors. Additionally, smaller motors are typically less expensive than larger motors.
Utilizing a control can also decrease your overall energy use. Some applications without a control require a motor to run continuously at full power so that input from an operator is not required to keep things moving. One example might be a fan. If a fan is required to run only when conditions get hot, and a control is not used, someone may just flip the fan to always “on” so they don’t have to manually hit the switch when conditions get hot. This keeps the motor running non-stop even when cooling may not be needed. If you incorporate a control with feedback and a temperature sensor, an operator could walk away and let the control turn the motor on only when conditions require cooling. Using this process reduces the power used which keeps batteries running longer, improves system efficiency and saves money in the long run.
Adding the right control to your motor can also add an extra layer of protection by setting current limits for the motor. Current limits help protect the motor from overloading by reducing the input current, ultimately keeping the motor from overheating if an unexpected large load is placed on the motor.
Considerations with Using a Control
Adding a control to your motor adds another part in your system, so it generally increases the initial cost investment. Depending on the application, this cost can easily be recovered over time because it improves system efficiency, reduces manual operator input and adds features to your system.
One thing to consider is what level of ingress protection you need your motor and control to have against dust and water—the IP rating. Controls typically offer lower levels of ingress protection than what motors can have—Groschopp controls range from NEMA 1 (IP10) to NEMA 4X (IP55). Pairing a motor with a control can be a challenging task. At Groschopp we can help you select the correct motor and control combination for your application, assist with wiring and hookup and get you started on a solution that works best for your needs. Give us a call and let us help you with your motor project!
