When you're looking for an electric motor for any industrial application, you'll hear the same question — AC or DC? If you're based in the United States, your default answer might be AC because that's what most buildings are set up to handle, but are they really the best choice? Let's take a look at the advantages of DC motors in industrial applications and whether you should choose to make the switch.
Types of DC Motors
When it comes to DC motors, you've got five options. First, you need to decide if you want a brushed or brushless motor. If you opt for brushless, which has a longer lifespan for high-use applications, your decision is complete. If you opt for a brushed motor, you now have four choices:
Series wound: Field winding connected in series to provide varying voltage but doesn't offer much speed control
Shunt wound: Field winding connected in parallel for more torque and speed control
Compound wound: A combination of shunt-wound and series-wound motors
Permanent magnet: Uses a permanent magnet rather than an electromagnet
Each type of motor works well for different applications, so start by researching the right type of motor for your specific needs. Are you already set up for DC motors? Will swapping your DC motor out for an AC motor make your machinery more efficient or productive? What makes DC motors better than AC options in industrial applications?
Higher Starting Torque Than AC
DC motors have higher starting torque than their AC counterparts, making it easier to get things moving. The only problem with these motors is that you can't start them unless they're already under a load. Without a load to slow them down, DC motors can burn out quickly. For applications that need constant low-speed or variable-speed torque, DC motors are ideal.
Linear Speed-Torque Curve
The torque equation of an induction motor — or the curve plotted between the torque and speed of said motor — explains the relationship between how fast the motor spins and how much torque it can generate. DC motors generate a speed-torque curve that's much more linear than AC motors.
No Harmonic Effect
AC motors are susceptible to harmonic effects that can damage the equipment or cause the iron or copper components to heat dangerously. In addition to causing excessive noise, harmonic problems can cause the motors to fail prematurely or misfire during use, damaging other equipment or upsetting the manufacturing process. DC motors don't have this problem, effectively eliminating the issue.
Improved Speed Control
DC motors offer better speed control than their AC counterparts. If you're working with heavy load systems, the ability to control the speed precisely can mean the difference between a successful job and a burned-out motor. That's why they're often employed in paper mills and rolling mills where speed needs to be kept consistent to ensure constant product quality. DC motors are ideal for any job that needs constant low-speed torque or adjustable torque.
Easier Installation and Maintenance
DC motors are easier to install than AC motors, require less maintenance and are easier to repair than their AC counterparts. Many industrial systems may already be set up to use DC motors. If that's the case, replacing a failed motor with another DC model is quick, easy and painless. Replacing it with an AC model will require you to redesign the entire motor circuit.
DC motors are relatively simple, making maintenance and repairs easier.
Choosing DC Over AC
For industrial applications that require constant low-speed torque or precise speed adjustments, DC motors are likely going to be the best choice. They're easier to maintain and provide superior speed control while eliminating the problems caused by harmonic effects. They also have higher starting torque than AC motors, though you can't start DC motors unless they're already under a load — they spin up so quickly that it could burn out the motor.
If your facility is already set up to use DC motors, switching to AC would require you to rewire the entire motor circuit. Instead of wasting all that time and effort, simply rely on the classic DC motor. DC motors are capable of providing nearly any industrial application with the power and torque it needs to succeed.