What Is the Difference Between an AC Motor and a DC Motor?

What Is the Difference Between an AC Motor and a DC Motor?

The differences between AC and DC motors involve the unique characteristics of the two types of electrical currents.

AC motors generally deliver greater power and efficiency than their DC counterparts while DC motors are easier to control. Of course, these are generalizations that are constantly being challenged by new technologies and advanced scientific and engineering developments. Recent advances in the past 10 years have made using AC motors in golf carts practical, affordable and efficient.

Power Source Defines How Motors Convert Electrical into Mechanical Energy

AC motors are powered by alternating current while DC motors use direct current from batteries, power packs, and AC-to-DC converters. Alternating current is the power that utility companies generate for business and residential use, and AC motors are rugged with fewer parts that are exposed to prolonged friction. DC motors use brushes and commutators, which are subject to failure, but the electrical output from DC power sources is very precise.

When using direct current, the electrons flow in only one direction at a steady rate. Unfortunately, DC power can’t travel long distances due to losses of power along the way and voltage limitations. AC motors obtain their power from AC generators and power mains, and the electricity travels forward and backward continuously. This allows transmission of higher voltages over longer distances. Traditionally, golf carts operate on DC power, but that trend is changing as manufacturers are beginning to embrace the benefits of using AC power and motors. You can actually convert your DC motor into an AC motor by discussing the steps with a skilled engineer or hiring one to do the job.

Why AC Motors Perform More Efficiently than DC Motors in Golf Carts

Anyone who has ever driven an electric cart with a DC motor can attest that these carts slow down on hills or when carrying heavy loads. AC motors deliver more power because they tap into current moving in both directions. The problems of using DC electric motors in golf carts include:

  • The brush-and-commutator arrangement of DC motors is subject to increased wear and greater failure rates.
  • Commutators partially convert direct current by reversing each time the coil moves the magnetic field’s plane, which mimics alternating current, so starting with alternating current is more efficient.
  • The windings on DC motor stators generate heat that requires challenging technology to dissipate, which includes oil cooling, etc.
  • Commutator arcing is a common problem.
  • Horsepower and torque can’t match those of AC motors.

The benefits of using AC electric motors in golf carts include:

  • Improved braking power when traveling downhill
  • Lower maintenance costs
  • Higher RPM rates that generate higher top speeds
  • More power for climbing hills and carrying heavy loads
  • Faster acceleration
  • Less internal friction, which means fewer repairs and parts replacements
  • More energy-efficient according to independent studies that show AC motors are up to 39 percent more efficient
  • Greater programming complexity
  • Control of motor speed using pedal position instead of electronic speed controllers

The only reasons why AC motors have been slow to penetrate the market are because of increased costs and complex programming and engineering challenges. Now that these have been solved, the greater initial cost of an AC motor is rapidly dropping to competitive levels.

Nikola Tesla and His Bump-and-Run Approach to Science

Many scientists and engineers consider Nikola Tesla the most underrated scientific genius of all time. Tesla built the first workable AC motor in 1887, and his discoveries laid the groundwork for using AC power generation to deliver electricity to homes and businesses. Thomas Alva Edison, the Wizard of Menlo Park, favored DC power, but his fledgling Edison Power Company faced the challenging task of building generators every few blocks because of the travel limitations of DC power. Edison had previously employed and fired Tesla, so he shared his discoveries with the world. Tesla wasn’t very interested in business practices or even building prototypes–because he could visualize his designs in 3-D, and with his eidetic memory, he knew they’d work once he worked out the details in his head. After solving a problem, Tesla would move on to the next challenge with little interest in building a prototype or exploring commercial applications.

Edison, however, learned early in life to patent his ideas as soon as possible, so he got an incredible head-start in developing electric power commercially. Edison’s chief rival, George Westinghouse, also developed a light bulb, but he hired Tesla for a time and adopted the idea of using alternating current to power homes over longer distances from a central generating station. Edison claimed the biggest share of the electric service business in the big cities where everyone lived in dense accommodations while Westinghouse sold his electric services in the West where distances were great and homes were scarce. Edison sued Westinghouse for infringing on his light bulb design, and the press referred to the lawsuits and countersuits as “The War of the Currents.” The lawsuits between Westinghouse and Edison were actually destroying both companies until the companies merged to form General Electric.

The War of the Currents continues to rage across the world of technology, but alternating current continues to overpower direct current in common electrical power usage and is rapidly gaining traction in direct applications where devices can’t be plugged into the electrical grid. Tesla’s prescience predicted that carts and other devices would use AC motors, but he probably saw no commercial applications for activities and products like golfing and riding around the course on golf carts. Tesla was the prototypical absent-minded genius who had little practical intelligence for dealing with everyday life, yet he challenged Edison’s position as the Industrial Revolution’s premier inventor.

Power for Any Angle of Approach

Although the differences in how alternating and direct currents perform may seem small, they can generate tremendous performance differences in various applications. Continuous alternating current that flows in both directions increases voltage and enables electric circuits to travel vast distances. Varying voltage levels can generate greater horsepower and torque, so golf cars, carts and ATVs have enough power to carry multiple passengers up hills, and advanced control options enable operators a degree of control that rivals DC motors. In fact, AC motors have advanced so significantly over the past decade that they can match the control and precision of DC motors with regen features.

Costs for DC-to-AC Golf Cart Conversions

Conversion kits are now available to convert DC motors to operate on alternating current, and the costs are dropping. DC motor conversions for golf carts work in the following way:

  • The direct current of a 48-volt battery pack is inverted to generate an AC signal to an AC induction motor.
  • The AC motor bolts directly to golf cart differentials.
  • You might need to replace the battery pack if using a 36-volt model.
  • The AC inverter/controller is larger than the DC motor controller, so you’ll need to attach a large aluminum plate to the cart’s frame to seat the assembly firmly.
  • If you’re converting a 36-volt battery pack to a 48-volt pack, you’ll need a 48-volt charger.

The costs of conversions might include upgrading a 36-volt battery pack to a 48-volt pack. The 48-packs can be configured in any combination such as four 12-volt batteries, eight 6-volt cells of six 8-volt batteries. You might need to spend extra for the appropriate cabling harness. AC motor inverter/converter units range from $2,100 to $2,500. The cost of an original golf cart engineered with an AC motor varies, but the costs are dropping as demand for the technology rises.

Overall Distance Standard

AC motors are more efficient, so even if the initial costs of buying a cart with an AC motor or converting a cart with a DC motor are high, you’ll save money on maintenance, energy use and repairs. If converting, you can also realize some value from selling the DC motor/controller after replacing it with the AC controller. Depending on where you use your cart, the increased performance could easily justify any higher costs–especially if you use the cart on hilly terrain or typically carry four hefty golfers. You can go the distance in style and comfort with greater downhill speed control, more torque to climb hills easily and faster speed on flat terrain. Most golfers choose the 18hp AC motor, but other options are available. Your battery configuration will affect the cart’s range. Using eight 6-volt batteries usually provides the greatest range. The 18hp AC motor for golf carts delivers 81 pounds of torque and speeds of approximately 25 mph, but some owners have reported top speeds up to 34 mph.

Managing Your Golf Cart’s Handicap

Golf carts using AC motors can reach smoking-fast speeds on straightaways, and they even negotiate hills with faster-than-DC-motor speed while hauling four passengers. A golf cart running on an AC motor probably won’t improve your golf game, but it could if you’re playing against someone who uses slower and inefficient technology and gets frustrated when left behind. In golf, it’s all about bragging rights, and enthusiasts have been known to spend many thousands of dollars on classic vehicles to use as transportation to the golf course. Golfers love arriving at the course in a restored classic car such as the Cadillacs and Buicks of the 1960s. Unfortunately, these status symbols do nothing to improve transportation around the golf course. That’s why progressive golfers are switching to golf carts with AC motors in unprecedented numbers.


Posted by Geoff Brand


This entry was posted in General.