How Does a Permanent Magnet Motor Work?

In an effort to cut down on electric motor energy use, many people are switching from induction motors to more efficient permanent magnet AC (PMAC) motors. Understanding permanent magnet motor technology can help you determine if making the switch is right for your application.

How does Permanent Magnet Motor Technology Achieve Higher Efficiency?

PMAC motors do not rely entirely on current for magnetizing the rotor. Instead, rare-earth magnets are included in the rotor construction. These magnets supplement a portion of the rotor magnetizing current, meaning less magnetizing current is needed to deliver to power to the rotor. This reduces motor input power consumption while keeping the same motor shaft output power--translating to higher motor efficiency! 

Permanent Magnet Motor Advantages Over Induction Motors

When operated with a Variable Frequency Drive (VFD), a PMAC motor can greatly improve system efficiency. The synchronous speed operation of a PMAC motor (also called synchronous AC motors) has better speed control over a typical induction motor. A VFD converts AC to DC power to regulate the intensity of the output. It does this through the use of devices called rectifiers. Rectifiers regulate positive and negative voltages, maintaining the output specified.

An induction motor is typically limited to one or two available speeds that slows with increased load or temperatures. VFDs are capable of a range of speed options, opening the door to:

• Potential automation compatibility
• Remote operation (via Bluetooth or WiFi)
• Sensor monitoring
• And other higher-level features not available with simple induction motor.

PMAC motors have guaranteed efficiency and torque over a wide speed range with specific power outputs. They can produce a lower energy bill because PMAC motors consume less power; even exponentially less power is consumed at lower speed settings. In addition, far less power is consumed than the older, less efficient limited-feature AC induction motors. That’s where efficiency and power consumption become even more significant, making PMAC motors ideally suited for variable speed applications. The best part? Return on investment typically occurs in 12 to 24 months.

Permanent Magnet Technology Offers Even More Benefits

Additional benefits of a permanent magnet motor include reduced noise and less vibration by running at lower speeds throughout the day. Plus, permanent magnet motors are often totally enclosed and suitable for mounting in all angles. Marathon® SyMAX® PMAC motors meet standards such as UL, CSA and CE electrical and mechanical requirements. They are backed by a three-year warranty which means you can have peace of mind knowing that your applications will continue to operate when needed.

A permanent magnet motor runs cooler than a typical induction motor. Heat is a motor’s worst enemy. The PMAC motor design reduces rotor loss which significantly reduces operating temperature.

Switching to a Permanent Magnet AC motor can also help you achieve a lower total cost of ownership. You’ll see longer maintenance intervals as well, and increased service life of the entire drive system since power transmission devices such as pulleys, belts and gear reducers have been simplified or removed.

As more efficient motors become the industry norm, the need for improved efficiency will continue to increase. The variable speed capability makes PMAC motors the motor of choice in many applications. Do you think PMAC motor technology can be a benefit to your product or system? Contact one of our motor experts today.