Regal Beloit is now Regal Rexnord. Click here to learn more.

Understanding the Demand for Permanent Magnet AC (PMAC) Motors

As the world continues to ask questions such as “how are we using energy?” and “is this energy being used wisely?”, we are seeing increased governmental regulations, a focus on reducing strain on existing infrastructure, lower levels of fossil fuel emissions, and advances in materials and electronics. All these factors are causing the demand for Permanent Magnet AC (PMAC) motors to increase.

PMAC Motors vs. AC Induction motors: What’s the Difference?

When comparing PMAC motors to AC induction motors, one major difference is in the rotor itself. In a squirrel cage induction motor, current is induced into the rotor from the field (stator) through the air gap and conducted through aluminum (or other material) bars, which are most often die cast in the slots of the rotor laminations. In the case of a PMAC motor, the rotor itself contains permanent magnet material, which is either surface-mounted to the rotor lamination stack or embedded within the rotor laminations. In either topology, electrical power is supplied through the stator windings.

The most obvious performance difference is that a PMAC motor rotates at the same speed as the magnetic field produced by the stator windings, meaning it is a synchronous machine. If the field is “rotating” at 1800 rpm, the rotor turns at the same speed. An induction motor, on the other hand, is considered an asynchronous machine. Its rotational speed is slightly slower than the magnetic field’s “speed”. An asynchronous motor is said to have slip. This slip is the difference between the motor’s physical speed of, say, 1750 rpm, and its stator’s magnetic speed of 1800 rpm. It cannot produce torque without this difference in speed, as the rotor is constantly trying to “catch up” with the magnetic field. The synchronization of PMAC motors results in improved efficiency, better dynamic performance, and more precise speed control.

Other performance differences include higher efficiency and power factor in a PMAC motor. Since a permanent magnet rotor lacks conductors (rotor bars), there are no I2R losses, so with everything else equal, a PMAC motor is inherently more efficient.

PMAC motors provide higher flux density than a comparable induction motor. This means more power (torque) can be produced in a given physical size, or equal torque produced in a smaller package. It is very common to see a frame size reduction with PMAC motors.

All commercially available true PMAC motors require a variable frequency drive to operate. While there is on-going research into a "line start PM" motor, all current commercially available, true PMAC motors require a variable frequency drive to operate. There are performance characteristics of this design which have to be taken into consideration.

Comparison of PMAC and Induction Motors:

PMAC Motor AC Induction Motor
Permanent Magnet rotor Die cast rotor
VFD power only Line or VFD power
High power density Low power density
Wider air gap Narrow air gap
Fixed pole count within frame size Varying number of poles within frame size



Benefits of PMAC Motors:

Because of their lower operating temperature, reduced vibration and noise, and improved reliability, PMAC motors provide benefits including energy savings, lower operating temperature, reduced vibration, reduced noise, improved reliability, and application flexibility.

  1. Energy Savings

    PMAC motors are inherently more efficient due to elimination of rotor conductor losses, lower resistance winding, and a flatter efficiency curve. PMAC motors are known to provide even more energy savings at reduced speed.

    Efficiency ratings are 1-3 indexes above NEMA Premium, providing electrical energy savings from day one. This translates to 10-30% fewer losses than a conventional motor and provides quick return on the investment. Since electricity is estimated to comprise approximately 95-97% of the total life cycle cost of electric motors; this energy savings significantly reduce the total investment.


  2. Reliability and Longevity

    Due to their lower operating temperature, PMAC motors require less frequent maintenance and offer longer bearing and insulation life. The robust construction of the SyMAX™ motor is suitable for virtually any application, providing years of trouble-free operation in harsh environments.


  3. Application Flexibility

    Under most circumstances, replacing existing induction motors with PMAC motors requires no mechanical changes to the equipment. Virtually any application suitable for use of induction motors can utilize PMAC motors, with direct drop-in replacement for existing NEMA and IEC motors.


  4. Performance

    Due to their synchronous operation, PMAC motors offer more precise speed control. PMAC motors also provide higher power density due to the higher magnetic flux as compared with induction machines.

Which Applications Could Benefit the Most from PMAC Technology?

Standard induction motors are not particularly well suited for low-speed operation as their efficiency drops with the reduction in speed. They may also be unable to deliver sufficiently smooth torque across the lower speed range. This is normally overcome by using a gearbox. The PMAC motor solution provides a high torque drive coupled directly to the load. By eliminating the gearbox, the user saves space and installation costs, as he only needs to prepare the foundations for one piece of machinery.

Since we don’t see the dropping of efficiency as we slow down as compared to induction motors, PMAC motors work well in commercial HVAC fan applications in data centers, cooling towers, and AHUs.

Talk to one of our expert sales professionals about how our products can efficiently power your business.

As more efficient motors become the industry norm and more companies look to retrofits for energy tax credits, the need for innovative and efficient motors such as PMAC will increase. Understanding your options can help ensure you achieve the lowest total cost of ownership for your electric motors.

This name is used, please enter another
{0} was created successfully.
{0} was deleted successfully.
New password and confirm password do not match.
The password entered does not comply with our password policy. Please try again.
The password entered does not comply with our password policy. Please try again.
You have already access to entered account.
Account already added
Your selected account has been changed probably in different window. Please refresh page and select correct account.
Please select an account
The entered account number is not valid or the account is not yet transitioned for use at
You must provide a valid account number to be added. Please contact your Sales Representative or Account Administrator if you don’t know your Account Number.
Please select Additional Access checkbox.
Please enter your address.
Please enter your address cont.
Please check to agree with Terms of Use and Privacy Policy.
Please enter your city.
Please enter your company name.
Please enter confirm password.
Please select your country.
Please remove the discontinued item from cart to proceed to checkout.
Your order contains discontinued items. Please remove from cart and proceed with rest of the items.
Please enter a valid format for your email address.
Email address required
Please enter your email address.
Please enter your first name.
Please review and select a warehouse for Catalog/Part Numbers: {0}
Please enter your job title.
Please enter your last name.
Please note: Your order contains Made to Order (MTO) items. Return requests on MTO products are subject to review and not guaranteed.
The current password entered does not match your password or new password is the same like one of the previous or password changed last 30 days.
Profile updated successfully.
Error while request access.
Registration Information has been received.   Thank you for your interest in Regal Rexnord.
Please enter new password.
Please enter old password.
Please enter a valid format for your phone number.
Please enter your phone number.
Please enter a valid format for your extension.
Please select at least one product category.
Please verify you are not a robot.
Registration Information has been received.   Thank you for your interest in Regal Rexnord.
Internal users can not request access for customer accounts. If you need access, please route through the customer service representatives.|||
You must provide the name of a Regal Rexnord employee who can confirm your need for access to Genteq technical documents.
Please make sure you enter Sales Order, Quantity, Reason, Part number, Invoice and Line Number fields.
Error submitting request.
Your request has been submitted successfully.
Please select your state.
Please select the training portal role.
This email is already in use. Please log in.
You do not have permission to access this page.
Confirmation code has been sent successfully to your new email address. Please enter the Confirmation code and update the profile.
Email Address has been changed successfully. Please check your email for information to login again.
Verification code required
Please enter your zip code.
Your session has timed out. You must log in again to access secure content. Any work on the current page will be lost.
Your shopping cart qualifies for free shipping.
Minimum order quantity is {0} {1}. Please enter a valid quantity for item: {2} .
Item must be ordered in multiples of {0} {1}. Please enter a valid quantity for item: {2} .
Add {0} more to your cart to qualify for free shipping.
Item {1} has been removed from cart.
You cannot delete Mod Product- {0}.
Add {0} more to qualify for free shipping.
This item is discontinued, but you may order against the remaining inventory. You have requested {4} items of the total remaining quantity of {2}.
The following item(s) have been added to your cart: {0}
Request of quotes should allow items in same segment
Please enter Application.
Please enter Country.
Please enter Email Id.
Uploaded file is not supported, File upload supports word, excel and pdf.
File too Big, please select a file less than 20mb
The item you have entered have no business segment.
The item {1} allow maximum {0} quantity.
The item {1} requires a minimum of {0} quantity.
Please enter Output HP.
Please enter Required Specifications.
Error submitting request.
Your request has been submitted successfully.
Please enter valid product.
The item {1} must be in multiples of {0} quantity.
The {0} you have entered was not found. Please revise.
Please enter Speed (RPM).
Please enter Voltage (V).
File size requires longer download time
File is not found. Please try again or contact customer service.
Check Inventory
Compare Product
Some of the documents are missing. Please review.
Sorry, at this time this product does not comply with the standards of the country you selected.
This product complies with the standards of the country you selected.
One or more items added to your cart are not eligible for return.
I agree to the Terms of Use and Privacy Policy * is required.
Email has been sent successfully
All estimated shipping dates have a local warehouse cutoff time for shipment date shown. This time is displayed to the right of the date.
The account you are currently on does not have access to purchase this product. Please change to your {0} account to purchase.
Key Features
The following item(s) have been moved to {0}: {1}
Quantities over {0} may require additional lead time. A Regal representative will contact you if this occurs.
You can only order in multiples of {0}. Please enter a valid quantity for this item.
You have no products selected for comparison. Please select at least two products to compare using the 'Add to Compare' checkbox found on product list pages or product detail pages.
Sorry, this item is no longer available.
Product Specs
Related Products
Resource Center
Available warehouses not found.
The item requires a minimum order of {0} pieces.
The item requires a minimum order of {0} {1}.
The item must be ordered in multiplies of {0} pieces.
The item must be ordered in multiples of {0} {1}.
Commercial Systems|Industrial Systems