How to Choose a Replacement Electric Motor

Replacing an industrial electric motor does not always require finding the exact same manufacturer or model number. In many applications, a properly selected motor from another manufacturer can be a direct replacement.

The key is knowing which specifications need to match.

PTJ Industrial supplies industrial electric motors in a wide range of horsepower, RPM, voltage, frame and enclosure configurations.

What Information Do I Need to Replace an Electric Motor?

Start with the motor's nameplate. The most important information usually includes:

For many common industrial motors, the HP, RPM, voltage, phase, frame and enclosure will quickly narrow down the available replacements.

1. Match the Horsepower

The replacement motor normally needs to provide the horsepower required by the driven equipment.

For example, if your existing motor is rated 20 HP, you would normally begin your search with a 20 HP replacement rather than simply choosing a motor based on physical size.

PTJ Industrial carries a large selection of 20 HP electric motors as well as motors ranging from fractional horsepower through several hundred horsepower.

Do not increase or decrease motor horsepower without considering the requirements of the equipment being driven and the electrical system.

2. Check the Motor RPM

Common industrial AC motor speeds include approximately:

The actual nameplate RPM will usually be somewhat lower than the motor's synchronous speed.

For example, a motor commonly referred to as an 1800 RPM motor may have a nameplate speed around 1750 to 1780 RPM.

This does not necessarily mean you need to find another motor with the exact same nameplate RPM. The motor's pole configuration and application requirements are what matter.

Changing to a substantially different speed can change the performance of pumps, fans, conveyors, compressors and other equipment.

3. Match the Voltage and Phase

Check the voltage shown on the existing motor.

Common three-phase industrial motor voltages include:

Many industrial motors are dual-voltage, such as 230/460V.

Also confirm whether the motor is single phase or three phase.

A three-phase motor cannot simply be replaced with a single-phase motor of the same horsepower without considering the electrical system and application.

4. Find the NEMA Frame Size

The NEMA frame number is one of the most important pieces of information when replacing an industrial motor.

Common examples include:

NEMA frame standards define important mechanical dimensions such as mounting-hole locations, shaft height and shaft dimensions.

That means motors from different manufacturers using the same NEMA frame can often be mechanically interchangeable when the other required specifications also match.

For example, a properly specified 286T motor from one manufacturer may be able to replace a 286T motor from another manufacturer.

Always verify the complete dimensions and specifications before installing a replacement.

5. Check the Motor Enclosure

ODP - Open Drip Proof

ODP motors are commonly used in relatively clean, dry indoor environments where adequate ventilation is available.

TEFC - Totally Enclosed Fan Cooled

TEFC motors are widely used in industrial environments and provide greater protection from dirt, dust and moisture than an open motor.

Severe Duty

Severe-duty motors are designed for demanding industrial environments and may incorporate additional protection against contaminants, corrosion, vibration and harsh operating conditions.

Explosion Proof

Explosion-proof motors are designed and rated for specific hazardous locations.

An explosion-proof motor should only be selected after confirming the required hazardous-location classification and motor approvals.

Washdown and Stainless Steel

Washdown-duty and stainless-steel motors are commonly used where equipment is regularly exposed to water, cleaning chemicals or sanitary washdown procedures, including food, beverage and pharmaceutical applications.

PTJ Industrial carries stainless steel washdown electric motors for demanding washdown applications.

6. Check the Mounting Configuration

Two motors with the same horsepower and RPM are not necessarily mechanically interchangeable.

Determine how the existing motor is mounted.

Common configurations include:

Pump applications may require specialized configurations such as JM or JP pump motors.

PTJ Industrial carries JM and JP close-coupled pump motors for a variety of pump applications.

7. Check the Shaft

Shaft dimensions are especially important when the motor connects directly to a coupling, gearbox, pump or other driven equipment.

Verify:

NEMA frame standards help standardize many of these dimensions, but specialized motors can have different shaft arrangements.

Can I Replace One Motor Brand With Another?

Often, yes.

A Baldor, WEG, TECO-Westinghouse, Marathon, Hyundai, North American Electric or another industrial motor does not necessarily have to be replaced with the same brand.

The important consideration is whether the replacement motor meets the necessary:

PTJ Industrial can help cross-reference an existing motor to suitable alternatives from the manufacturers we supply.

Can a 1750 RPM Motor Be Replaced With an 1800 RPM Motor?

"1800 RPM" is commonly used to describe a four-pole, 60 Hz AC motor.

Because induction motors operate with some slip, the actual full-load nameplate speed may be approximately 1750 to 1780 RPM rather than exactly 1800 RPM.

Therefore, seeing 1750 RPM on an existing motor does not automatically mean that a motor marketed as 1800 RPM is the wrong replacement.

The complete motor and application specifications should still be checked.

Can I Replace an ODP Motor With a TEFC Motor?

Sometimes, but enclosure type should not be considered by itself.

A TEFC replacement must still meet the required horsepower, RPM, voltage, frame, mounting, shaft and application requirements.

The operating environment and cooling requirements should also be considered before changing motor enclosure types.

Special Applications Require Additional Information

Some applications require specifications beyond basic horsepower, RPM and frame size.

Pumps

JM or JP frame and shaft configuration may be important for close-coupled pump applications.

Rock Crushers and Aggregate Equipment

Crusher-duty or severe-duty construction may be appropriate depending on the equipment and environment.

PTJ Industrial offers a large selection of crusher-duty electric motors for rock crushers and aggregate equipment.

Fans and Blowers

Speed, torque and load characteristics should be considered when selecting a motor for a fan or blower.

Conveyors

Starting torque, duty cycle and gearbox requirements may affect motor selection.

Food and Beverage Equipment

Washdown construction, stainless steel and appropriate ingress protection may be required in food, beverage and pharmaceutical applications.

Hazardous Locations

The motor must have the appropriate hazardous-location rating for the installation.

VFD Applications

Confirm that the motor is suitable for inverter or VFD operation and the application's required speed range.

Don't Know What Motor You Have? Send Us the Nameplate

You do not have to determine every specification yourself.

Take a clear picture of the motor's nameplate and send it to PTJ Industrial.

If possible, also provide:

Our team can use this information to help identify your existing motor and locate an appropriate replacement from our available inventory.

Shop Industrial Electric Motors

PTJ Industrial supplies electric motors for a wide range of industrial and commercial applications, including general-purpose, severe-duty, crusher-duty, pump, IEEE 841, explosion-proof, washdown and stainless-steel motors.

Our online catalog includes detailed specifications, current pricing and available inventory for many models.

Need help finding a replacement motor? Call PTJ Industrial at 800-724-2961 or send us your motor nameplate information.