# About Electric Motors

AC Motors— The choice for fixed-speed, constant-torque applications. Voltage Phase— Single-phase AC motors are less efficient than three-phase AC moto rs, but usually cost less and operate on a more commonly available power supply such as 115/208-230 VAC, 60 Hz.

Three-phase AC motors have higher starting torque, higher efficiency, and lower current draw compared to same size single-phase AC motors, but they require a less readi ly available 208-230/460 VAC, 60 Hz power supply. They usually don't need capacitors, switches, or relays for start-up and are better for heavy duty applications.

DC Motors— Often used where adjustable speed control is require d, DC motors have high starting torque and consistent speed/torque over the entire speed range. DC gearmotors have lower rpms and higher torque.

Keyways— Motor shafts with keyways have standard ANSI keyways. See page 1160 for keyway dimensions. Overload Protection— An internal thermostat autom atically shuts off the motor when it begins to overheat. Manual overload protection has a manual reset button to restart motor. Automatic overload protection allows motor to restart itself once it has cooled.

% Full Load Efficiency— How well a three-phase motor converts electrical energy into mechanical energy. For example, a 70% efficient motor drawing 400 watts produces 280 watts of us eful energy (400 x 0.70 = 280) and loses 120 watts as heat.

Service Factor— The maximum safe load a motor may be expected to consis tently carry. For example, a service factor of 1.35 means that the motor is capable of 35% more hp than its listed rating without damage.

Insulation Class— The maximum temperature a motor can withstand before ma lfunctioning. It's the sum of the motor temperature and ambient temperature. The later the lett er is alphabetically, the higher the temperat ure rating. Most of our motors are Clas s A (rated to 221° F), Class B (rated to 266° F), Class F (rated to 311° F), or Class H (rated to 356° F). 

# Guidelines for Replacing a Motor
When replacing an existing motor, take a look at the spec ifications on your motor's nameplate and match them to the specifi cations

of our motors. The following are some specifications you must consider:



# NEMA 56 Base-Mount AC Motors

Single Phase Open Dripproof (ODP) Enclosure with Rigid Base

Three Phase Totally Enclosed Fan-Cooled (TEFC) Enclosure with Rigid Base All of these motors have a NEMA 56 footprin t with variations as noted. They're rated for continuous duty and have ball bearings (except for 5990K92 and 5990K94 , which have sleeve bearings), Class B insulation rated to 266° F (unless noted), and lead wires for electrical connection (except for 5990K14
, 5990K17
, 5990K21
, 5990K92
, 5990K31
, and 5990K94 , which have a terminal board electrical connection). The motors can be used in either clockwise or counterclockwise rotation; instructions are included. Full load amps shown are at the motor's lowest voltage. Housing is steel.

Single-Phase Motors— These motors have a "start" capacitor to boost the starting torque 200-400% of the ra ted load, unless stated otherwise. They're more efficient than split-phase motors. Capacitor start/capacitor run motors have a "start" capacitor as well as a "run" capacitor for higher efficiency and lower operating temperatures. Model 6223K49 is a permanent split-capacitor motor. It has a capacitor in the circuit to store energy and offer a low starting torque that is 30-150% of the rated load. Use it for high-cycle applications such as direct-drive fans and blowers (it must be mounted in the fan's airflow for proper cooling).

Three-Phase Motors— Have higher starting torque, higher efficiency, and lower current draw compared to same size single-phase motors. They usually don't need capacitors, switches, or relays for start- up and are better for heavy duty applications.

Open dripproof (ODP) enclosures are for reasonably dry, cl ean, well-ventilated, and usually indoor environments. Totally enclosed fan-cooled (TEFC) enclosures offer 

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# NEMA 56 Base-Mount AC Motors

greater protection from the environment than ODP models. They have no vent openings and are cooled by an external fan. Though not airtight, they're suitable for nonhazardous, dirty, damp (but not washdown) environments. Totally enclosed nonventilated (TENV) enclosures are similar to TEFC, but have lower hp and rely on cooling without a fan. Totally enclosed air over (TEAO) enclosures are for use within the airflow of a blower or fan they're driving.

Rigid-base motors have a heavy-gauge base that's welded to the housing for maximum support. Resilient-base motors have rubber isolation rings between the motor mounting hubs and base to dampen vibration and shock. Single-Phase Motors Full VAC @ O'all Load Service hp rpm 60 Hz Lg. Amps Factor Each 

### Open Dripproof (ODP) Enclosure Rigid Base with No Overload Protection 1/2 1725 115/208-230 9.99" 8.8 1.25 5990K26 $164.59 1/2 3450 115/208-230 9.99" 6.8 1.25 5990K47 121.02 3/4 1725 115/208-230 10.99" 10.8 1.25 5990K49 212.53 3/4 3450 115/208-230 10.49" 9.8 1.25 5990K48 157.28 1 1725 115/208-230 10.88" 12.8 1.15 5990K52 220.02 1 3450 115/208-230 10.84" 12.0 1.25 5990K51 205.16 1 1/2 3450 115/208-230 10.84" 16.4 1.15 5990K53 244.56 Rigid Base with Manual Overload Protection 1 3450 115/230 11.38" 13.4 1.15 5990K13 • 205.46 1 1/2 1725 115/208-230 11.84" 17.2 1.15 5990K54 * 298.74 2 3450 115/230 11.88" 22.0 1.15 5990K27 • 239.17 3 3450 230 12.38" 15.0 1.15 5990K28 •‡ 223.28 Rigid Base with Automatic Overload Protection 1/4 1725 115/208-230 9.24" 5.4 1.35 5990K42 142.60 1/3 1725 115/208-230 9.24" 6.6 1.35 5990K12 167.87 1/2 1725 115/208-230 9.99" 8.8 1.25 5990K15 192.99 3/4 1725 115/208-230 10.99" 10.8 1.25 5990K19 219.35 1 1725 115/208-230 10.88" 12.8 1.15 5990K23 251.65 Resilient Base with Automatic Overload Protection 1/3 1725 115/208-230 11.07" 6.6 1.35 5990K14 163.57 1/2 1725 115/230 11.34" 8.6 1.25 5990K17 179.03 3/4 1725 115/208-230 11.07" 11.0 1.25 5990K21 219.91 3/4 3450 115/208-230 11.07" 9.2 1.25 5990K92 • 183.30 1 1725 115/208-230 11.87" 12.6 1.15 5990K31 o 240.10 1 3450 115/208-230 11.44" 12.0 1.25 5990K94 218.92

• NEMA 56Y frame.

* NEMA 56H frame; capacitor start/capacitor run. ‡ Class F insulation rated to 311° F. • Class A insulation rated to 221° F.

o NEMA 56Z frame. (Continued on following page)

1004 

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