June 11, 1996

James Raba

Energy Conservation Program Specialist

Office of Codes and Standards EE43

U.S. Department of Energy

1000 Independence Ave., S.W.

Washington, DC 20585

RE: Exemptions to the Energy Policy Act on Electric Motors

Dear Mr. Raba:

SEW-Eurodrive, Inc. is a large international and domestic manufacturer of industrial gearmotors. We

manufacturer three-phase induction NEMA design B motors as an integrated part of our gear

reducers. The motor shaft and flange are physically part of both the reducer and the motor (this

concept is shown in Figure 1).

Gear reducer

Figure 1

The integrated design and manufacturing of the reducer and motor package provides our customer a

number of distinct advantages compared to purchasing a stand alone reducer and motor from two

different companies. A gearmotor system as a package may well be more efficient and provide less

energy consumption than an energy efficiency motor and reducer sold separately.

q MIDWEST FACILITY O WEST COAST FACILITY SOUTHEAST FACILITY O NORTHEAST FACILITY q SOUTHWEST FACILITY

2001 WEST MAIN ST. 30599 SAN ANTONIO ST. AND CORPORATE OFFICES 200 HIGH HILL RD. 3950 PLATINUM WAY

TROY, OH 45373 HAYWARD , CA 94544 1275 OLD SPARTANBURG HWY. PURELAND INDUSTRIAL COMPLEX DALLAS, TX 75237

TEL: 513-335-0036 TEL: 510-487-3560 P.O. BOX 518 BRIDGEPORT, NJ 08014 TEL: 214-330-4824

TEL: 513-461-4797 FAX: 510-487-6381 LYMAN, SC 29365 TEL: 609-467-2277 FAX: 214.3304724

FAX: 513-222-4104 TEL: 803-439-7537 TEL: 215-563-3575

FAX: CORPORATE 803-949-3039 FAX: 609-845-3179

SALES 803-439-0566

EE-RM-96-400 COMMENT 01
RE: Exemptions to the Energy Policy Act on Electric Motors

May 29, 1996

Page 2

The first point that will adversely effect a gearmotor's motor efficiency is the use of a radial shaft oil

seal on the motor shaft. This seal is critical to proper motor operation since the gear reducer contains

gear oil and the motor shaft is a so-called wet shaft meaning that the motor shaft is exposed directly to

oil. The motor oil seal prevents oil from entering the motor. The down side to the oil seal as part of

the motor is that the oil seal friction can significantly reduce the motor's efficiency particularly at low

motor powers. It is important to realize that this seal will be present in the reducer if it is not present

in the motor. So in any case there is a reduction in system efficiency caused by this essential oil seal.

In a gearmotor the seal will be in the motor and reduce its efficiency. In a separate reducer and

motor the seal will be in the reducer and reduce its efficiency.

Additionally as added environmental protection we produce a large percentage of our motors with

double sealed bearings and a V-ring on the rear of the motors. These additional protection devices

are required for a large number of our applications in order to ensure that the motor is suitably

protected from its environment. The down side to this additional mechanical protection is that it also

adds to the motor's frictional losses.

There is a second issue that differentiates the design of our motor, and many other gearmotors, from a

standard NEMA frame motor. This is our motors ability to cycle on and off. This ability is referred

to in NEMA MG1-1993 Part 20.43.1. The NEMA recommendation is that an induction motor be

able to start two times successively if the motor is cool and one time if the motor is hot. A primary

goal for SEW motors, and many other gearmotors, is to be able to start and stop often. For example

our standard 1-hp 4-pole motor is able to start 7500 times per hour if the motor is unloaded and as the

load is increased the number of starts per hour is reduced. In order to achieve these large number of

starts without having premature motor failure some of our basic design is different than a standard

NEMA frame motor. One key design point is that the motor's rotor must have a very low inertia. In

general our rotor is much smaller in diameter and slightly longer than a typical NEMA motor of the

same rating. This design allows our rotor to have a much reduced inertia. Having a reduced inertia is

one key to a high number of starts. The larger the motor's rotor inertia the longer it will take to

accelerate to its operating speed. The longer the motor takes to accelerate the hotter the motor will

get. The starting current in an induction motor is much higher than its full load current. So the

longer the motor is in this high current starting phase the longer it will draw a much higher current.

The drawback to designing a rotor with a low inertia is that the magnetic iron content in the rotor will

also be reduced. This reduced iron content will also reduce the motor's efficiency. In order for us to

design a motor to meet the Energy Policy Act's efficiency levels, our motor would have to undergo a

significant philosophical design change. This design change would be to increase the motor's iron

content which in turn would increase our rotor inertia and in turn would greatly degrade our motor's

cycling capacity.

EE-RM-96-400 COMMENT 01
RE: Exemptions to the Energy Policy Act on Electric Motors

May 29, 1996

Page 3

List of motor types we believe should be exempt from efficiency requirements:

Gearmotors - reasons

• Additional losses in sealing system

Covered previously

• Motor commonly designed for low rotor inertia for cycling applications

Covered previously

• Motors are designed in a physically small package size

One benefit of gearmotors is that they are a small physical system. A gearmotor design

reduces the size of the motor and reducer package. This is true since the motor is

physically part of the reducer. As a result, the motor for a gearmotor is often designed in

a small physical volume. This is so the entire product can fit into tight spaces. If the

motor section of a gearmotor was required to be energy efficient, the motor package size

would need to be larger to contain enough copper and core iron. This increased size motor

conflicts with the goal of having a gearmotor, a small package size.

Brakemotors - reasons

• Brake motors are often used in high cycling applications

Covered previously

• Additional brake wear

Due to the larger rotor inertia required to increase the motor's efficiency there will be

more wear on a mechanical motor brake. The motor brake must stop both the motor and

the load. The more inertia in the system, either motor or load or both, the more energy

the brake must dissipate to stop the system. This dissipated energy causes brake wear. So

the larger the rotor inertia the more brake wear that will occur.

Motors with high cycling capacity - reasons

Covered previously

In conclusion it is our concern that if we were required to redesign our motors to meet the efficiency

guide lines in the Energy Policy Act that our motors would suffer a significant degradation in

performance. This performance loss would greatly effect our ability to satisfy our customer's current

applications and in the future would be even more limiting.

Sincerely,

Mark A. Jones

Product Training Manager

EE-RM-96-400 COMMENT 01