Rockwell Automation FlexPak Plus NRG DC Drive User Manual

Page 15

WARNING

DANGER

THE MACHINERY BUILDER IS RESPONSIBLE

FOR INSURING THAT DRIVEN MACHINERY, ALL

DRIVETRAIN MECHANISMS NOT SUPPLIED BY

RELIANCE ELECTRIC AND PROCESS LINE MAĆ

TERIAL ARE CAPABLE OF SAFE OPERATION AT

MAXIMUM SPEEDS. FAILURE TO DO SO CAN

RESULT IN DESTRUCTION OF MECHANISM OR

MATERIAL AND FLYING FRAGMENTS, ENĆ

DANGERING OPERATING PERSONNEL.

3.7 Overspeed - The DĆC motor is performance rated

to develop nameplate horsepower when operated at

rated base speed. The base speed of the DĆC motor is

defined as the speed at which the motor will operate

when excited with rated armature terminal voltage,

rated shunt field. current and when coupled to a driven

load requiring rated torque. The actual speed at which

the motor will run under these conditions will fall within

a range of +7.5% from nameplate base speed. Typical

base speeds for industrial DC machines include 650,

850, 1150, 1750 and 2500 RPM.
Many DĆC machines are also performance rated to opĆ

erate above base speed in a constant horsepower" or

field weakened" mode. These DĆC machines may be

incorporated into adjustable speed drive systems

which allow controlled reduction in shunt field current

while maintaining rated armature terminal voltage.

When so operated most of these motors will deliver it's

rated horsepower at any speed between base speed

and the indicated maximum field weakened speed. A

DĆC machine with an 1150 RPMbase speed and the caĆ

pability to be operated to 1950 RPMin a field weakened

mode will be nameplated 1150/1950 RPM.
Although rarely encountered, a single component failure

may occur within the drive controller that can apply arĆ

mature voltages in excess of 100% rated armature voltĆ

age to the motor, causing the motor speed to significantĆ

ly exceed either base speed or rated field weakened

speed. Under these conditions, motor speed may be unĆ

responsive to the operators speed potentiometer and/or

other speed references. Should such a condition occur,

the drive must be quickly stopped using the appropriate

stop" pushbutton, and the fault condition located and

corrected before returning the drive to operation.
During such a condition, the DĆC motor, associated driĆ

vetrain equipment, driven machinery and the driven

process itself may be subjected to operating speeds

well in excess of normal rated speeds. As such, the folĆ

lowing considerations are necessary:
All Reliance Electric Drive packages manufactured after

February 1,1982 (where the motor and controller are

both manufactured by Reliance Electric and furnished

together on the same Reliance Sales Order) have a maxiĆ

mum safe speed (M.S.S.) in excess of the speed that

would occur under the single point failure discussed

above or are equipped with a speed limiting device

such as tachometer loss and overspeed protection,

armature voltage relays or a motor overspeed switch.

(Assuming the drive equipment is operated on three

phase power supplies listed below.)

Rated

Armature

Voltage

Rated AĆC

Line

Voltage

Maximum AĆC

Line

Voltage

240 volts DĆC

500 volts DĆC

600 volts DĆC

230 volts DĆC

460 volts DĆC

550 volts DĆC

253 volts AĆC

506 volts AĆC

605 volts AĆC

If the above AĆC and DĆC voltage conditions are not apĆ

plicable to the installation in question. then it becomes

the responsibility of the user to calculate attainable moĆ

tor speed under the single component failure condition

using the procedure outlined below and to verify that

this speed does not exceed the M.S.S. of the motor.

CHART I

VAC

= Nominal RMS lineĆtoĆline voltage

= Base speed at full field and rated armature

voltage

Eg (NL) = Armature voltage no load
MSS = Max safe operating speed

VAC

MAX

= 1.49 x Eg (NL) x S

The motor Maximum Safe Speed, which varies as a

function of motor frame diameter, are listed below. ExĆ

amination of the motor nameplate may indicate a

M.S.S. slightly different for that specific machine. In that

case, motor nameplate M.S.S. takes precedence.

Reliance

Motor

Frame

Size

Maximum

Operating

Speed,

RPM

Reliance

Motor

Frame

Size

Maximum

Operating

Speed,

RPM

B160

B180ATZ

B210ATZ

B250ATZ

B280ATZ

B320ATZ

B360ATZ

5500

5000 5200

5000

4500

3600

3400

B400ATZ

B500ATZ

B580ATZ

B680ATZ

B840ATZ

B960ATZ

B1200

B1400

B1600

2760

2650

2475

2100

1720

1600

1440

1200

CAUTION: Motor frames not listed in the above tabĆ

ulation, or motors manufactured by others, may not

operate within their maximum safe speeds, when a

single point failure occurs. In these cases, it beĆ

comes the responsibility of the user to verify the moĆ

tor maximum safe operating speed and confirm

(using the procedure above) that attainable motor

speed under a single point fault condition falls beĆ

low the maximum safe operating speed.