Rockwell Automation WebPak 3000 DC Drive Application Workbook Version 1.1 User Manual
Page 17
Configuring the Speed Loop
3-7
ABOUT SPEED PARAMETERS
It is important to understand the relationship of the following speed-defined parameters:
TOP
LINE
SPEED
(P.020) is the maximum speed of the drive in length per time; for example,
feet per minute.
GEAR
IN
SPEED
(P.011) is the motor speed in RPM that results in
TOP
LINE
SPEED
(P.020). If the
section is a center-driven unwind or winder (variable diameter),
GEAR
IN
SPEED
is the motor
RPM that results in
TOP
LINE
SPEED
at
EMPTY
CORE
DIAMETER
(P.830).
MAXIMUM
SPEED
(P.004) is the maximum motor speed in RPM that can be supported by the
connected load.
Example 1
Typically,
TOP
LINE
SPEED
(P.020),
GEAR
IN
SPEED
(P.011), and
MAXIMUM
SPEED
(P.004)
correspond to the same operating speed. However, due to mechanical or process limits,
MAXIMUM
SPEED
(P.004) may be less than
GEAR
IN
SPEED
(P.011).
Assume the following machine specifications:
Line speed = 2000 FPM
Motor = 10 HP, 500/2000 RPM
Empty Core = 4 inches
Full Roll = 24 inches
Motor is direct-coupled to roll (1:1 gear ratio)
Under these drive conditions, the speed parameters would use the following settings:
TOP
LINE
SPEED
(P.020) = 2000
FPM
GEAR
IN
SPEED
(P.011) = 1910
RPM
P.011 = 2000
FPM
x 12 inches = 1910
RPM
(4 x
π
)
inches/rev
MAXIMUM
SPEED
(P.004) = 1910
RPM
Example 2
Assume the following machine specifications:
Line Speed = 2000 FPM
Motor = 10 HP, 500/2000 RPM
Empty Core = 3 inches
Full Roll = 24 inches
Motor is direct-coupled to roll (1:1 gear ratio).
Since the 3-inch core will be required to operate at 2546 RPM when the line speed is set at
2000 FPM, it will be necessary to limit maximum line speed to 1571 FPM at the 3-inch core
diameter so that the maximum motor speed of 2000 RPM is not exceeded. This is an
inherent feature of the drive reference design.
The maximum line speed of 2000 FPM will be attainable when the roll diameter builds up to
3.82 inches.
Under these drive conditions, the speed parameters would use the following settings:
TOP
LINE
SPEED
(P.020) = 2000 FPM
MAXIMUM
SPEED
(P.004) = 2000 RPM
GEAR
IN
SPEED
(P.011) = 2546 RPM
!
ATTENTION:
The drive’s overspeed protection is based on
GEAR
IN
SPEED
(P.011).
GEAR
IN
SPEED
is typically set at or below the motor’s rated base speed
or field weakened speed. If the application requires
GEAR
IN
SPEED
to be set
above motor base speed (fixed field) or above the motor’s nameplate field
weakened speed, the drive’s internal motor overspeed fault protection is not valid.
In this case, the user is responsible for providing external overspeed protection,
such as a motor overspeed switch. Failure to observe this precaution could result
in severe bodily injury or loss of life.