I. INTRODUCTION
The KBWM™ Vari-Drive™ adjustable speed SCR control for DC motors offers proven relia-
bility in a rugged all-metal NEMA-1 / IP20 enclosure. The Vari-Drives™ are equipped with the
ultimate KBMM™ speed control module. They are specifically designed for fractional horse-
power permanent magnet (PM) DC motors. Two models are offered. The KBWM-120 is
designed for 115 VAC input and is rated 1/100-1/3 HP at 90 VDC. The KBWM-240 is
designed for 208/230 VAC input and is rated 1/50 – 3/4 HP @ 180 VDC.
Note: Model
KBWM-240 can also be used on 90 Volt DC motors. See Section IID, on page 6.
KB’s exclusive Plug-in Horsepower Resistor®* automatically presets the drive’s IR Comp. for
maximum performance and CL circuits for safe operation on various motors. Although fac-
tory calibrated, internal trimpots for MIN, MAX, IR, CL, ACCEL and DECEL can be used to
fine-tune the KBWM™ for specific applications. Connections to the control are via a barrier
terminal block. By changing the orientation of the front cover, the wiring can be brought in
either from the bottom or the top of the control.
Motor failure due to demagnetization is eliminated by the patented ultra-fast Direct-Fed™
current limit circuit. The controls contain AC line and armature* fusing, which provide pro-
tection against catastrophic failure. Auto-Inhibit®, a KB exclusive, allows the drive to be
turned on and off rapidly using the AC line without damage to the control and/or motor. The
internal CL LED is a diagnostic indicator that lights when the motor is overloaded.
A conveniently located front panel lighted rocker switch controls AC line input power to the drive.
*Plug-in Horsepower Resistor® and armature fuse supplied separately.
2
This product complies with all CE directives pertinent at the time of manufacture. Contact
factory for detailed installation and Declaration of Conformity. Installation of a CE approved
RFI filter (KBRF-200A [P/N 9945C] or equivalent) is required. Additional shielded motor cable and/or
AC line cables may be required along with a signal isolator (KBSI-240D [P/N 9431] or equivalent).
Parameter Specification
Speed Range Ratio 50:1
Armature Feedback Load Regulation (0 - Full Load, 50:1 Speed Range) (% Base Speed) 1**
Control Linearity (% Speed vs. Dial Rotation) 2
Line Voltage Regulation at Full Load, ± 10% Line Variation (% Base Speed) 1/2**
CL/Torque Range (% Full Load) 0 – 200
ACCEL Time Range (0 – Full Speed) (Secs.) 0.2 – 10
DECEL Time Range (Full – 0 Speed) (Secs.) 0.2 – 10
MIN Speed Trimpot Range (% Full Speed) 0 – 30**
MAX Speed Trimpot Range (% Full Speed) 50 – 110**
IR Comp. Trimpot Range (at Specified Full Load) (Volts) 0 – 24
Maximum Allowable Ambient Temperature at Full Rating (ºC / ºF) 50/122
TABLE 1 – GENERAL PERFORMANCE SPECIFICATIONS
**Performance is for SCR rated PM motors only. Lower performance can be expected with other motor types. Factory
setting is for 3% load regulation. To obtain superior regulation, see Section VI F on page 10.
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