Overview
The KB Electronics KBWM Vari-Drive is an adjustable speed SCR control for DC motors, offering proven reliability in a rugged all-metal NEMA 1 enclosure. It is specifically designed for fractional and sub-fractional horsepower permanent magnet (PM) DC motors, and is also suited to shunt wound motors and magnetic particle clutches.
Two models are offered. The KBWM-120 is designed for 115 VAC input and is rated 1/100 to 1/3 HP at 90 VDC. For motors rated 1/50 to 3/4 HP at 180 VDC, the KBWM-240 operates from a 230 VAC input. Both models are equipped with the KBMM speed control module at the heart of the drive.
Key Features
KB’s exclusive Plug-in Horsepower Resistor automatically presets the drive’s IR Comp and Current Limit (CL) circuits for safe operation on various motors. Although factory calibrated, internal trimpots for Min, Max, IR, CL, Accel and Decel allow the KBWM to be fine-tuned for specific applications. Connections to the control are made via a barrier terminal block, and by changing the orientation of the front cover, wiring can be brought in from either 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 control contains AC line and armature fusing, providing protection against catastrophic failure. Auto-Inhibit, a KB exclusive feature, allows the drive to be turned on and off rapidly using the AC line without damage to the control or motor. An internal CL LED is a diagnostic indicator that lights when the motor is overloaded, and a conveniently located front panel lighted rocker switch controls AC line input power to the drive.
Accessories
The KBWM requires a properly sized Plug-in Horsepower Resistor and armature fuse to be installed for the control to operate. The Plug-in Horsepower Resistor automatically calibrates the drive to the connected motor’s horsepower and armature current rating, with individual resistor part numbers available across the full motor horsepower range. An armature fuse, matched to the motor’s approximate DC current draw, is also required. CE compliance additionally requires the KBRF-200A RFI filter.
Common Applications
The KBWM Vari-Drive is used across applications requiring compact, reliable speed control of small PM, shunt wound and universal DC motors, including conveyors, mixers, small machinery, magnetic particle clutch control and other OEM equipment using fractional or sub-fractional horsepower DC motors.
Selection Considerations
Selecting between the KBWM-120 and KBWM-240 depends on your motor’s armature voltage and available AC supply: the KBWM-120 suits 90 VDC motors on a 115 VAC supply, while the KBWM-240 suits 180 VDC motors on a 230 VAC supply. Once the model is confirmed, the correct Plug-in Horsepower Resistor and armature fuse must be selected based on the motor’s horsepower and rated armature current — both must be specified for the control to operate correctly.
Motordrives Australia can help confirm the right KBWM model, Plug-in Horsepower Resistor and armature fuse based on your motor’s horsepower, armature voltage and current rating.
Support And Enquiries
Motordrives Australia supplies and supports the KB Electronics KBWM Vari-Drive for Australian machine builders and maintenance teams. For assistance with model selection, horsepower resistor matching or armature fuse selection, contact our team with your motor’s horsepower, armature voltage and current rating.
