SCR/DC Variable Speed Motor Drives

The controller is designed to be integrated into a drive package selected and wired by the user. As such, it may be necessary to provide either a number of required operator’s controls or equivalent relay contacts.

The control functions are:

  • Speed adjust or torque control potentiometer
  • Start pushbutton switch, or relay contact
  • Stop pushbutton switch, or relay contact
  • Forward/Reverse switch


SCR/DC Variable Speed Motor Drives

The Bronco DC controller is available in a NEMA 4/12 enclosure or as an open chassis unit designed for panel mounting. The controller consists of a power converter section containing the SCR power block and other high voltage circuits and a control card mounted above the power converter.

Ratings Horsepower Range:

  • 115 V 1/4-1 HP
  • 230 V 1/2-2 HP
  • AC line input Voltage: 115 or 230 VAC ±10%
  • AC line frequency: 50/60 Hz ±2 Hz
  • 115 VAC Supply
    Armature Voltage: 0-90 VDC
    Field Voltage: 50/100 VDC
  • 230 VAC Supply
    Armature Voltage 0-180 VDC
    Field Voltage 100/200 VDC

Service Factor: 1.0
Duty: Continuous
Max Load Capacity: 150% for 1 min.
Line Protection: Fuse

Operating Conditions

Ambient Temperature:

  • Chassis Model 0-55° C
  • Enclosed Model 0-40° C

Relative Humidity: 5-95% non condensing
Altitude: to 3300 ft. (1000m)

Performance Characteristics

Speed Range:

  • 30:1 with Armature voltage Feedback
  • 50:1 with optional Tach-generator Feedback

Speed Regulation (% of motor base speed) – For 95% load change.
Armature Voltage: Feedback ±2%
Tachometer Feedback: 1/2 – 1&337;
(non-reversing models only)


Current Range: 2.5, 5, 7.5,10 Amps DC Nominal(Adjustable to 150% each range)
Max Speed: 75 – 110% of motor base speed
Min Speed: 0 – 30% of Motor Base Speed
IR Compensation: Adjustable
Acceleration: 1 – 5 Seconds (Linear, 0 to Top Speed)