Group 31 Compact Rotary Actuators

The compact, in-line design of the Group 31 compact rotary actuator consists of an output section containing the drive train and motor, and a control module section housing the electronics. Together, these two sections provide an enclosure designed to meet NEMA 4 specifications for protection against corrosion, dust, and moisture.

The Group 31 incorporates the same type of motor used in Beck’s Group 11 and Group 14 drives. It provides millisecond response to signal commands in a modulating control loop.

General Specification

Output Torque and Timing

Model # Torque nm (lb-ft) Stroke Time (sec./90°)(50 Hz)
31-M50, 31-350, 31-250 41 (30) 29
31-M30, 31-330, 31-230 20 (15) 22

Specifications common to all models:

Drive Power 20 Vac, single-phase, 50 or 60 Hz, 0.5A, 60 Watts
Operating Conditions –40° to 65° C. (–40° to 150° F.) 0 to 99% relative humidity
Action on Loss of Power Stays in place.
Handwheel Provides manual operation without electrical power. Non-rotating during automatic operation, does not require declutching mechanism.
Motor 120 V ac, single-phase, no burnout, noncoasting. Capable of 60 starts per minute.
Gear Train Precision cut, heat-treated alloy steel and ductile iron. Self-locking and self-releasing, able to hold position at 150% rated torque.
Mechanical Stops Prevent overtravel during automatic or manual operation. Mechanical stops are external to the drive.
Drive Net Weight 25 lbs.
Max. Overhung Load 500 lbs


Cam controlled, field adjustable. Two limit switches (S3 & S4) open the motor circuit at end-of travel limits. Two auxiliary switches (S1 & S2) provied external signaling as specified through connections made at the terminal board. All four switches are SPDT and are rated for 1 amp at 120 V ac.


Precision machined aluminum alloy castings, painted with corrosion resistant polyurethane paint. All units meet NEMA 4 specifications and are also available FM approved for use in CLass 1, Div. 1, Group D; Class II, Div. 1, Groups E, F, & G; and Class III, Div.'s 1 & 2 hazardous locations.

Specifications for Control Option 3 drives (Models 31-M50 and 31-M30):

Demand Input Signal Range 4–20 mA OR 1–5 V dc
Signal Span Adjust 50% to 125% of 4 V span
Signal Zero Adjust Up to 120% of span Split Signal Range: 4-12 mA or 12-20 mA
Deadband 1% of span
Sensitivity 0.2% of span
Feedback Signal * 4–20 mA OR 1–5 V dc
Output Stability for Temperature Change +/- 0.03%/°C of Span for -40°C to 50°C
Stall Relay Contacts Form A, 10 volt-amps at 120 V ac or dc
Action on Loss of Input Signal (Power On) Stays in place or runs to any preset position (configurable).
Action on Stall Relay contacts open after 68 seconds of stall, remote signal available. Power to motor is turned off.
Handswitch Permits local operation, independent of controller signal. The handswitch is located beneath the control module cover on the control board.

Specifications for Control Option 2 drives (Models 31-350 and 31-330):

Feedback Signal * 4–20 mA OR 1–5 V dc
Output Stability for Temperature Change +/- 0.03%/°C of Span for -40°C to 50°C

* Feedback may be configured as a two wire transmitter or as a four wire active signal source. Two wire systems require a customer supplied external power supply. Four wire systems require 120 V ac supply to the drive.