Four quadrant control of DC Motors
Model 2746
Isolated analog or digital inputs
Model 2747
External potentiometer


• Full wave unidirectional DC output up to 2 HP
• Opto-isolated motor speed input
• Opto-isolated motor inhibit input
• Dip switch setting for horsepower selection
• Acceleration/deceleration adjustments
• Maximum/minimum speed, torque and regulation controls
• Quick removable barrier block connections


MODEL 2746–2747 motor controls are exceptionally rugged, full wave, unidirectional (single quadrant) units that control motor speed and torque of shunt wound and permanent magnet DC motors. These two models are equivalent except that Model 2746 has an isolated speed command input, while Model 2747 uses an external 5KO speed potentiometer.

Both models are fully adjustable, industrial grade controls packaged in compact, low cost frames which make them ideal for OEM applications that require unidirectional control with isolated or remote speed command inputs.

These controls are designed to be easily interfaced to either analog or digital low level circuitry, and input signals are isolated from motor and power line with 1500 VDC minimum isolation voltage, reducing the possibility of grounding, noise or safety problems.

ANALOG INPUTS: Motor speed is proportional to the amplitude of the isolated input signal (see figure). The equivalent circuit of the isolated speed input port is 150O in series with diode voltage drop of 1.1 VDC. The input/output curve is approximately linear, with a threshold at 1.3 VDC. This characteristic is suitable for precise speed control within a closed loop system where speed is sensed and and controlled externally, or for application requiring isolation at low cost without high input/output precision.

DIGITAL INPUTS: The input port may be pulsewidth modulated with 1–100 kHz TTL level signal to control motor speed. Input pulsewidth vs. motor voltage is linear, and more repeatable in digital mode than analog mode.

An isolated inhibit signal is provided. The motor operates normally when this signal is de-energized. When energized, the motor output is inhibited. The equivalent circuit of the inhibit input is 1000O in series with a diode voltage drop of 1.1 VDC.

Adjustment controls include minimum speed, maximum speed, current/torque limit, IR compensation (for adjustment of speed regulation), acceleration and deceleration. Full load rated horsepower ranging from 1/30th to 2 HP is user settable by easily accessed dip switches.

These units incorporate thyristor phase angle control and operate from nominal 115 or 230 VAC, 50/60 Hz lines. When used with a 115 VAC line, 90 VDC motors are driven. A field voltage supply producing either 50 or 100 VDC is incorporated for shunt field motors (100 and 200 VDC for 230 VAC inputs).

These POWR UPS motor controls are of high quality open frame construction, and mounting holes are provided for either bottom or edge mounting. A removable barrier block is used for input and output connections, allowing rapid field rewiring.

An optional perforated metal cover (2746 COVER) is also available.