Technology

Functional Safety

The Safe Torque Off capability of Copley's PLUS Panel drives eliminates the expensive contactors and complex wiring traditionally used in safety critical applications. Safe Torque Off provides two drive enable inputs facilitating system conformance to SIL 3 (IEC 61800-5-2) & Category 4 PLe (ISO 13849-1).

Field Oriented Control

Field oriented control is a motor commutation scheme which enables brushless motors to run faster and cooler. This is made possible by maintaining optimal orientation of the rotating magnetic field and permanent magnets at all speeds.

 

In a traditional control scheme, the commanded current is modulated by sinusoidal waveforms to create a rotating magnetic field in the motor stator. The frequency of the sinusoids is speed dependent. At higher speeds, current phase lag occurs causing misalignment of the magnetic fields. This causes motor heating and limits speed.

Precision Positioning

In low friction systems (air-bearing linear motors and voice-coil motors), the amplifier drives small positive and negative currents to maintain zero error when holding position. Amplifier crossover distortion now becomes a factor as non-linearities around zero current can compromise precision.

 

Copley amplifiers employ two techniques to eliminate crossover distortion in analog amplifers: carrier cancellation - an optimal solution for brushless motors, 50% modulation - typically used for voice coil motors.

 

 

Edge Filtering

A PWM amplifier generates switching transients that can couple into other sensitive circuits. Although careful attention to shielding and grounding can eliminate many problems, Copley Controls offers optional Edge Filters to limit

the generation of transient noise.