Hybrid Servo Cables Do More For Less

If you design servo systems, you may not pay much attention to the cost of the cabling. But you should.

The upfront and lifetime costs associated with power and signal cables can represent a significant portion of the total outlay for a servo system. And the smaller the servo system, the more the cable costs matter.

Fortunately, there’s an up-and-coming control architecture that can reduce the lifetime costs of servo cabling by more than 35%.

Called HIPERFACE DSL®, this digital servo architecture uses a single hybrid servo cable for both power and signal. This cable contains a shared signal pair for the motor feedback and temperature signals, both of which are modulated for transmission. This streamlined approach to cabling eliminates the need to buy, install and maintain standalone encoder and resolver cables.

Selecting Hybrid Servo Cables

In addition to its cabling advantages, HIPERFACE DSL® offers performance benefits from a servo control standpoint, and it has already gained support from the world’s leading drive manufacturers. So you may soon find yourself in the market for a cable compatible with HIPERFACE DSL.

When you do specify these hybrid power and signal cables, keep the following design considerations in mind to minimize cost while maximizing performance:

    •       Look for a tight bend radius. Many hybrid cables will see use in cable tracks. In these applications, look for cables with a tighter bend radius, which may allow you pick smaller, more economical cable tracks.

    •       Pay attention to the cable insulation. Hybrid servo cables tend to use either PVC or —about 20% smaller for this type of cable.

polypropylene core insulation systems. Each has advantages. PVC, for example, supports a slightly higher temperature rating. But polypropylene offers much better electrical properties. These include low capacitance and a relatively low dielectric constant, which limits leakage current to the shield and screen. The superior electrical properties mean that polypropylene insulation can be substantially thinner than PVC for a given characteristic impedance level. And thinner insulation means smaller cable diameters

    •       Go for durability. Hybrid servo cables vary widely in their durability. So it’s important to evaluate the resistance to temperature extremes, oil, UV light and flame. When using servos in cable tracks, add wear resistance and maximum travel length to the list of factors to consider. In general, you should lean toward polyurethane jacketed products for use in cable tracks and in harsh environments.

Single Cable Solutions

To serve the fast-growing HIPERFACE DSL market, we have developed two new hybrid servo cables:

•   OLFLEX® SERVO FD 7DSL features a polyurethane jacket for use in cable tracks.

•   OLFLEX® SERVO 7DSL is PVC jacketed for fixed installations.

Both products meet HIPERFACE DSL standards and have UL and AWM approvals. Download the full specifications here.