The difference between a servo cable and a motor cable?

Vishaka Upreti | 10 May 2021

Electrical engineering is often concerned with motor cables as well as servo cables. But what is exactly the difference between a servo cable and a motor cable? And can I use a servo cable to connect a normal three-phase motor?

What exactly are the differences?

The fact is that both cables are designed to supply a motor with electrical energy. For this reason alone, both types of cables have a great deal in common – such as their nominal voltage of 600/1,000V.

The colour of cables and DESINA

The colour of the two cable types is the first thing you notice. While servo cables are often orange, motor cables usually have a black outer jacket.

The background here is DESINA. It is a standard intended to bring about uniformity in mechanical engineering. If a cable is manufactured according to the DESINA standard, outer jacket colour must be chosen according to cable function.

According to DESINA, motor cables have a black outer jacket. DESINA servo cables have a pastel orange outer jacket (RAL 2003).

The structure of the two cable types

Other differences are to be found in cable design. Servo cables almost always have an overall shield that is intended to prevent the propagation of electronic magnetic interference. Motor cables are used without a shield or with an overall shield.

An examination of the two cables’ cores reveals the primary differences. It is noticeable that the typical motor cable consists of the four main cores for connecting the three phases and PE. Nothing more is needed to operate a three-phase motor.

Some three-phase motors have an additional connection for a temperature sensor or a built-in brake. These are normally connected to the motor terminal board via a separate cable.

Servo motors are generally connected via a round connector. This connector has all the contacts necessary for supplying energy to the motor and for connecting temperature sensors and brakes as needed. Multiple cables cannot be fed into one of the round connectors used here. That is why servo cables have, in addition to the main cores, shielded core pairs that are provided for temperature controllers or brakes. There are servo cables without these additional pairs, but they tend to be the exception. This means that most servo cables have one or two core pairs.

Can I use a motor cable to connect servo motors?

The answer is yes. Of course it is possible to use a motor cable to connect servo motors. To do so, either the servo motor must have no connection for temperature sensors or brakes, or these connections must be designed separately. Then they can be connected via a control cable. Of course, a normal three-phase motor can be connected via a servo cable and the unneeded cores cut off.

Conclusion

The difference between a servo cable and a motor cable is primarily in design and colour. The two cable types can be connected to servo motors.

Do you need help finding the right cable for your application? We look forward to hearing from you and advising you.