In prin­ciple, extra-low voltage is defined as the low-voltage range with a maximum of 120 V DC or a maximum of 50 V AC. These values are not entirely harm­less to humans and animals, but are not life-threat­ening. This type of extra-low voltage in the surrounding area can be also appro­priate for sensi­tive devices when ensuring safe oper­a­tion. It cannot be stated across the board what extra-low voltage is appro­priate for elec­tric drives for safety reasons.

The drives designed to indus­trial stan­dards from ebm-papst St. Georgen, which are used in many automa­tion appli­ca­tions, are usually used with extra-low voltage – DC volt­ages of 24 or 48 V (Figure 1) to be specific. This does not always mean that the motors have to be oper­ated at precisely these volt­ages, but rather that trans­formers in the power supply units and batteries in mobile devices ensure the neces­sary elec­trical isola­tion and safety.

Modular drive system for extra-low-voltage oper­a­tion

As is usually the case with DC volt­ages below 60 V, there is gener­ally no need for complex acci­dental contact protec­tion for the drives, as the extra-low volt­ages are consid­ered safe in a normal envi­ron­ment. There is no stan­dard defi­n­i­tion for safety extra-low voltage, but the aim is for this voltage to be completely safe. Whether it is depends on the appli­ca­tion, as an indus­trial robot or a driver­less trans­port system pose different require­ments than a medical device which is used directly on the patient. An oper­ating table (Figure 2) is a good example of this because although there is no risk of life-threat­ening elec­tric shocks at less than 60 V DC, even the smallest of muscle reflexes caused by elec­tricity could have serious conse­quences for patients or surgeons. In such cases, the entire safety concept and device design deter­mine the right voltage to be chosen. The extra-low-voltage drives are a very good choice here (Figure 3).

Fig. 2: Medical tech­nology places partic­u­larly high safety require­ments. In the case of an oper­ating table, even the smallest muscle reflexes caused by elec­tricity could have fatal conse­quences for patients or surgeons. (Graphic | Adobe Stock/Viktor)

Fig. 3: ECI 80 servo drive with robust Optimax trans­mis­sion for use in oper­ating tables, for example. Thanks to the modular drive system, this drive can also be indi­vid­u­ally config­ured with encoder systems, effi­cient brakes (Green Brake), etc. (Graphic | ebm-papst)

Low voltage, a wide range of advan­tages

What does this mean for drives from ebm-papst’s modular drive system? At the heart of all possible config­u­ra­tions are elec­tron­i­cally commu­tated internal and external rotor motors in the power range of approx. 10 to 750 W, all of which work with extra-low volt­ages. In addi­tion to the motors, control elec­tronics with different commu­ni­ca­tions inter­faces, different trans­mis­sion vari­ants, and encoders and brakes are avail­able so that drive solu­tions can be imple­mented across all indus­tries.

Contrary to expec­ta­tions, extra-low voltage does not mean a reduc­tion in perfor­mance; the oppo­site is the case.  For example, elec­tri­cally commu­tated drive systems, such as in the Argo­Drive driving/steering system, drive driver­less trans­port vehi­cles (i.e. auto­mated guided vehi­cles (AGVs), Figure 4) in intral­o­gis­tics and are high-torque and effi­cient. Users do not need to make any compro­mises on perfor­mance and can still be sure that the vehi­cles pose no risk of elec­tric shock.

A typical extra-low-voltage drive from ebm-papst can usually achieve more than 3 times the perfor­mance (or even higher) of a compa­rably powerful low-voltage drive with elec­tronics and sensors, with the same instal­la­tion space and weight (Figure 5, table). Anyone who values compact design in combi­na­tion with simple instal­la­tion and commis­sioning is there­fore in the right place.

Drives for AGVs

Those who can rely on drives with extra-low voltage for their appli­ca­tion without any prob­lems, as is the case with AGVs, also benefit in unex­pected areas: for example, personnel without special qual­i­fi­ca­tions may carry out commis­sioning if this is permitted by the safety and risk assess­ment. Simpler system and factory concepts could be possible for assembly robots, for example. Using extra-low voltage there­fore pays off many times over – the right safety extra-low voltage even more so. This also includes appli­ca­tions in which a partic­u­larly high level of elec­trical safety must be guar­an­teed, such as in oper­ating tables as mentioned above, as even if manu­fac­turers have very demanding require­ments here at first glance, the right solu­tion can usually be found.

They are respon­sible for their device and define the require­ments for the drives accord­ingly. These include compli­ance with air gaps and creepage distances, insu­la­tion concepts, and the use of certain mate­rials that must not be allowed to outgas or burn, for example.

A drive for every appli­ca­tion

Thanks to ebm-papst’s decades of expe­ri­ence, a stan­dard solu­tion from the modular drive system with well over 4,000 possible combi­na­tions can usually be found in such cases. Due to the extra-low voltage, the cables for the elec­trical connec­tions can be dimen­sioned smaller. Compared to low-voltage drives, these motors and elec­tronics are there­fore much more compact and can be easily accom­mo­dated even in confined instal­la­tion condi­tions.

With the test facil­i­ties avail­able in-house at ebm-papst, the selected drive solu­tions are put through their paces and appro­priate docu­men­ta­tion is produced. Stan­dard drives can also be adapted to user require­ments with reason­able effort. A different approach can even help, as perhaps the desired effect can even be achieved with an elec­tri­cally isolated power supply unit, for example.

ebm-papst in medical tech­nology