Ziehl-Abegg SE (Germany) – by Ralf Heusser, Ziehl-Abegg Product Manager and senior electronics engineer.

Contactor-less frequency inverters are now state-of-the-art technology in the elevator industry. The silent operation of the elevator machine is valued by owners and operators of elevator systems. But what about the operation of the motor brake?

Modern frequency inverters are fitted with the Safe Torque Off (STO) function, dispensing with the need for motor contactors. This allows the operation of the elevator machine quietly without contactors, enabling the frequency inverter to be installed in the elevator shaft, except in extremely dusty environments such as in power plants or the cement industry.

However, eliminating the motor contactors puts the focus on a different noise: the noise of the switching action of brake contactors is becoming an ever-increasing nuisance. People in neighbouring rooms as well as the elevator passengers themselves are increasingly complaining about this annoying level of noise.

Certified solution:
Ziehl-Abegg has taken this problem on board and developed the ZAsbc4C electronic brake control.



The ZAsbc4C replaces the contactors, which are a compulsory requirement for the traditional brake control on the elevator drive, with an electrical safety device (safety circuit) containing electronic components in accordance with EN 81-20.

All the negative features of the conventional brake control are therefore now a thing of the past:

• annoying switching noises produced by the contactors
• EMC malfunctions caused by the switching action of the contactors
• Faults in the elevator unit caused by malfunctioning contactors

The TÜV Rheinland conducted a type examination test of the ZAsbc4C on the basis of the Lift Directive 2014/33/EU.

Which brakes – which functions?
The ZAsbc4C is used for brakes with and without over-excitation, whether on a synchronous or asynchronous machines. An additional safety brake can also be used on elevator machines with gearbox.

The ZAsbc4C can be set to the existing brake type on the construction site. This prevents the problem of a mismatch between electronic control and brake type (over-excited or not), avoiding the need for costly replacements and delays on the construction site.

The brake control has separate inputs for the tests which have to be conducted on the brakes, due to this both outputs for the brake circuits can be activated separately from each other. If the elevator system has an uninterruptible power supply to cope with a power failure outage, the brakes can be released via the ZAsbc4C for an emergency rescue.

The inputs on the electronic brake control enable these functions to be activated via external switches or push -buttons e.g. in the elevator control panel. This is a great advantage particularly if the location of the ZAsbc4C and frequency inverter in the elevator shaft is difficult to access.

Drive control and frequency inverter – the perfect combination:
The ZAsbc4C not only contains the electronic brake control. There are integrated relays available for activating the Safe Torque Off (STO) safety function on the frequency inverter. If the end of the safety chain is connected on the ZAsbc4C, the safe stop of the frequency inverter is carried out by these relays. In case of an interruption of the safety chain the STO safety function will be activated and the power to the elevator machine will be disconnected.

The ZAsbc4C is pre-assembled in the factory with connecting cables to provide this perfect synchronisation with the ZAdyn4C frequency inverter from Ziehl-Abegg. The ZAsbc4C is mounted to the ZAdyn4C with a bracket and the control cables are simply connected. This means simple and fast installation on site – with retrofitting option at any time. This decentralisation of the brake control means the size of the switch cabinet can be reduced further.

Quiet and standard-compliant:
The electronic brake control ZAsbc4C and ZAdyn4C contactor-less frequency inverter is the perfect package for fast installation combined with quiet and low-maintenance operation of the elevator machine, including the brakes. Both components meet the requirements of EN 81-20.

About Ziehl-Abegg:
Ziehl-Abegg (Kuenzelsau, Baden-Wurttemberg, Germany) is one of the leading global companies in the ventilation and drive technology sector with matching control technology. Examples of application areas for the products include heating and refrigeration plant, clean rooms and agricultural systems. Back in the Fifties’ Ziehl-Abegg established the basis for modern fan drives: external rotor motors which remain, even today, state-of-the-art worldwide. Another area of business is electric motors which provide the power e.g. for elevators, medical applications (computer tomography equipment) or deep-sea underwater vehicles. The theme of electro-mobility/clean power for motor vehicles was established as part of the Ziehl-Abegg Automotive Team in 2012 that incorporates the sales and further development of a wheel hub drive for urban buses already in use in several countries

The high-tech company has an impressive innovation power. Ziehl-Abegg employs 1,950 personnel in its production plants in Southern Germany. The company has a global workforce of 3,450, spread between 16 production plants, 27 companies and 97 sales locations. The products, approx. 30,000 in all, are sold in more than 100 countries. Sales revenues in 2015 totalled 448 million euro. Exports account for two thirds of sales.

Emil Ziehl founded the company in Berlin in 1910, manufacturing electric motors. After the Second World War the company’s headquarters were relocated to Southern Germany. Ziehl-Abegg SE is not a listed company but family-owned.