Starters for synchronous and asynchronous motors

Our program covers three different starter systems for electric motors.

> Electronic soft starter with thyristors up to 4 MVA motor output
> Starting transformers for synchronous an asynchronous motors up to 25 MW
> Liquid starters

Our electronic soft starter protects your motors and the driven machine by way of a soft acceleration control. It avoids the typical starting problems like high currents and high wear and tear. These products are available for line voltages of 400, 500 and 690V up to 3000A. The soft starters are mounted into the motor feeders. Typical applications are all non speed-controlled drives as conveyors, compressors, coolers and mixers, fans, mills, pumps and centrifuges.

The starting devices with starting transformers for medium voltages up to 13,8 kV are designed according to the three breaker method of Korndorfer. The supply covers a complete unit with transformer, vacuum breakers (star point and bridging contactors) plus protections.

Single line for starting transformers

Our starters will be supplied independently from the manufacturers of motor and switchgear. They can be mounted directly next to the motor or in a switch cabinet. The transformers can be supplied optionally with oil cooling or as dry type. For the dimensioning we need a speed / torque curve, motor starting current at direct on line operation and the WD2 values of the drive. If desired, we can dimension economic liquid starters for your plant.


Converters for DC motors

We supply digitally controlled CD converters for drives in one- and four quadrant operation, for other supply and filed excitation control with constant output in this range if desired. The field weakening reduces the torque with increased speed.

output range: 100 KW bis 12 MW
speed range: 0 bis 100%
execution: air or water
  6-, 12- and 24-pulses


DC drive with thyristors, single line and torque/speed range


This classic DC drive technique is frequently still in use. It is applied often in modernizing and revamping jobs in the steel industry. In case AEG products like Minisemi, Midisemi and Maxisemi cannot be supplied any more, we can offer suitable substitutes. The following picture shows a switch cubicle of a large rotor converter of 750V DC and 14000 Amps DC in 24-pulse execution.


This converter drives a DC rolling mill with 5150 kW at a speed of 40/80 rpm with a rated current of 750 Amp The converter for the field supply is fitted into a seperate 600mm cubicle.


Inverter for AC motors in low and medium voltage

We design and offer all necessary inverters for new plants and revampings.

VSI invertors for 2-quadrant drives (DFE):

output range: 690V to 3,5 MVA
to 2,3 kV: 1,4 to 12 MVA
to 3,3 kV: 6 to 22 MVA
to 4,2 kV: 6 to 28 MVA
to 6,6 kV: to 13,5 MW
to 10 kV: on demand
speed range: 0 to 100 %
cooling: air or water


In case AEG products like Monoverter, Semiverter, Multiverter and BL Motor cannot be supplied any more, we can offer suitable substitutes.


VSI invertors with constant voltage intermediate circuits with IGBT feeders for 4- quadrant (AFE) drives without line reactions:

Diagram for inverter free of line reactions

690V VSI with Active Front End

Current and voltage sine wave free of line reaction at the point of supply


For multimotor drives a VSI invertor can be equipped with various motor inverters and a controlled DC bus provided. From the supplying grid only the total of active power is drawn in this case. In plants frequently only some motors are operating motorically, others are feeders. The feeding drives (which are braking) across the DC bus are supplying energy to the driving motors. This is an optimal energy concept.

output range up to 690 V: 100 KVA to 4 MVA
to 2,3 kV: 1,4 to 12 MVA
to 3,3 kV: 6 to 22 MVA
to 4,2 kV: 6 to 28 MVA
speed range: 100% to 100 %
cooling: air or water cooling



VSI invertors with constant voltage intermediate circuits with IGBT feeders (AFE) and energy interchange across the DC bus for four controlled motors


BL-Motor- Inverter with constant current intermediate circuits for synchronous motors

The BL-drive is specially suitable for large driven units with only one direction, e.g. pumps, fans and compressors. It is also in use as starting inverter in power stations.


output range: approx. 1 to 50 MW
speed range: up to max 6000 rpm
cooling: air or water


Further information on the BL drive system is available as pdf-document.


Modernizing and backfitting

We avail of special experience in modernizing drives in the following fields:

> Revamping of inverters for speed controls of pumps and fans for economizing energy and reduction of losses in power stations and other industrial plants
> Modernizing of DC drives in steel plants or mines

The following picture shows the mounting of a water cooled inverter in a container cubicle and its installation in a machine hall of a power station in Italy. It was an order for four feed water pumps with 2,1 MW each in a container of 5 by 3 by 3 meters with a complete inverter and insulated direct water cooling for each drive.


Containerized unit for an inverter driving a water feeding pump


Simplified transport of a containerized unit

We will modernize not only AEG thyristorised equipment, but also existing products of other makers from east or west Europe and include usable parts into new solutions. There is often considerable economic interest in modernizing old DC drives of medium or large output. It is often the case in in rolling mills, cement plants, mine hoists and cranes. The new, fully digital information technology may also be used for drives of high dynamic requirements. Existing DC motors will be inspected in case of need and refurbished. Our suppliers can provide for new motors if required.

In case of modernization of thyristor equipment sometimes it is useful to retain the old thyristor power modules. We can supply in such cases a new digital control with an interface made to order which suits the given situation of the power module. The new control can be fitted to usual bus systems (Profibus-DP, CAN) in order to communicate with the corresponding automation level. The control electronic has a drive structure which may be flexibly combinable with a number of technological control units, automatic control circuits or failure memories. If new power modules are required, we are prepared to offer them.

Drives and thyristorized equipment with highly dynamic properties

Especially for test benches of the automobile industry we can offer suitable speed controlled drives. Our offer includes the semiconductor equipment, motors with rotors of low rotating masses and intelligent interfaces for primary automation modules. We avail of considerable experience with motor and gearbox test benches as well as car test benches and for other related uses.


Test benches for cars loaded with dynamic inverter


Gearbox test bench with IGBT drives


> Output range 10 to 4000kW
> Feeder 400 to 690V
> Line frequency 50 or 60 cycles
> Line re-feeder by pulses
> Torque control reaction time < 1,5ms
> Speed control range with speedometer 1:1000
> High synchronism at low rpm
> Field control > 1:5
> Refrigeration by air or water
> Protection type IP23 und IP54
> EMV acc. to IEC 801-2...4


Other applications upon request.


Diagram of torque and intermediate circuit voltage after an increment of the reference value of -50% to +100%


Drives for conveyor belts

The advantages of a conveyor belt with speed control:

> Instead of slipring motors, squirrel cage motors should be used
> The resistance controller in the rotor circuit may be omitted
> A complete reserve drive for revision purposes can be omitted
> A lower, more economic belt configuration can be selected
> The losses are considerably lower
> The maintenance cost can be reduced, lesser failure and breakdown times
> Roller, belt and gear are subject to lower wear rate

If existing conveyor belts are equipped with speed controls and the slipring motor shall be retained, we can offer an electronic speed control with a subsynchronous thyristorized cascade (USK).



Conveyor in a salt mine with inverter drives of 3x200kW for 1600 tons per hour


6 kV energy supply with transformer, switch board and inverter on a transport rack

An essay on the above mentioned plant with three phase squirrel cage motors regulated by speed controlled inverters is available as pdf.