AC-current generators for magnetic tripping tests

Flexible and reliable

The generators of the DPWM-series are assembled in a modular concept. Each module is able to generate up to 6kVA peak value. The voltage and current outputs can be modified for different applications.


An example will show:

A 1500 A generator can be used in the range from 1 to 50A with 150V eff. open source voltage, which is done by one module. This maximal tripping voltage can be adjusted by software. At currents above 50A this maximum voltage will be limited to 20V eff. Depending on the needed current one module after the other will be added to the output. Finally at 1500 A there are 5 modules activated.

The activation of each module is done by an optical bus. This bus system is controlled by a signalprocessing unit. The current output of each module is switched by semiconductors without any contactors. So there is no wearing or noise. The switching between those configurations is done at the zero crossing point, without any disturbance of the output signal.

The pulse frequency is at about 250 kHz at low power. With increasing power the pulse duration increases and the frequency decreases. The efficiency is at about 89 to 96 % depending on the operating point.

For magnetic tripping tests there are individual current cycles programmed. So it is possible to run 100ms holding current (at this current the device should not trip) followed by a programmable break (i.e.20ms) and finally the tripping current with another 100ms impluse time. If the device trips (like it should) at this tripping current, the time result is shown at the display and can be transmitted by serial/TCP interface.

But even more complex cycles like scanning functions are possible. With several steps (10 steps for example) starting from a lower level increasing by equal steps the tripping value can be scanned. The impulse is normally between 40ms and 60ms per step. With break times of 20ms this test needs less than 1 second and shows the real tripping value.

 

The range of this kind of generator type is actually from about 200A up to 5000A. It would be possible to provide even bigger generators.

Normally we built this kind of generator in an alu-profile housing with wheels. Standard sizes are 650 x 650 mm basic area with variable height of 1000mm up to 1800mm. But it can even be reduced down to 800mm to fit under transporting belt systems if necessary.

An example of price:
A generator with current range from 1 to 900A with a short time power of 15kVA would cost about € 22.000 to € 25.000