DE1033765B - Arrangement for short-circuit protection with mechanical inverters - Google Patents

Description

The invention relates to a mechanical inverter, in particular for the emergency power supply. The aim of the invention is to prevent short circuits or otherwise caused overcurrents in the circuit To master the inverter. Fuses or overcurrent switches are normally used as short-circuit protection used with magnetic and / or thermal releases that are sized so that they Delayed in the event of overload, but due to the normally occurring short-circuit current in the event of a short circuit trigger instantly. In the case of an inverter of the type mentioned in the event of a malfunction flowing short-circuit currents are now generally so low that with the protective devices mentioned in the usual arrangement an instantaneous shutdown and thus a faultless one Short-circuit protection cannot be achieved.

An arrangement for short-circuit protection in mechanical inverters, in particular for emergency power supply, proposed, which is characterized in that one for in the direct current circuit A fuse designed for a lower current than the nominal current of the inverter is provided, depending on someone sensitive to spam Relay is bridged. In a further development of the invention is in series with the bridgeable A limiting resistor is provided for fuse. The measures of the invention enable the Inverters ensure that short circuits are safely controlled, regardless of the causes are. This significantly improves the inverter technology.

The invention and its significance will be explained in more detail with reference to the drawing. 1 with an inverter is indicated schematically, which can be of any type (chopper, pendulum inverter, etc.). However, the use of a liquid jet inverter is preferably considered. This consists of a centrifuge rotating in a vessel, which sprays contact jets against contacts suspended in a wreath. The inverter feeds the AC voltage poles 4.5 from a DC voltage source 2 via the inverter output transformer 3. A switch 7 closes the armature circuit of the motor. A switch 8 connects the inverter to the direct current source. A voltage-sensitive relay 9, which is preceded by an auxiliary contact 10 of the switch 8, controls a normally open contact 11. This contact 11 bridges a fuse element 12 of any type, which can also be preceded by a resistor 13. If the arrangement for short circuit protection
with mechanical inverters

Applicant:

LICENTIA Patent-Verwaltungs-G.m.b.H., Hamburg 36, Hohe Bleichen 22

Dipl.-Ing. Fritz Germann, Belecke / Möhne,

and Dipl.-Ing. Karl Brehm, Berlin-Lankwitz,

have been named as inventors

The arrangement shown for the emergency power supply is intended to be the consumer that normally is on the local network, switched to the AC voltage poles 4 by a switching device in the event of a power failure.

If the inverter is now switched on, for example because the local grid has failed, first closes switch 7 and starts the motor. In addition, switch 8 closes and sets the inverter via the fuse 12 to voltage. The resistor 13 can still be provided with ropes, to limit the inrush current. This is a further advantage of the invention because it enables contact to be established can take place in the contact device before the motor has reached its rated speed. High magnetizing currents are not to be feared.

The contact 11 closes and bridges the fuse 12 as soon as the relay 9 picks up, which is via the Contact 10 is connected to the output voltage of the inverter.

If a short circuit now occurs, regardless of where, the voltage for the Relay 9 collapse, and contact 11 is opened. So that the fuse 12 is in the circuit switched on. According to the invention, the fuse is now for a lower current than the rated current of the inverter, for example for a fifth, dimensioned, but in such a way that they can be used for short-term starting is not triggered. The short-circuit current is caused by the resistor 13 provided, for example already limited, the rated current of the fuse can be reduced accordingly. The short circuit current is now, even if it is relatively low

809 560/356

is a multiple of the rated current of the fuse 12, so that it responds without delay and the device turns off. If the short-circuit current itself or the short-circuit current limited by the resistor 13, for example is only three times the rated current of the inverter, the fuse in it will Case loaded with fifteen times its rated current and trip very quickly while the main fuse 14, which must be dimensioned for the nominal inverter current, could only respond with a delay.

For an inverter of the type mentioned, a extremely effective, general short-circuit protection can be achieved, since it does not matter whether the short-circuit occurs occurs on the consumer side or at any point within the device.

Claims (2)

Patent claims: 1. Arrangement for short-circuit protection in mechanical inverters, especially for emergency power supply, characterized in that one for a lower current in the direct current circuit designed as the rated current of the inverter fuse is provided, which depends on a voltage sensitive relay is bridged. 2. Arrangement according to claim 1, characterized in that in series with the bridgeable Fuse is a limiting resistor. Considered publications:
Titze: Faults and fault protection in electrical three-phase systems, Vienna 1953, p. 210. 1 sheet of drawings © 809 560/356 7.58