DE1002460B - Circuit arrangement for monitoring AC voltages for voltage failure - Google Patents

Description

Relays are generally used to monitor AC voltages for voltage failure, the voltage required for actuation via a Grätz dry rectifier circuit AC voltage network is taken. If the network fails 5, this relay drops out and works through his own contact any switching action.

So are z. B. circuit arrangements are known in which an accumulator battery via a to the Lighting network connected transformer and a dry rectifier with a fixed small Current is continuously charged. In parallel with the primary winding or secondary winding of the transformer there is a relay that drops out when there is no mains voltage and a break contact switches on an emergency lighting lamp to the accumulator battery.

Furthermore, circuit arrangements are known, in particular for telecommunication systems fed with alternating current, in which a switchover occurs in the event of a power failure and the resulting drop in the monitoring relay the AC supply takes place on the battery supply.

All these known arrangements have the disadvantage that if the network or the failure AC voltage creates a damping circuit for the monitoring relay, which sets the release time of this Relay enlarged considerably.

In some monitoring devices, especially in telephony, this delay is the release time of the monitoring relay is undesirable.

The invention relates to a circuit arrangement for monitoring alternating voltages for voltage failure with the aid of a dry rectifier bridge fed by the voltage to be monitored, a monitoring relay is connected to their DC terminals. At this the drop-out delay of the monitoring relay is avoided, so that any switching action can be carried out in the event of a power failure can be carried out without significant delay. According to the invention, this is thereby achieved achieves that a glow lamp is placed in series with the monitoring relay. The series scarf A relay with a glow lamp for monitoring the failure of an alternating voltage is on known. However, this arrangement can achieve the object on which the present invention is based do not loosen, as the series connection of relay and glow lamp is fed by alternating current and the relay has a dropout delay to avoid dropping when the alternating current crosses zero having. The monitoring circuit in the event of a network failure

of alternating voltages

on power failure

Applicant:

Standard Elektrik Aktiengesellschaft,

Stuttgart-Zuffenhausen,

Hellmuth-Hirth-Str. 42

Fritz Schmidt and Heinz Cordes,

Stuttgart-Zuffenhausen,
have been named as inventors

The energy stored in the relay coil is obtained by maintaining the voltage on the glow lamp up too low current values are quickly consumed, whereby the fast release time of the monitoring relay is achieved. The choice of the monitoring relay in terms of its release time is through determines the ratio of peak current during operation to the static response current of the monitoring relay.

The invention is explained in more detail below using an exemplary embodiment according to the figures.

1 shows the circuit arrangement for monitoring an alternating voltage according to the invention;

Fig. 2 shows the current timing diagram for the monitoring relay.

In FIG. 1, the monitoring relay U is located in the secondary circuit of a transformer Tr supplying the alternating voltage via a Grätz rectifier circuit, and with it a glow lamp Eq. When the alternating voltage is present, the relay Ü is picked up and the glow lamp Gl ignited. In the event of a power failure, the relay coil transfers all of its energy to the glow lamp to maintain the discharge. According to the current-voltage characteristic of the glow lamp, the voltage remains at a high value up to very small currents. This causes a rapid drop in the current flowing through the relay coil and thus a rapid drop in the monitoring relay. In the absence of this glow lamp, the relay Ü would experience a drop-out delay in the event of a power failure, since the in

'609 770/179

the secondary winding of the transformer and located in the winding of the relay Ü magnetic energy would result in a damped oscillation about the relay Ü. A rectified half-wave current flows through the relay Ü through the Grätz rectifier circuit.

In the current time diagram shown in FIG. 2, two rectified half-wave currents with different peak currents are shown. During the time in which the current falls below the value of the static waste current until its value has again reached the static response current - denoted by ms in FIG. 2 - the monitoring relay must not drop out. From 'Fig. 2 it can be seen that this time is the shorter, the greater the ratio of peak current to static response current. This time must be made as short as possible so that a relay with a short release time can be used. The release time of the monitoring relay can thus be determined by selecting the ratio of peak current during operation to the static response current.

Claims (2)

PATENTED KITCHEN: 1. Circuit arrangement for monitoring AC voltages for power failure with With the help of a dry rectifier bridge fed by the voltage to be monitored, on whose DC terminals a monitoring relay is connected, characterized in that in There is a glow lamp in series with the monitoring relay. 2. Circuit arrangement according to claim 1, characterized in that for setting the Drop-out time of the monitoring relay the ratio of peak current during operation to static on ■ voice power. is changeable. . Considered publications:
German patent specifications No. 692 072, 695 020. 1 sheet of drawings © 609 770/179 2.57