DE463875C - Three-phase reduction circuit - Google Patents

Description

All hoist drives for hoists in which three-phase asynchronous motors are used are known to have the disadvantage that when lowering heavy loads with oversynchronous Speed is the lowest speed when the control unit is fully extended and increases all the more, the further the control unit is reset after the zero position. The cause this is known to be the fact that when switching back into the rotor circuit there is more resistance is placed and consequently the counter-torque that decelerates the pulling load of the engine is getting smaller and smaller.

Various means have now been used to alleviate this problem or eliminate it entirely. So one often only switches on the lowering side of the control apparatus a part of the starting resistor connected upstream when lifting in order to even on the first position to get no impermissible increase in speed. Strength However, power surges when switching on and a lack of regulation ability make this circuit unsuitable for many purposes.

The application of counter-current positions on the lowering side in front of the lowering force positions Although it allows itself to throttle the speed. Within the lowering force positions but there is still the possibility of an impermissible increase in speed.

Finally, there are circuits in which, with the help of auxiliary rollers or contactors, the Starting resistances after the respective short circuit when switching back until it is reached remain short-circuited when the control unit is in zero position. With this circuit but the ability to regulate is also severely limited, since everyone reached once Resistance short circuit is maintained until it is switched off. That makes it special unpleasantly noticeable when switching off from the short-circuit position, because during the entire switching path the motor remains constant Speed continues. Special auxiliary rollers have therefore been provided in the control apparatus through their use the aforementioned device is rendered ineffective in the case of light loads. Apart from that The driver must decide whether he is heavy on the resulting enlargement of the control device has (pulling) or light loads in front of you, before switching on the control apparatus, which is not easy in borderline cases.

Finally, there are circuits that turn off when the control unit is switched back in any position the engine is switched off immediately and stopped even before the control unit is in the zero position. In general, however, this only happens for the purpose of stopping the motor quickly when it is switched off and the switching segments to spare the control apparatus. The above-

The mentioned disadvantage of insufficient control is particularly evident in these circuits, because the direct shutdown of the engine, as I said, when switching back from all Positions done out; with lowering circuits also when lifting. And that's special undesirable.

The invention now relates to a circuit in which the disadvantages mentioned ίο be avoided by running the engine only when lowering and only under certain conditions switched off immediately after leaving the short-circuit position of the control apparatus without having to go through all resistance levels first.

In the drawing, the new circuit is shown on the basis of some exemplary embodiments. Fig. Ι shows a circuit in which the stator and rotor are switched directly by the controller, while Fig. 2 shows a contactor control in which the master roller and contactors are controlled. α is the stator, b the rotor, c the brake fan, d the starting resistor, e the controller or the master cylinder, / a centrifugal switch. In Fig. Ι are also g, h and / Sagittarius. In Fig. 2, g is a top contactor, h is the column contactor for lifting, i for lowering; k are rotor contactors. The mode of operation of the new circuit is now as follows:

When the controller e (Fig. 1) is switched on in the lowering direction, a current first goes from the controller finger /? via a, through the pull coil from contactor g to S. The contactor starts up and is held by the control finger and auxiliary contact R ₁₀ . The contactor g closes a new circuit from R through the pull coil from contactor h to S. When this contactor starts, the mains connections /? and S to the controller and the engine can now be started. The short-circuit position of the controller is now divided into positions 5 and 5 '. If the switch is only switched up to position 5, it is possible to switch back again in the usual way, with the starting resistor d being switched upstream again in stages. But if you switch through to position 5 ', contactor g is switched off. However, contactor h still holds above R ₂₀ . Only when switching back from position 5 does R ₂₀ interrupt, the contactor h switches off, the stator and the brake fan connected in parallel to it are de-energized and the brake is applied.

The mode of operation of the control is correspondingly as shown in Fig. 2. When switching on in the lowering direction, the auxiliary contactor g · is switched on again first. Then the stand contactor receives voltage via R ₁ s and 5, and the stand is switched on.

When position 5 is exceeded, contactor g drops out, but contactor i is still held by control fingers S, S ₁ . It only switches off when you go back to position 4.

The driver can therefore still decide on the basis of the observation of the falling load while driving whether he wants to maintain the control option when shifting down or not. In order to avoid an inadmissible increase in speed of heavy loads in the first positions, even if the operator is careless, a centrifugal switch / can be provided that responds when the maximum speed is reached and switches on the contactor i , which short-circuits the rotor. The last rotor contactor can of course be used for this in contactor controls according to Fig. 2.

The short-circuit position "of the controller can be designed in various ways. You can z. B. the position 5 is particularly strong, but the position 5 'at all do not rest, so that the controller is switched normally only to 5 and there is a certain Force is required to bring the shift drum to position 5 '. Or you can lock position 5 so that the guide only you have to unlock it in order to reach the go position 5 '. You have against it To always lower heavy loads, you can of course also reverse the position S simply omit, so that the immediate shutdown always takes place as soon as you click on the short-circuit position of the controller has gone.

There are also so-called rapid lowering circuits, in which the short-circuit position of the lowering side is followed by further positions in which resistance is again placed in the rotor circuit in order to achieve a faster lowering of heavy loads. The disadvantage mentioned at the beginning also occurs here. When switching back to the final control, the speed is reduced initially, but only up to the short-circuit position. When you shift down again, the speed increases again in accordance with the upstream resistance. The new device can also be connected very well with these circuits. Figs. 3 and 4 show the development of the controller for these high-speed lowering circuits, with Fig. 3 again applying to direct switching and Fig. 4 showing a master cylinder. The circuit corresponds to that shown in Fig. Ι and 2 for the rest. The lowering division 3 is the short-circuit position here. In positions 4 and 5, resistance is switched on again in the ■ rotor circuit. Now segment R _{10 can go} to position 3 - or 4, see above

that the auxiliary contactor g is switched off in position 4 or 5. At the. If the short-circuit position 3 is left after the zero position, the contactor h or i is switched off again and the motor is stopped. If only light, non-pulling loads are to be lowered, switching may only be carried out up to short-circuit position 3. The downshift then takes place again in the usual manner.

For the sake of greater security, you can also use the centrifugal switch / to here Provide for speed limitation. You can also rest on the short-circuit position, as mentioned above, train appropriately.

In the direct circuits according to Fig. 1 and 3, instead of the Schützeng · and h an auxiliary roller moved by the main switching roller of the controller can be provided, which switches off the motor in the manner described when switching back from the short-circuit position.

Claims (4)

Patent claims: i. Three-phase current reduction circuit, characterized in that that when lowering the shutdown of the motor immediately after leaving the short-circuit position of the Control apparatus takes place in the disconnection direction without first going through the starting and regulating positions of the control apparatus Need to become. 2. Three-phase lowering circuit according to claim i, in which the short-circuit position of the control apparatus is divided into two parts which are equivalent in terms of the lowering speed, characterized in that, that the immediate shutdown of the engine when switching back from the short-circuit position only occurs if the control unit has been switched to the second part of the short-circuit position. 3. three-phase current reduction circuit according to claim i, in which on the control apparatus behind the short-circuit position there are still positions in which resistances are again placed in the rotor circuit are, characterized in that the immediate shutdown of the engine when switching back from the short-circuit position only takes place when the control apparatus goes beyond the short-circuit position into a certain adjustable position Position was brought. . 4. Three-phase current lowering circuit according to claim i, 2 and 3, characterized in that that the immediate shutdown of the engine when switching back from the short-circuit position takes place by an auxiliary roller moved by the control apparatus or by contactors. 1 sheet of drawings BERUM. GKDTlUCKT IN THE