RU2693835C1 - Method for starting powerful inductive load from self-contained voltage inverters - Google Patents

Abstract

FIELD: electrical equipment; mechanics.

SUBSTANCE: invention relates to methods and can be used for start-up of asynchronous AC motors. Method, which enables to perform independent cold start-up and power supply of powerful inductive load, in particular, containing asynchronous motor, from independent power sources (voltage inverters), differs by the fact that the solution is achieved by the method of resistor limitation by the specified time of the amplitude of the starting current of the load motor below the value of operation of protection of VI (UPS), but not lower than the value at which the engine can still start and unwind, and which can be used in the form of a simple circuit design with voltage inverters and uninterrupted power supplies of medium and high power.

EFFECT: technical result is provision of cold start and power supply (if necessary) from independent current sources (VI and UPS) – such household electric appliances as refrigerators, circulating pumps, powerful fans, air conditioners, et cetera, id est having above-mentioned asynchronous motor.

1 cl, 1 dwg

Description

The invention relates to methods used for starting AC induction motors, causing difficulties, and even the impossibility of their start-up and power from autonomous power sources, such as voltage inverters (IN) or uninterruptible power supplies (UPS).

Methods similar in function and purpose are carried out in numerous soft starters (SCP), using various fundamental methods and schemes in their work. For example, one of them is a phase one, the most widely known one and often used because of its moderate cost in ready-made industrial devices and technically realized by a thyristor control circuit. (Shubenko V.A., Braslavsky I.Ya. Asynchronous electric drive with phase control. M .: Energy. 1972.)

However, thyristor SCP has a significant fundamental disadvantage, in the form of a greater reduction in torque during start. The torque on the shaft of the induction motor is directly proportional to the square of the voltage applied to its windings, so if at the time of start-up a voltage U = 0.5 * Un is applied to the motor, then the torque will be M = (0.5 * 0.5) * MP = 0.25 * Mp, where Un is the nominal voltage, Mn is the starting torque of the motor when supplied with the nominal voltage. Therefore, the scope of application of the thyristor start-up mechanisms, weakly loaded at the time of start-up, for example, fans, pumps, machine drives, started in idle mode, etc. For mechanisms with a moment of resistance that varies little with speed, the use of DFD is possible at the moment of resistance Mc not more than 0.5..0.6 MP. With values of Мс = 0,6.,0,8 Мp it is possible to achieve only a partial effect of smooth start, since the starting currents in this case are not very different from the currents arising during the direct start. When the moments of resistance Mc> 0.8 Mp i. in case of severe starts, the use of thyristor SCP is ineffective. As well as in others, as well as in thyristor SCP, besides this, relatively expensive electronic components are also used, and hence, respectively, a higher price and less maintainability.

Another example of analogue in terms of its functions and purpose are the devices that implement them by the method of frequency conversion of the supply load current (patent RU No: 2422977, IPC: НРР publication date 01/14/2010) However, this method is much more complex circuitry, costly and devices operating in this way - expensive.

The objective of the invention is to provide a cold start and power (if necessary) from autonomous current sources (IN and UPS) - household electrical appliances such as refrigerators, circulation pumps, powerful fans, air conditioners, etc., i.e. part of the above asynchronous motor.

This task is achieved due to the limitation on the amplitude of the starting current of the motor below the response value of the protection IN (UPS), but not lower than the value at which the load motor can still start and unwind. To do this, we propose the following method, which consists in using to achieve the task - resistors of sufficient power and selected by the value of its electrical resistance to the required above-mentioned limitation of the starting current of the engine. At the same time, the “starter” mode of operation of the IN (UPS) batteries is also facilitated and a decrease in the voltage drop on them when the load is started is achieved.

FIG. 1 shows a functional block diagram of the method and device using it.

The enclosure of the device, encircled by a dashed contour, contains: (1) —the time relay driver (ЗРВ), (2) —the resistor unit (RB), (3) —shunt, (4, 5) —input and output. All these elements, constructively representing separate functional blocks, relative to each other can be arbitrarily located in the device case. By their inputs and outputs, they are connected by conductors to each other, according to the arrows in the above fig. 1. The device itself is located and connected in series between IN (UPS) and inductive load Rind (6) containing an asynchronous motor.

The method and apparatus operate as follows.

Output voltage IN (UPS) Uout. Inv from the input (4) through the current-limiting resistor unit (RB) (2), is fed to the load Rind (6) and at the same time is fed to the master time relay (ЗРВ) (1), which immediately starts counting the time period Trv. This time period for the ZRV is regulated and adjusted so that Tpv = Tpn, i.e. his exposure time was enough for the time Tpn sufficient spin-up of the motor load Yaind (6), and which, in turn, is governed by the selection of the resistor unit (RB).

After this time, i.e. the occurrence of the condition Trv> Tpn., the time relay (ЗРВ) is triggered by a shunt (3) it turns off the current-limiting resistor unit (RB) and itself from the power supply circuit of the load Rind (6), and to which, when its engine is already spun, the full supply voltage from IN (UPS).

This method allows to solve the technical problem of starting and powering, if necessary, any household electrical unit with an asynchronous motor from an autonomous battery power source.

Claims (1)

A method allowing autonomous cold start and power supply of a powerful inductive load, in particular, containing an asynchronous motor, from autonomous power sources (voltage inverters), characterized in that the solution is achieved by a resistor limit on the set time of the starting current amplitude of the load motor below the protection response value IN (UPS), but not lower than the value at which the engine can still start and spin up, and which can be used as a simple circuit solution. Use with voltage inverters and medium and high power uninterruptible power supplies.

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