JPS59149789A - Scherbius device - Google Patents

Abstract

PURPOSE:To reduce the loss and to reduce the rated current value of a DC reactor by removing a DC reactor from a circuit in a range for stably operating in Scherbius action even if no DC reactor is presented. CONSTITUTION:In a device having a rectifier 2 for converting an AC voltage induced in the secondary winding of an induction motor into a DC voltage, a DC reactor 3 for reducing the pulsating current, and an inverter 4 for inverting the output DC voltage into an AC voltage to return power to an AC power source, a stationary Scherbius device having a current detector 7 for measuring a current provided in the output AC circuit of the input DC circuit of the inverter 4, and a switch 6 for shortcircuiting the reactor 3 when the detector 7 detects the current value equal to or higher than the preset current value can be obtained.

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to reducing energy losses in stationary Servius devices.

[Technical background of the invention and its problems] Conventional stationary Servius devices have always incorporated a DC reactor 3 into the circuit, as shown in FIG.

This DC reactor 3 is used in order to reduce the ripple current caused by the inverter 4c of the DC current flowing between the rectifier 2 and the inverter 4.

Reduce this pulsating flow, confidence 1! This is necessary to prevent the current from becoming zero depending on the magnitude of the pulsating current and the magnitude of the DC average current.

If this pulsating current is not reduced and the DC current periodically becomes zero (f2), that is, the DC current flows intermittently, the current control by the inverter 4 becomes impossible, resulting in a speed C2. It's too bad that it's out of control.

However, for most of the loads to which a stationary Servius device is applied, the load reaction torque τ increases as well as the speed increases.For example, pumps, blowers, etc. increases.

Also, the torque τ of the wound induction motor 1 and the secondary current ■2
The following relationship holds true between .

τα Engineering 2 −−−−−−−−−−−−−− (
1) Therefore, if the DC current is made more o, then T(is made more C)--------(2) also holds true.

That is, it can be said that O from the direct current of a stationary Servius device increases as the speed increases.

From the average value of this pulsating DC current, O and 50 of the pulsating current.
As shown in FIG. 3, when the inverter 4 controls the DC voltage to zero, α becomes the maximum value C;

Here, 1... Direct current (instantaneous value) L... Circuit transfer actance when looking at the motor from the inverter side ET... Inverter side voltage effective value θ of the inverter transformer... When the inverter side voltage of the inverter transformer f...Power supply frequency t...Time (seconds), the following relational expression holds true.

e = J2 Ets stone (2πft)
−−−1−−(Alalso +3” L tan at −−−−−−−−−(41 Therefore, JT Eis+n(2πft) = L tan−−−
−+51t Integrating both sides of the above equation, we get −−−−−−−−−−−<1) Since the ratio of the pulsating current work Inc to one pair is α (0 to peak value), the work work − work = Since o X 2α ------- (8), since the DC current is not intermittent, it is necessary that 1''-by α<1, so the following inequality holds true.

The reactance defined by the right-hand side of this inequality usually has a value smaller than the actance of the motor when viewed from its secondary terminal.

This fact indicates that the DC current will not be intermittent even if the DC reactor 3 is not applied when the Cervius device is operated at near the maximum speed.

However, in the past, a DC reactor 3 whose ni reactance was determined was always used so that the DC current would not be interrupted over the entire speed control range.

In this case, since current flows through the DC reactor 3I even in an operating range where the DC reactor 3 is not required, the loss due to the DC reactor 3 always becomes part of the loss of the device.

In addition, since the maximum DC current is taken into consideration in the design of the DC reactor 3, the iron core and conductor must be made larger, resulting in no need for equipment; expensive and reduces loss during operation. I was making it big.

[Objective of the Invention] In light of the above, the object of the present invention is to eliminate loss due to the DC reactor by not passing current through the DC reactor in speed region 1-, where stable speed control can be performed without using a DC reactor. And C2, it is an object of the present invention to provide a stationary Servius device in which the maximum value of DC reactor acoustic current is reduced and the DC reactor is designed to have a smaller iron core size and conductor size.

[Summary of the Invention] The present invention provides an induction motor having a secondary winding with a cotrochanter, a rectifier that replaces an AC voltage induced in the secondary winding C2 of the induction motor with a DC voltage C2, and In the Serbius device, which consists of a DC reactor that reduces ripples in the output DC current of the rectifier, and an inverter unit that converts the output DC voltage of the rectifier back into AC voltage and returns the AC power C, the inverter A current detection device that is installed in the output AC circuit or input DC circuit of the device and measures the current, and a switching device that activates a CTti flow reactor when this current detection device detects a current value that is equal to or higher than a preset current value. This is a Servius device equipped with.

That is, the present invention uses a Servian device C2, which is composed of a wound induction motor, a rectifier that converts its secondary output into a clear current 1''', a DC reactor, a thyristor inverter, and an inverter transformer, to convert the DC Servius is characterized in that a switch is connected in parallel with the reactor, and the switch is operated by a signal from a device that detects that the current value on the secondary side of the wound induction motor exceeds a certain current value. It is a device.

[Embodiments of the invention] Next, Example 1m of the present invention will be explained.

Figure 2 shows an induction motor 1 having a secondary winding in its rotor, a rectifier 2 that converts the AC voltage induced in the secondary winding of the induction motor 1 into a DC voltage, and the output DC current of the rectifier 2. Stationary Servius device C consisting of a DC reactor 3 that reduces pulsation and an inverter 4 that converts the output DC voltage of the rectifier 2 into an AC voltage c and returns the power to the AC power source. A current detection device 7 that is installed in the circuit or input DC circuit and measures the current, and an opening/closing device that short-circuits the C2 DC reactor 3 when the current detection device #7 detects and outputs a current value greater than a preset current value. 6 shows a stationary Servius device comprising a container 6.

That is, in the present invention, as shown in FIG. 2, a switch 6 is connected to the DC reactor 3 in parallel 111''', and a current detection device 7 is provided.

When operating in the speed control region C where the direct current flowing in proportion to the torque of the rectangular cylinder and the actance seen from the secondary terminal of the induction motor have the relationship expressed by equation (1o), the switch 6 is closed and the direct current is When the DC current does not flow through the reactor 3, the switch 6 is opened during operation in other areas, and DC current flows through the DC reactor 3.

[Effects of the invention] The present invention allows a stable Cerbius device even without a DC reactor. This has the effect of lowering the cost of the device.

In addition, in order to control the opening and closing of this switch, C2 is calculated by comparing the actual flowing value of O and the calculated value according to formula (10) from the average value of the DC current. For cases where the relationship between speed and torque is constant, there is a method of increasing or decreasing a specific speed and the actual speed.

[Brief explanation of the drawing]

FIG. 1 is a circuit configuration diagram of a conventional Servius device, and FIG. 2 is a circuit configuration diagram of a Servius device showing an embodiment of the present invention.
FIG. 3 is an explanatory diagram of pulsating DC current. 1... Induction motor 2... Rectifier 3... DC reactor 4... Inverter 6... Switch
7...Current detection device representative Patent attorney Kensuke Chika (and 1 other person) Figure 1

Claims (1)

[Claims] An induction motor having a secondary winding in its rotor, a rectifier that converts an AC voltage induced in the secondary winding of the induction motor into a DC voltage, and a rectifier that reduces ripples in the output DC current of the rectifier. In the Serbius device IT2, which consists of a DC reactor and an inverter device that converts the output DC voltage of the rectifier into AC voltage and returns the AC power,
Output AC circuit or input DC circuit of the inverter device≦
A Servius device comprising: a current detection device that is split into two to measure electrophoresis; and a switching device that short-circuits the DC reactor when the current detection device detects a current value greater than a preset current value.