JPS6310075B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in an excitation device that excites a field winding of a hoist using a DC motor.

In general, the field of a hoisting machine using a DC motor, that is, a hoisting machine of a DC elevator, is excited at the rated field current only when the elevator is in operation, and when the elevator is stopped, it is excited at several tens of the rated field current. % current is being applied. This is to eliminate the delay in elevator startup time due to the delay in the rise of the field current.

Figure 1 is a circuit diagram of a conventional exciter. The size is set to allow the rated current to flow through the wire 7. 3 is a full-wave rectifier that converts the AC output power of the single-phase transformer 2 into DC power, and 4 is an electromagnetic contactor (not shown) that is energized when the elevator is in operation, regardless of whether the elevator is running or stopped. 5 is a normally open DC contact of an electromagnetic contactor (not shown) that is energized when an operation command is issued to the elevator and continues to energize until the elevator stops; 6 is a normally open DC contact for current limiting. The resistor 7 is the field winding of the hoist.

In the conventional device shown in FIG. 1, when the elevator stops, only the DC contact 4 of the magnetic contactor closes, and the field current limited by the resistor 6 excites the field winding 7 for weak excitation. , when an operation command is issued to the elevator, the resistor 6 is short-circuited by closing the contact 5 of the electromagnetic contactor, and the rectifier 3 is connected to the field winding 7.
Apply all of the output voltages to quickly achieve rated excitation.

However, this conventional device has the following drawbacks.

(1) The current limiting resistor 6 has a large capacity and is expensive, and also generates a large amount of heat, making the exciting device large.

(2) When the elevator stops operating, power is wasted in the resistor 6.

(3) An expensive DC magnetic contactor that can directly turn on and off DC current is required.

For this reason, for example, a rectifier circuit as shown in FIG. 5 described in Japanese Patent Application Laid-Open No. 55-80658 concerning an excitation circuit for an electromagnetic brake is configured, and when the contact 20 is closed, the coil 21 is set to the rated voltage of full-wave rectification. On the other hand, when the contact 20 is open, a low half-wave rectified voltage is applied to the coil 21, and the current limiting resistor is omitted.
Since this switching contact 20 will definitely be inserted into the DC circuit, it is still necessary to use the contact of an expensive DC magnetic contactor, and in order to prevent current from flowing through the coil 21. However, there remains a drawback that a DC contact 22 with high contact reliability is also required separately.

The present invention has been made in view of the above points, and it not only eliminates wasteful power consumption, but also enables direct current to be turned on and off, such as an expensive DC electromagnetic contactor with special consideration for contact reliability. A highly reliable excitation device for a hoisting machine that does not require any equipment and can avoid the worst case scenario in which the field winding is no longer energized and the driving force is lost even if a contact failure occurs at one of the contacts. The purpose is to provide

FIG. 2 is a circuit diagram of an excitation device showing an embodiment of the present invention, in which the same reference numerals as in FIG. 1 indicate the same components. 8 is a single-phase transformer having a low voltage tap a for weak excitation and a high voltage tap b for rated excitation as a secondary voltage output with respect to the reference potential terminal C;
9 is a normally open AC contact of an electromagnetic contactor (not shown) which is energized when the elevator is in operation, regardless of whether the elevator is running or stopped, similar to the contact 4 of the conventional device; 10 is a contact of the conventional device 5, a normally open AC contact 11A, 11 of an electromagnetic contactor (not shown) is energized when an operation command is issued to the elevator and continues to energize until the elevator stops.
B, 11C are three arms of a rectifier in which at least two rectifiers are connected in series, and these three arms 11A, 11B, 11C and the field winding 7 are respectively connected in parallel, and arm 11A and arm 11C are connected in parallel. A single-phase full-wave rectifier for rated excitation is configured by these, and a single-phase full-wave rectifier for weak excitation is configured by arm 11B and arm 11C. That is, when the elevator is stopped, only the AC contact 9 of the electromagnetic contactor for weak excitation is closed, and the weak excitation low voltage of the transformer 8 rectified by the single-phase full-wave rectifier composed of arms 11B and 11C is closed. A voltage output is applied to the field winding 7 to perform weak excitation, while when the elevator is in operation, an operation command is issued to the elevator, and the AC contact 10 of the electromagnetic contactor for rated excitation is closed, and the arm 11A is ,11B,1
The high voltage output for rated excitation and the low voltage output for weak excitation of the transformer 8 are applied to 1C, respectively, but the two diodes D ₃ and D ₄ that make up the arm 11B are connected to the two diodes D that make up the arm 11A. ₁ ,
Since a reverse bias is always applied by the function of D ₂ , only the rated excitation high voltage output of the transformer 8 is rectified by the single-phase full-wave rectifier composed of arms 11A and 11C, and the field winding 7 The rated excitation applied to the

Therefore, each terminal a, b, c of such a tap transformer 8 and three arms 11A, 11B,
If the configuration is such that the series connection points of each rectifier of 11C are connected via contacts, the voltage applied to the field winding of the hoisting machine can be changed by opening and closing these contacts, just like switching the taps of a transformer. In addition to eliminating the current-limiting resistance in conventional devices, switching between weak field excitation and rated excitation can be done using an inexpensive AC magnetic contactor that does not place much stress on the contacts. can be made possible. Also, even if one of the AC contacts 9a, 9c, and 10 should have a contact failure while the elevator is running (the probability of two or all three contact failures being extremely low), the three arms 11A, In the worst case, the driving force disappears even though the field is lost and the armature current increases extremely because some voltage is applied to the field winding by either two arms of 11B and 11C. It is also possible to construct an extremely safe field circuit that can avoid such situations.

Next, FIG. 3 shows another embodiment of the present invention.
In the figure, 11A' indicates two thyristors SCR1 and SCR2.
12 is a current detector that detects the field current flowing through the field winding 7; 13 is a current detector for igniting the arm 11A' according to the deviation between the rated current command value 14a and the detected current value 12a; This is a current control device that outputs a pulse signal 13a, and the same reference numerals as in FIG. 2 indicate the same ones.

In this embodiment, when the elevator stops,
Similar to the embodiment shown in Fig. 2, the field winding 7 is weakly excited by the single-phase full-wave rectifier composed of arms 11B and 11C, but when the elevator is operating, the field current matches the rated current command value. As shown in FIG. 4, the thyristor of the arm 11A' is fired with an appropriate control delay angle by the firing pulse signal 13a of the current control device 13, and a voltage Vo is applied to the field winding 7. be done. That is, ignition pulse signal 1
In power section X where 3a is not input, single-phase transformer 8
Low voltage tap a output for weak excitation of arm 11
B, 11C and is applied to the field winding 7. On the other hand, in the power supply section Y after the ignition pulse signal 13a is input, the rated excitation high voltage tap B output of the single-phase transformer 8 is applied to the arm 11A. ', 11C and is applied to the field winding 7, and a constant and stable rated field current flows through the field winding 7, regardless of changes in resistance due to temperature rise of the winding.

With the configuration described above, not only can all the drawbacks of the conventional device be eliminated, but also the field magnetic flux of the hoist can be kept constant while the elevator is running.
Even if the resistance of the field winding 7 changes with temperature, it will not adversely affect elevator speed control. Furthermore, even if the current control device 13 or the thyristor of the arm 11A' should fail while the elevator is running, a weakening field current will flow through the field winding 7, just as in the case where only the contact 10 has a contact failure. ,
It is extremely safe as the field magnetic flux does not disappear.

As described above, according to the present invention, three arms in which at least two rectifiers are connected in series constitute a rectifier bridge in which at least two rectifiers are connected in parallel, and the series connection point of the rectifiers in these arms is connected to the tap. Connect each terminal of the transformer via contacts,
Since the voltage applied to the field winding of the hoist is changed by opening and closing this contact, it is possible to not only eliminate the current-limiting resistance that was previously necessary, but also to switch between weak field excitation and rated excitation. The circuit can be configured so that the AC contacts of the AC electromagnetic contactor can be used, which is inexpensive and does not place much burden on the user and is less likely to fail. Furthermore, even if one of the switching contacts should have a contact failure while the elevator is running, the field of the field winding will not be completely lost, thereby providing an extremely safe excitation device for the hoisting machine. You can also do it.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a conventional excitation device, FIG. 2 is a circuit diagram of an excitation device showing one embodiment of the present invention, and FIG. 3 is a circuit diagram of an excitation device showing another embodiment of the present invention. FIG. 4 is a voltage waveform diagram applied to the field winding during elevator operation in FIG. 3, and FIG. 5 is a diagram showing an example of a conventional electromagnetic brake circuit. 2, 8...Single phase transformer, 3...Full wave rectifier, 4,5
...DC contact of electromagnetic contactor, 6...Resistor, 7...Field winding, 9, 10...AC contact of electromagnetic contactor, 11
A, 11A', 11B, 11C...Arm, 12...
Current detector, 13... Current control device, a... Low voltage tap, b... High voltage tap, c... Reference potential terminal.

Claims (1)

[Claims] 1. A transformer that supplies power to a field winding of a hoisting machine of a DC elevator via a full-wave rectifier, wherein the secondary output of the transformer has a reference potential, Three terminals are provided, a low voltage tap and a high voltage tap, and the full wave rectifier is constructed by connecting three arms in parallel, each of which has at least two rectifiers connected in series, and is connected to the high voltage tap terminal of the transformer. The series connection point of the two rectifiers in the first arm of the three arms is connected via a first AC contact that is closed until the DC elevator is stopped when an operation command is issued to the DC elevator. At the same time, the series connection point between the two rectifiers in the second and third arms of the three arms, and the low voltage tap terminal and reference potential terminal of the transformer are connected to the operation and stop of the DC elevator. An excitation device for a hoisting machine, characterized in that the excitation device is connected via a second AC contact that closes when the DC elevator is in operation regardless of the state. 2. Claim 1, wherein the rectifier constituting the first arm is a thyristor.
Excitation device for the hoisting machine described in Section 1.