JPS596158B2 - Commutatorless motor failure detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a failure detection device for a commutatorless motor, particularly for quickly detecting a failure of a rotary rectifier that excites a field.

[Background of the invention]

Generally, in order to excite the field of a relatively large-capacity commutatorless motor, the secondary voltage of a rotating induction device such as an induction motor or a rotating transformer is rectified by a rotating rectifier.

FIG. 1 is a configuration diagram showing an example thereof.

In FIG. 1, 1 is an AC power source, 2 is a forward converter, 3 is a DC reactor, and 4 is an inverse converter, and these 2 to 4 constitute a frequency converter.

5 is a synchronous motor driven by a frequency converter.

The rotating shaft of the synchronous motor 5 is provided with an induction machine T and a rotary rectifier 8 for brushless excitation of the field. The induction machine 7 is normally excited in the opposite phase, and as the rotation speed increases, the secondary voltage also increases. 11 is a voltage control circuit connected to the primary side of the induction machine □, and a saturable reactor or thyristor circuit is used.

In the following explanation, a case will be explained in which a saturable reactor is used. The field current command signal from the field current setting device 11 is detected by the current detector 12 and matched with a feedback signal converted into a DC signal by the rectifier circuit 13, and the current deviation is amplified by the amplifier 14. . The current deviation signal is applied to an automatic pulse phase shifter 15. Automatic pulse phase shifter 15
controls the firing phase of the reactor control forward converter 16 in accordance with the current deviation signal. The output voltage of the saturable reactor 17 is determined by the output of the forward converter 16, that is, the induction motor □
control the primary voltage of the Controlling the primary voltage of the induction machine 7 means controlling its secondary voltage, and as a result, the field current flowing through the field winding 6 of the synchronous motor 5 can be adjusted. 10 is a field AC power source.

By controlling the primary voltage of the induction machine to excite the synchronous motor in this manner, the field current can be made constant regardless of the rotation speed, but the following problems exist.

When the rectifier of the rotary rectifier 8 breaks down during operation of the commutatorless motor, the field current decreases.

The back electromotive force of the synchronous motor 5 decreases as the field current decreases. Due to the decrease in the back electromotive force of the synchronous motor 5, the thyristor of the frequency converter (inverse converter 4) fails to commutate. If the frequency converter fails in commutation, the commutatorless motor will naturally stop operating. Then, the broken down rectifier needs to be replaced. It is conceivable that the breakdown of the rectifier constituting the rotary rectifier 8 is detected when the frequency converter fails in commutation.

However, commutation failure in frequency converters can also occur due to other causes such as insufficient commutation margin angle or overcurrent.

Therefore, it is difficult to quickly detect breakdown of the rotary rectifier simply due to commutation failure of the frequency converter. Furthermore, in order to quickly detect breakdown of the rotary rectifier, it is conceivable to directly detect the field current of the commutatorless motor via a slip ring.

However, this goes against the trend of brushless technology. [Object of the Invention] The present invention has been made in view of the above-mentioned problems, and its object is to provide a failure detection device for a commutatorless motor that can promptly detect breakdown of a rectifier constituting a rotary rectifier. It is about providing.

[Summary of the Invention] The present invention is characterized by detecting the primary voltage of a rotating induction device that is controlled so that the field current of a synchronous motor becomes a command value, and detecting the primary voltage of a rotating induction device that is controlled so that the field current of a synchronous motor becomes a command value, and detecting the primary voltage when this primary voltage becomes less than the set value. Accordingly, breakdown of the rectifier constituting the rotary rectifier is detected.

[Embodiments of the invention]

FIG. 2 shows an embodiment of the present invention.

In Figure 2, the same symbols as in Figure 1 indicate equivalents, 20 is an isolation transformer that insulates and detects the primary voltage of the induction machine 7, 21 is a rectifier circuit, 22 is a filter, and 23 is an induction circuit. 24 is a comparison circuit 23 which generates an output (failure detection signal) when the primary voltage E1 of the machine 7 becomes lower than the set value E3.
This is a storage circuit that stores and displays the failure detection signal of , and provides it to the gate circuit 25 at the same time.

When the gate circuit 25 receives the failure detection signal stored in the memory circuit 24, it blocks the gate signal applied to the forward converter 2. In this configuration, when the rectifier of the rotary rectifier 8 breaks down while the synchronous motor 5 is operating, the primary current of the induction machine 7 increases. When the rectifier of one arm of the rotary rectifier 8 breaks down, the secondary side of the induction machine 7 becomes short-circuited between phases. The primary current of induction machine 7 is 2
It tends to increase due to a short circuit between phases on the next side. However, the voltage control circuit 17 lowers the primary voltage of the induction machine 7 and controls the primary current to a field current command signal (constant value). In this way, the primary voltage of the induction machine 7 is changed to the rotary rectifier 8.
due to rectifier breakdown. The inventors used a saturable reactor as the voltage control circuit 17,
According to actual measurements in the case where the rotary rectifier 8 has three phases, when the rectifier of one arm breaks down, the primary voltage of the induction machine drops to less than half of the normal voltage. induction machine 7
The primary voltage E1 of is detected by the isolation transformer 20, and the rectifier circuit 2
1 and then smoothed by a filter 22.

A comparison circuit 23 compares this primary voltage E1 with a set value Es. When Es>E1, the comparison circuit 23 outputs a failure detection signal, which is stored in the storage circuit 24 and displayed. Further, the gate circuit 25 shifts the gate signal of the forward converter 2 according to the failure detection signal stored in the memory circuit 24. to do). Thereby, commutation failure of the inverter 4 due to insufficient field current can be prevented. In this way, the breakdown of the rectifier constituting the rotary rectifier 8 is detected based on the magnitude of the primary voltage E1 of the induction machine 7, and the set value Es given to the comparator circuit 23 will be explained.

A simplified equivalent circuit of the induction machine 7 including the field winding 6 is shown in FIG.

If the primary leakage impedance X1 and the secondary leakage reactance X2' are ignored because they are small, the primary input impedance Z, which is the ratio between the primary voltage E1 and the primary current 11 of the induction machine 7, can be expressed by the following equation.

Here, Xnl is the excitation reactance, j is the imaginary unit, and R
2' is the primary conversion value of the secondary resistance, RI is the primary conversion value of the value obtained by converting the resistance of the field winding 6 to the secondary resistance of the induction machine 7, and S is the slip of the induction machine 7.

The generally used induction machine 7 is Xm〉Shirochimi, and if the excitation reactance Xrn is ignored, equation (1) can be expressed as follows.

In equation (2), secondary resistance R2' and field winding resistance Rf'
Ignoring changes due to temperature, the input impedance Z
is inversely proportional to the slip S.

The primary voltage E1 is the product of the primary current 1 and the impedance Z, as shown in equation (1).

Therefore, the primary voltage E1 is inversely proportional to the slip S. The induction machine 7 is excited in reverse phase so that the secondary voltage increases in proportion to the rotation speed.

The speed control range of the synchronous motor 5 is normally in the range of 1 to 1.5 when converted to the suberi S of the induction machine 7. Rotating rectifier 8
When in good condition, the primary voltage E1 is 67%p-100%
Varies between. On the other hand, in the case where the rotary rectifier 8 has three phases, the primary voltage E1 when the one-arm rectifier breaks down was actually measured and found to have decreased to 50% or less.

Therefore, by setting the set value Es given to the comparison circuit 23 to a value of 50% of the primary voltage when the slip S is 1, breakdown of the rectifier constituting the rotary rectifier 8 can be detected. In this way, breakdown of the rectifier of the rotary rectifier is detected when the primary voltage of the induction machine drops below the set value, so it can be detected quickly.

Next, FIG. 3 is a block diagram showing another embodiment of the present invention.

Differences in Figure 3 from Figure 2 - Senkeh^^/T
Smu 1 Δre 1 no 1 h ^ ri Kosen Sarayama no force (primary voltage E,)
A divider 26 that divides the output signal (primary current 11) of the rectifier circuit 13, and a comparison circuit 27 that generates an output when the input signal falls outside a predetermined range are provided.

In equation (2), usually Rf>R2', and the secondary resistance r
! Ignoring , the primary input impedance Z can be expressed by the following equation.

The speed control range of the synchronous motor 5 is a predetermined range, and the range of change in impedance Z is also within a predetermined range.

However, when the rectifier of the rotary rectifier device 8 breaks down, the secondary side of the induction machine 7 becomes short-circuited by the broken down rectifier, and the impedance Z becomes small. Therefore, a breakdown can be detected by determining that this change is outside a predetermined range.

The divider 26 is for detecting that the values of the primary voltage E1 and the primary current 11 are outside the normal variation range of the rotary rectifier 8. In this embodiment as well, since the primary current 1 is controlled to be constant, it goes without saying that a decrease in the primary voltage E1 of the induction machine 7 is detected. FIG. 4 shows yet another embodiment of the invention, in which a rotary transformer 30 is used in place of the induction motor 7, and its operation is similar to that of FIG. [Effects of the Invention] As described above, according to the present invention, breakdown of the rectifier in the rotary rectifier can be promptly detected by detecting that the primary voltage of the rotary induction device has fallen below the set value. .

In the above embodiments, the frequency converter is constructed by combining a forward converter and an inverse converter, but it goes without saying that the present invention can also be applied to a cycloconverter.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a conventional device, FIG. 2 is a block diagram showing one embodiment of the present invention, FIGS. 3 and 4 are block diagrams showing other embodiments of the present invention, and FIG. It is a simple equivalent circuit diagram. 2... Forward converter, 3... DC reactor, 4... Inverse converter, 5... Synchronous motor, 6... Field Magnetic winding, 7... Induction motor, 17... Voltage control circuit, 23...
Comparison circuit, 24... Memory circuit.

Claims (1)

[Claims] 1 A frequency converter composed of multiple thyristors,
A synchronous motor driven by the frequency converter; a rotary induction device having a primary winding and a secondary winding mechanically connected to the synchronous motor and magnetically coupled; A non-rectifying device comprising a rotary rectifier that rectifies a secondary voltage and excites the field of the synchronous motor, and a voltage control circuit that controls the primary voltage of the rotary induction device and sets the field current to a command value. In the sub motor, a voltage detection means for detecting the primary voltage of the rotary induction device controlled by the voltage control circuit compares the primary voltage detected by the voltage detection means with a set value, and determines whether the primary voltage is the set value. 1. A failure detection device for a commutatorless motor, comprising: comparison means that produces an output when the value falls below a value, and detects a failure of the rotary rectifier based on the output of the comparison means.