JPS5837773B2 - hysteresis motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hysteresis smoke protection device that monitors the peak value of an active current to grasp the load condition of a motor and protect the motor.

Hysteresis smokes are used as small synchronous machines, but their electrical characteristics are significantly different from other electric motors.

Figure 1 shows the typical slip S versus torque T and current ■ characteristics of this hysteresis smoke.As can be seen from the figure, even if the slip S changes, the current I and torque T hardly change. .

This is because the power factor of hysterin smoke is extremely low at around 0.2, so even if the effective current increases a little []L, the current value itself hardly changes. /z It's because it's ugly.

This is a very advantageous characteristic, but on the other hand it is inconvenient in terms of protecting the hysteresis motor itself.

A hysteresis-rotor has only a small amount of hysteresis loss when the rotor is turned to synchronous speed, but overcurrent loss also occurs at speeds other than synchronous speed.

In the case of a structure in which it is difficult to sufficiently dissipate heat from the rotor, the temperature of the rotor increases significantly due to increased loss.
High temperatures of C or higher may be reached.

If the temperature becomes higher than this, the material of the rotor may deteriorate.
This will completely interfere with the operation of the machine.

Therefore, it is necessary to detect slippage and protect it from operating at speeds other than synchronous speed for long periods of time, and even at synchronous speed, it is necessary to detect the amount of load being applied and to protect it from operating under heavy loads. It is necessary to take all possible measures to prevent this from happening.

From L or Le, in a device that uses a large number of hysteresis smokes, it is economically disadvantageous to detect the speed of the motor one by one using, for example, a speed generator, and it may not be possible to measure it easily. .

On the other hand, with other types of motors, the magnitude of the current changes depending on the size of the load, so overloads can be easily detected using thermal relays, etc. As shown in Figure 1, in hysterin smoke, the current hardly changes depending on the load, which precludes the use of thermal relays, and for this reason there was no suitable protection device in the past.

by the way. It is known that in hysteresis smoke, the effective current is the smallest at synchronous speed, and increases when the synchronous speed is lost due to overload, etc.

Therefore, the load status can be grasped by monitoring the peak value of the effective current.

The present invention focuses on this point. The KL hysteria system samples and holds the magnitude of the current in the same phase at the time when it reaches the peak value of any fundamental wave phase voltage, and determines whether the motor is overloaded based on the magnitude of that value and performs protection. The purpose is to provide a smoke protection device.

An embodiment of the present invention will be described below with reference to FIG. 2 in the case where the R phase is used as the detection phase.

In the figure, HM is a hysteresis smoke powered by three-phase power supplies R, S, and T, 1 is a current transformer that detects the R-phase current, and 2 is a converter 1 that converts the output of this current transformer 1 into a voltage value. ta3iiS,
A voltage converter 4 detects the T-phase voltage, L*S is passed through a filter 5, and a zero point detector 6 detects the zero point of the T-phase voltage.
is a sample and hold circuit.

Next, to explain the operation, the electric voltage of the line ST is shifted by 90'Q phase with respect to the R phase, so the fundamental wave voltage of the line ST reaches the zero point at the time when the peak value of the R phase tonnage pressure is reached. pass.

The zero point is detected by a zero point detector 4.

The zero point detector 4 produces a pulse of a certain width as an output the moment its input becomes zero.

As is generally well known, the sample hold circuit 6 is a circuit that stores the input amount at the moment a pulse is applied to the gate.

Therefore, every time a pulse from the zero point detection circuit 4 enters, the converter 2
The amount of current converted to voltage is stored, and this value is updated every cycle.

In this way, at the time when the peak value of the phase voltage is maximum, the reactive current is zero and the active current shows the peak value, so the amount stored in the sample-and-hold circuit 6 is equal to the active current of each cycle. Being there is K.

Therefore, this value is compared with a set value that indicates an overload value, and if it exceeds this set value, it can be determined that an overload has occurred. It is possible to protect the area by removing it.

This method has the advantage that even if the current contains harmonics, since most of the harmonic currents are reactive currents, they do not interfere with detection.

As described above, according to the present invention, it is possible to accurately perform hysteresis smoke overload protection with a relatively simple structure and therefore economically.

Section E: In carrying out the present invention. If the number of hysteresis smokes is very large and providing a detection device like the one shown in Figure 2 for each motor would put pressure on economic efficiency,
A part or all of the converter 2, zero point detector 4, filter 5, and sample hold circuit 6 shown in the figure may be provided for each motor group, and switched in order according to a command from a computer.

In this case, the hysteresis smoke loses synchronization and generates heat.
The number of daloubs can be selected appropriately depending on the time required for separation for protection.

The method of sending a sample command to the sample hold circuit 6 is not only by detecting the voltage zero point between Vc8 and T as shown in Fig. A similar operation is possible by extracting and using the corresponding signal b from a part of the circuit.

In addition, various modifications can be made within the scope of changing the gist.

[Brief explanation of the drawing]

Figure 1 shows the slip vs. torque and current characteristic curves of the hysteresis smoke. FIG. 2 is a circuit diagram of an embodiment of the present invention. 1...Current transformer, 2...Current-to-voltage converter, 3...Voltage transformer, 4...Zero point detector, 5... ...Filter, 6...Sample and hold circuit.

Claims (1)

[Claims] 1 A circuit that sends a sampling command near 11 when the peak value of the voltage of at least one arbitrary phase of the human power source is reached, and a circuit that samples and stores the current value of the same phase from the sampling finger 4>2 from this circuit. A hysteresis smoke protection device is fully equipped with KL to take protective measures when the stored value of this circuit exceeds a certain level.