JPH0678592A - Protective circuit of motor - Google Patents

Abstract

PURPOSE:To compensate a decrease in a torque, to perform sufficient kneading and to prevent burning of a motor by detecting a motor current and applying a phase advancing capacitor in parallel with a capacitor of an auxiliary winding of the motor when an overload state is detected in a kneading capacitor for bread making material, etc. CONSTITUTION:When a material viscosity is raised during kneading of a bread material, a speed of a motor 11 is reduced, a motor current is increased to become an overload state. This motor current is detected by a CT 3, converted to a DC voltage by a diode 4 and a smoothing capacitor 5, compared with a reference voltage by a comparator 6, and an overload detection signal is received by a controller 8 to judge a load state of the motor 11 and kneading time of the material, a signal is sent to a relay switch 2, a phase advancing capacitor C1 is connected in parallel with the capacitor C of an auxiliary winding 9 to increase an output torque of the motor 1, thereby continuing the kneading.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a protection circuit for a motor of a kneading device for kneading bread dough or the like, and more particularly to a protection circuit for protecting the motor when the motor for kneading is overloaded.

[0002]

2. Description of the Related Art FIG. 3 shows a kneading motor circuit of a conventional bread maker. When the bread-making material is put into the baking case (not shown) of the bread-making device and the kneading operation of the material is started, the control unit 100 turns on the normally-open relay 101 and the kneading motor 1
A power source is applied to 02 to start the kneading of bread ingredients.

As the bread material is kneaded to increase its viscosity and hardness, the kneading motor 102 gradually becomes overloaded, its speed decreases and its torque decreases, and finally an excessive current flows. The winding temperature of the kneading motor 102 rises,
The temperature fuse (or thermal relay) 103 of the kneading motor 102 is cut off to cut off the power supply to stop the kneading motor 102 for protection.

[0004]

However, in the prior art shown in FIG. 3, the kneading of the bread material of the bread maker is an important step in the initial stage, and the viscosity of the bread material varies and the viscous hardness varies. If it is too high, if the kneading motor stops the kneading operation before it is sufficiently kneaded, it may hinder the baking of the bread, and the motor winding may be burned before it stops. there were.

The present invention has been made in view of the above problems, and a motor that automatically compensates for a decrease in torque of a kneading motor to enable a sufficient kneading that is set and prevent burnout of the motor. The purpose is to provide a protection circuit.

[0006]

In order to achieve the above object, the present invention provides a motor protection circuit of a kneading device for charging materials and kneading, and a motor for kneading,
Turning on / off the phase advancing capacitor connected in parallel with the capacitor of the auxiliary winding of the motor and the connection of the phase advancing capacitor.
F switch, current detection means for detecting the motor current of the motor, and the current value detected by the current detection means to determine the load state of the motor, and if the load state is over, turn on the switch. Is provided with a control unit for increasing the motor torque.

[0007]

With the above structure, the control section can always monitor the motor current by means of the current detection means, and when the control section judges that the motor is overloaded, the control section is provided in parallel with the auxiliary winding capacitor of the motor. The phase-advancing capacitor is connected to increase the torque due to the current phase difference generated between the main winding and the auxiliary winding of the motor and prevent the motor from burning due to the increased current during overload.

[0008]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of a motor protection circuit at the time of overload according to an embodiment of the present invention. In FIG. 1, C1 is a phase advancing capacitor connected in parallel to the capacitor C of the capacitor induction motor 11, and 2 is an ON / O switch for the phase advancing capacitor C1.
It is a relay switch for FF.

3 is a CT (current transformer) for detecting the motor current on the side of the main winding 10 of the motor 11, 4 is a rectifying diode, 5 is a smoothing capacitor, and 4 and 5 are DC.
A voltage conversion circuit, 6 is the output voltage of the DC voltage conversion circuit is Vc
c is a comparator that divides c into R1 and R2 and compares the reference voltage, and 7 is an amplifier that amplifies the detection voltage of the comparator 6. A current detection circuit is configured. Reference numeral 8 is a control circuit for judging the output signal of the amplifier 7 to turn ON / OFF the relay switch 2, 9 is an auxiliary winding of the equivalently shown capacitor induction motor 11, and 10 is a main winding for operation. . FIG. 2 is a speed characteristic curve of the motor shown in FIG.
The torque in the case only and the torque in the case where the phase advancing capacitor C1 is connected are shown in comparison. C is about 10-20μ
Since it is F, the value of compensation C1 is also determined according to the value of C.

Next, the operation will be described. When the viscosity of the material increases and the speed of the motor 11 decreases during kneading the bread material, and the torque decreases, the slip S approaches S = 1 as shown in the characteristic curve of FIG. The operating state moves to the left, and the motor current I (chain line display)
Is increased and becomes overloaded.

The increasing motor current I is detected by CT3, converted into DC voltage by the DC voltage conversion circuits 4 and 5, and compared with the reference voltage of the comparator 6. When the input voltage value exceeds the reference voltage value, the overload state occurs, so the comparator 6 outputs the overload detection signal, the detection signal is amplified by the amplifier 7, and is input to the control unit 8.

The control unit 8 controls the motor 11 based on the overload detection signal.
State and the kneading time of the bread material, a signal is sent to the relay switch 2 to connect the phase advancing capacitor C1 to C to increase the capacitance value, which is generated between the main winding 10 and the auxiliary winding 9. The torque is increased by the current phase difference as shown by the curve C + C1 in FIG. 2 to continue the kneading.

In this case, in the state of the motor 11, the torque approaches the steady operation region on the right side of the maximum torque point To shown in FIG. Therefore, the torque decreases until the motor 11 is in the stopped state such as S = 1 point in the overload maximum current state, and the operating point is away from the position where the maximum current value is reached, and the winding temperature rises due to the overcurrent. Then, the control unit 8 automatically adjusts the temperature fuse so that it operates in a state where there is no fear of disconnection. When the current value returns to normal, the phase advancing capacitor C1 is turned off again, and the normal operation is started.

In this embodiment, the detection circuit detects that the motor 11 is overloaded and the current increases, and the control unit 8 increases the series capacitance of the auxiliary winding 9, The load current of the motor 11 is automatically adjusted so that the rotating magnetic field is strengthened and the torque is increased by the current phase difference generated between the winding 10 and the auxiliary winding 9, so that the kneading process of the bread maker is sufficiently compensated. However, the motor 11 can be protected from an excessive current when overloaded.

[0015]

As described above, according to the present invention,
A phase advancing capacitor that is connected in parallel with a capacitor that is connected in series to the auxiliary winding of the motor, a relay switch that turns ON / OFF the connection of the phase advancing capacitor, and a CT that detects the motor current from the main winding side of the motor. , A voltage conversion circuit that rectifies the detected current and converts it into a voltage, a comparator that compares the converted DC voltage with a reference voltage, and amplifies and outputs the output of the comparator to determine the overload condition of the motor and turn on the relay switch. Since the controller for increasing the torque by connecting the phase-advancing capacitor is provided, it is possible to prevent the motor from being damaged at the time of overload and to sufficiently compensate the kneading operation.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a motor protection circuit at the time of overload according to an embodiment of the present invention.

FIG. 2 is a speed characteristic curve diagram of the motor shown in FIG.

FIG. 3 is a configuration diagram of a kneading motor circuit of a conventional bread maker.

[Explanation of symbols]

 C1 Phase advance capacitor 2 Relay switch 3 CT 4 Diode 5 Smoothing capacitor 6 Comparator 7 Amplifier 8 Controller 9 Auxiliary winding 10 Main winding 11 Motor

Claims (1)

[Claims] 1. A motor protection circuit of a kneading device for charging materials and kneading, comprising: a motor for kneading; a phase advancing capacitor connected in parallel with a capacitor of an auxiliary winding of the motor; A switch for turning on / off the connection of the phase advancing capacitor, and a current detecting means for detecting a motor current of the motor,
A motor is provided with a control unit that determines the load state of the motor from the current value detected by the current detection means and turns on the switch in the overload state to increase the motor torque. Protection circuit.