JPS5947993A - Control circuit for centrifugal machine - Google Patents

Abstract

PURPOSE:To effectively accelerate slowly a centrifuge by providing a mixed bridge which has a phase controller, a rectifier of two thyristors and two diodes and switching between half-wave phase control and half-wave rectification at the slow accelerating time of a motor. CONSTITUTION:A mixed bridge circuit is composed of two thyristors and two diodes 7, thereby controlling the DC motor 3 of a centrifugal machine. A rotating speed detector 4 detects the rotating speed of the motor 3, applies it to a gate controller 8, which outputs a gate signal to a thyristor 6. When the motor 3 is slowly accelerated, one of two thyristors 6 is idled, the mixed bridge circuit is controlled in half-wave phase and operated in half-wave rectification. After the motor 3 reaches the prescribed speed, it is controlled in full-wave phase and operated in full-wave rectification. In this manner, even if the waveform of the power source is deformed, the motor can be effectively slowly accelerated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control circuit for a centrifuge, and particularly to a control circuit suitable for reliably achieving slow acceleration even when the waveform of a power supply is distorted.

In recent centrifugation methods, particle rotors are used to shorten centrifugation time. but,
When using this rotor, accelerate the rotor very slowly (experimentally about 3 minutes) to about 1100 llrp (llrp: about 3 minutes) in order not to disturb the density gradient liquid in the tube.
It is necessary to do so.

By the way, the drive control circuit for the electric motor of the conventional centrifuge is
The circuit configuration was as shown in the figure. In Figure 1, 1 is a phase control element (such as FLS (bidirectional control rectifier)).
A voltage regulator may also be used. ), 2 is a full-wave rectifier, 6 is a DC motor, 4 is a rotation speed detector that detects the rotation speed of the motor 6,
5 is a gate control circuit that outputs gate signals of FI and S i.

In other words, in order to achieve high speed and high output, the DC motor 6
After performing phase control with FLS1, full-wave rectification was performed with rectifier 62, and the DC voltage supplied to @current motor 3 was gradually increased.

Figure 2 shows the voltage waveform during phase control in the case of Figure 1, D″L
This is a diagram showing the firing angle and motor current waveform of S, where (a) is the voltage waveform, (b) is the firing angle, and (C) is the current waveform.

By the way, as mentioned above, 11000 rpm over 6 minutes
In order to achieve slow acceleration up to the point where the firing angle β is as small as possible (close to the synchronization point), the acceleration current flowing through the DC motor 3 should be set at 1.5~2. Must be controlled to OA position. However, since the phase of the ignition pulse is extremely close to the synchronization point, if the synchronization point shifts due to distortion of the power supply voltage waveform, even if the ignition angle is controlled, the next half cycle of the power supply will be delayed. There are problems in that it is not easy to adjust the ignition angle, such as when the ignition start pulse is incorrectly ignited, causing an excessive acceleration current to flow.

The present invention has been made in view of the above, and its purpose is to provide a control circuit for a centrifuge that can achieve reliable (C slow acceleration) even if the waveform of the power supply is distorted.

A feature of the present invention is that a phase control circuit that controls the phase of alternating current and a rectifier that converts the phase-controlled alternating current into direct current and supplies it to the motor of the centrifuge are connected to two cyrisks and two rectifiers. a mixed bridge circuit consisting of a diode, and half-wave phase control with one of the two thyristors left idle during slow acceleration of the motor;
The present invention is characterized in that it is equipped with a switching means that performs half-wave rectification operation and, after the motor reaches a predetermined rotational speed, switches to full-wave phase control and full-wave rectification operation.

The present invention will be described in detail below with reference to the embodiment shown in FIG. 3 and FIG. 4.

FIG. 3 is a block diagram showing an embodiment of a control circuit for a centrifuge according to the present invention. The same parts as in FIG. In FIG. 3, a gate control circuit 8 that configures a mixed bridge circuit with two thyristors 6 and two diodes 7 and outputs a gate signal to thyristor B is not shown. When slowly accelerating the DC motor 6 of the centrifuge to 11,000 rpm in about 3 minutes, for example, one of the two cyrisks is used as a play, and the mixed Pritsuno circuit is operated with half-wave phase control and half-wave rectification. For example, the electric motor 6 has a speed of 11000 rpm.
After reaching a predetermined rotational speed, the mixing bridge circuit is provided with a switching means for switching between full-wave phase control and full-wave rectification operation.

Figure 4 is a diagram showing half-wave phase control, voltage waveform during medium-wave rectification operation, firing angle of Cyrisk 6, and motor current waveform in the case of Figure 3, where (a) is the voltage waveform, (b) is the firing angle, (C
) is the current waveform. Since it is a half-wave power supply, in order to flow the same accelerating current as in the case of Figure 1, it is necessary to open the firing angle of thyristor 6 to the limit), which means that the firing angle control is extremely difficult. This shows that it can be easily achieved, and since there is no next half cycle, there is no need to worry about firing errors as explained using FIG.

It goes without saying that in order to make one thyristor of the two thyristors idle, the circuit of that thyristor may be cut off in addition to stopping the supply of the gate signal.

As explained above, according to the present invention, there is an effect that slow acceleration can be reliably realized even if the waveform of the power supply is distorted.

[Brief explanation of drawings]

Figure 1 is a drive control circuit diagram of a conventional centrifuge motor;
The figure shows the voltage waveform, firing angle, and motor current waveform in the case of Fig. 1. Fig. 6 is a block diagram showing one embodiment of the control circuit of the centrifuge of the present invention. 2 is a diagram corresponding to FIG. 2 in the case of FIG. 3--DC motor, 4--Rotation speed detector, 6--Thyristor, 7-Diode, 8--Gate control circuit. Name of patent applicant Hitachi Koki Co., Ltd. 1st leap! ZffjfJ = (C) 37th 4th leap (C) 1 “

Claims (1)

[Claims] 1. A phase control circuit that controls the phase of alternating current, a gate control circuit that outputs gate signals for the constituent elements of the phase control circuit, and a gate control circuit that converts the phase of the alternating current controlled by the phase control circuit into direct current to operate the centrifuge. A control circuit for a centrifuge comprising a rectifier that supplies an electric motor, and a rotation speed detector that detects the rotation speed of the electric motor and provides an output signal to the gate control circuit, wherein the phase control circuit and the rectifier are provided in two pieces. A mixed bridge circuit consisting of a thyristor and two diodes is used, and when the motor is slowly accelerated, one of the two thyristors is used as a play, and half-wave phase control and hand rectification are performed, so that the motor is in a predetermined state. A control circuit for a centrifuge, characterized in that it is equipped with switching means for switching between full-wave phase control and full-wave rectification operation after reaching the rotational speed.