JPS61210896A - Scherbius speed controller - Google Patents

Abstract

PURPOSE:To enable a speed control without necessary of a tachometer generator mounted on a motor shaft as heretofore by electrically detecting a speed feedback signal. CONSTITUTION:A Scherbius speed controller has an instrument transformer 14 at the input side of a converter 3, and an instrument transformer 15 and a voltage detector 17 at the output sides of a voltage detector 15 and an inverter 4. A multiplier 18 multiplies the output of the detector 17 by the turn ratio of an inverter transformer 5 to obtain the primary side voltage of the transformer 5, i.e., a motor voltage. Then, a multiplier 20 multiplies the output of a multiplier 18 by the turn ratio of the motor 1 to obtain the secondary voltage when the motor stops. A divider 22 calculates 'a slip' of the motor from the outputs of the detector 15 and the multiplier 18, and a converter 23 converts the 'slip' calculated by the divider 22 into a signal capable of collating to a speed setter 8. Thus, an inverter 4 is controller.

Description

[Detailed description of the invention] [Technical field of invention] FIELD OF THE INVENTION The present invention relates to a Servius speed controller.

[Technical background of the invention and its problems]

FIG. 2 shows a conventional Servius speed control device.

A tachometer generator 7 is connected to the electric motor 1 via a coupling 6, and the speed command signal of the speed setting device 8 and the speed feedback signal from the tachometer generator 7 are matched, and the motor is controlled based on the deviation signal. 1 is speed controlled. The portion surrounded by a chain line in FIG. 2 is generally included in the Servius device board.

Servius devices have conventionally been widely applied to speed control of pumps, blowers, and the like. Speed control of pumps, blowers, etc. is ultimately fluid flow rate control, and there are few cases where precise speed control accuracy is required as in speed control of general processing machines.

Conventionally, in Serbius speed control devices, a tachometer generator is attached to the anti-load side shaft of a wound induction motor (hereinafter referred to as the motor) via a coupling as a speed detector.
This tachometer generator output is used as a speed feedback signal to perform speed control.

Therefore, external wiring work for control signals is required between the electric motor and the Serbius speed control device, which causes an increase in equipment costs. There is a disadvantage that control problems may occur due to breakage of the external wiring of the meter generator.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a Cerbius speed control device with improved reliability by improving the connection configuration between the electric motor and the Cerbius speed control device.

[Summary of the invention]

The present invention provides a converter connected to a secondary output side of an induction motor, and a secondary side of an inverter transformer connected in series to this converter and whose output side is connected to an input power source side of the induction motor. an inverter, a first voltage detector that detects the secondary voltage of the induction motor, a second voltage detector that detects the secondary voltage of the inverter transformer, and an output of the second voltage detector. is multiplied by the turns ratio of the inverter transformer and the turns ratio of the induction motor, and a calculation unit that calculates a secondary voltage when the induction motor is stopped; It is characterized in that a slip value is obtained by division, and this slip value is used as a speed feedback signal.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, an instrument transformer 14 and a voltage detector (VDI) for detecting the motor secondary voltage are connected to the input side of the converter 3.
15. An instrument transformer 16 and a voltage detector (V
H2) 17 is provided, and the output of the voltage detector (VH2) 17 is multiplied by the turns ratio of the inverter transformer 5 to obtain the number of primary windings of the inverter transformer 5, and a multiplier 18 for obtaining the motor terminal voltage. , a multiplier 20 for multiplying the output of the multiplier 18 by the winding ratio of the motor 1 to obtain the secondary voltage when the motor is stopped.
, a divider 22 for calculating the 1st value of the motor from the output of the voltage detector (VDI) 15 and the output of the multiplier 18;
1 slip ' calculated by the divider 22 is applied to the speed setter 8
A converter 23 is provided for converting the signal into a signal that can be matched. The constant setter 19 is used to set the winding ratio of the inverter transformer, and the constant setter 21 is used to set the winding ratio of the motor.

Now, if the terminal voltage of the motor 1 is El, the motor secondary voltage (when stopped) E2 is expressed by the following equation.

Here, NMl indicates the number of windings on the motor secondary side, and 8M2 indicates the number of windings on the secondary side of the motor.

Also, when the motor is rotating with slip % S t, the motor secondary voltage Es is Es=S-Es......-■ Therefore,
The motor secondary voltage changes in proportion to the slip ′″S′.

The present invention converts the secondary voltage Es of the electric motor 1 into the voltage transformer 14.
is detected by the voltage detector (VDI) 15. Furthermore, since the secondary voltage E2 when the motor is stopped varies depending on the terminal voltage actually applied to the motor 1, this terminal voltage E1 is applied to the secondary side of the inverter transformer 5. The voltage is obtained by converting the voltage obtained by the provided instrument transformer 16 and voltage detector (VH2) 17 to the primary side of the inverter transformer 5.

That is, if the output of the voltage detector (VH2) 17 is ET2, then E, = ET .
is the number of windings on the primary side of the inverter transformer 5, and NT2 is the number of windings on the secondary side.

Therefore, Ntz/Ntz are set in constant setters 19 and 21, respectively.
By setting pNM2/NMI and calculating with multipliers 18 and 20, E□ in formula (2) is obtained. Furthermore, divider 2
2, E3/Et is calculated, the slip ``s1'' is calculated, and 1 slip 1 of the electric motor 1 can be obtained. By converting this slip 18'' through the converter 23 into a signal level that can be compared with the speed setting device 8, and using this signal as a speed feedback signal, the tachometer generator conventionally attached to the motor shaft can be used. Speed control becomes possible.

〔Effect of the invention〕

As explained above, according to the present invention, the connection configuration between the electric motor and the Cerbius speed control device is improved, and a Cerbius speed control device with improved reliability can be provided.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a Servius speed control device according to an embodiment of the present invention, and FIG. 2 is a block diagram of a conventional Servius speed control device. 1...Winding type motor 2...Starting resistor 3.
...Converter 4...Inverter 5...Inverter transformer 8...Speed setter 9...Speed control circuit lO...Acceleration limiting circuit 11...Current control circuit 12...Current detector 13... Phase control circuit 14... Instrument transformer 15... Voltage detector 16... Instrument transformer 17... Voltage detector 18... Multiplier 19... Constant setter
20... Multiplier 21... Constant setter 22
...Divider 23...Converter agent Patent attorney Noriyuki Chika (and 1 other person) Figure 1

Claims (1)

[Claims] a converter connected to the secondary output side of the induction motor; an inverter connected in series to the converter and connected to the secondary side of an inverter transformer whose output side is connected to the input power supply side of the induction motor; A first voltage detector detects the secondary voltage of the induction motor, a second voltage detector detects the secondary voltage of the inverter transformer, and the output of the second voltage detector is connected to the inverter transformer. an arithmetic unit that calculates a secondary voltage when the induction motor is stopped by multiplying the turns ratio of the transformer and the turns ratio of the induction motor, and a slip value that divides the output of the first voltage detector by this secondary voltage. A Servius speed control device characterized in that it calculates the slip value and uses this slip value as a speed feedback signal.