JPH04248382A - Starter for a plurality of motors different in capacity - Google Patents

Abstract

PURPOSE:To make motor capacity and power source capacity small by starting a plurality of motors great in inertial moment and different in capacity with one inverter. CONSTITUTION:The capacity of an inverter 10 is determined by the capacity of the largest motor M1. Moreover, the starting characteristics of the inverter 10 is determined based on the relation between the capacity of the motors M3 and M4, where the inertial moment of the load to the capacity is the largest, and the load. When the start command of the motor M11 is input, the contact 1a for starting is closed to start the motor M1 with the inverter 10. When the start of the motor M1 is completed, the contact 1a for starting is opened to disconnect the motor M1 from the inverter 10, and the contact 3a for normal operation is closed to connect it to a commercial power source 14 and change it over to normal operation. Even if the start commands of the motors M2-M4 are input during the start of the motor M1, the contacts 1b-1d for starting and the contacts 3b-3d for normal operation do not close. The start of the motors M2-M4 also are performed similarly.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a starting device for a plurality of electric motors of different capacities, and particularly to a starting device suitable for a plurality of electric motors of different capacities whose loads have a large moment of inertia.

0002

[Prior Art] Various types of equipment, such as manufacturing equipment, often use multiple electric motors with different capacities. Conventionally, starting these multiple electric motors has been carried out by providing a starter for each electric motor. There is.

Furthermore, in this type of motor, the moment of inertia is often large even if the steady state of the load is small. In such cases, conventionally, the capacity of the motor has been increased or The motor is started by flowing a large current without connecting a protective relay or the like to the motor that is suitable for the steady-state load.

0004

However, when the capacity of the motor is increased compared to the load in a steady state, the capacity of the starter also becomes large, which increases the cost of these starters. And for a load with a small steady state and a large moment of inertia,
During steady operation, the load is small compared to the capacity of the motor, so it is uneconomical.

Furthermore, each electric motor requires a starter, which is uneconomical, and most conventional starters are voltage controlled, in which case a large current of about five times the rated current flows during starting. Therefore, the noise at the time of starting is large, and the life of the motor is shortened due to repeated starting and stopping. In particular, when starting a motor by passing a large current through it without connecting a protective relay or the like to a motor suitable for a steady-state load, problems caused by such a large current are significant.

For these reasons, in the past, it was not possible to start and stop the electric motor frequently, and the electric motor was often operated continuously for long periods of time, resulting in unnecessary power consumption and high running costs. was there.

An object of the present invention is to provide a starting device for a plurality of electric motors having different capacities, which solves all of the above problems.

[0008]

[Means for Solving the Problems] A starting device according to the present invention includes a switching circuit provided between one inverter, a plurality of electric motors having different capacities, the inverter and a commercial power line, and a switching circuit that switches each of the electric motors at the time of starting. A start control means is provided that connects to the inverter and controls the switching circuit so as to connect to the commercial power line after the start is completed,
The capacity of the inverter is determined based on the capacity of the largest motor, and the starting characteristics of the inverter are determined based on the relationship between the capacity of the motor and the load, which has the largest moment of inertia of the load relative to the capacity.

[0009]

[Operation] By means of the switching circuit and the starting control means, each electric motor is connected to the inverter and started by the inverter at the time of starting, and after the starting is completed, it is switched to the commercial power source and operated thereby. The capacity of the inverter is determined based on the capacity of the motor with the largest capacity, and the starting characteristics of the inverter are determined based on the relationship between the capacity of the motor with the largest moment of inertia of the load relative to capacity and the load.
A single inverter can start a plurality of electric motors of different capacities with a large load moment of inertia.

Since each electric motor is started by an inverter, each electric motor can have a capacity commensurate with its steady state load, and the capacity of the electric motor can be reduced. Further, the starting current can be reduced to 1.2 times or less of the rated current, and a large current does not flow during starting.

[0011]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows four electric motors (M1) (M2) (M
3) (M4) The overall schematic configuration of the starter device is shown, and FIG. 2 shows its main parts in detail.

The capacities of the four electric motors (M1) to (M4) and GD2 corresponding to the moment of inertia of the load are as follows. Note that the capacity of each electric motor (M1) to (M4) is determined by the load during steady operation.

[0014]
Capacity [kW] GD2 [kg・m2]
First electric motor (M1) 200
760 Second electric motor (M2) 160
145 Third electric motor (M3)
55 35
0 4th electric motor (M4)
55 350
The starting device includes an inverter (10), a switching circuit (11), and a starting control circuit (12) as starting control means.

[0015] The inverter (10) has a rated breaking current of 60
400V commercial power line (1) via 0A circuit breaker (13)
4) is connected to. This commercial power line (14) is connected to a 6600V power line (16) via a transformer (15). The capacity of the inverter (10) is determined in consideration of the capacity of the largest first electric motor (M1), 200 kW, and is 300 kVA. In addition, an inverter (10
) The starting characteristics of the switching circuit (1
1) are four starting electromagnetic switch contacts (starting contacts) (1a) (1b) (1c) (1d), starting overload relays (2a) (2b) (2c) (2d), Contact of electromagnetic switch for steady operation (contact for steady operation) (3a) (3
b) (3c) (3d), overload relay for steady operation (4a
) (4b) (4c) (4d) and circuit breakers (5a) (5
b) (5c) (5d). Each electric motor (M1) to (M4) is connected to a starting overload relay (2a) to (2d) and a starting contact (1a) to (1d), respectively.
) is connected to the inverter (10) via
Overload relays (4a) to (4d) for steady operation, contacts (3a) to (3d) for steady operation, and circuit breakers (5a) to (5
d) to the commercial power line (14).

The rated breaking current of the first and second circuit breakers (5a) (5b) is 600A, and the rated breaking current of the third and fourth circuit breakers (5c
)(5d) is 225A. In addition, the sensitivity of each overload relay (2a) to (2d) (4a) to (4d) is determined to match the rated current of the corresponding electric motor (M1) to (M4). ) ~ (M4
) is protected.

Although not shown, the starting control circuit (12)
includes the above-mentioned electromagnetic switch for starting, electromagnetic switch for steady operation, etc., including a manual start switch for starting each motor (M1) to (M4) individually, and a switch for starting the four motors (
An automatic start switch and the like for automatically starting M1) to (M4) are connected.

The starting control circuit (12) controls the electric motors (M1) to 1 by controlling the switching circuit (11) as follows.
(M4) is started.

[0019] From the manual start switch to the first motor (M1)
When the start command is input, the first start contact (1a
) is closed, and the first electric motor (M
1) Start. When the starting of the first electric motor (M1) is completed after a predetermined period of time has elapsed, the first starting contact (1a
) and connect the first motor (M1) to the inverter (10).
After about 3 seconds have elapsed to prevent the influence of residual voltage, the first steady operation contact (3a) is closed, and the first motor (M1) is connected to the commercial power line (14). Switch to steady operation. Note that an interlock is provided so that the first starting contact (1a) and the first steady operation contact (3a) do not close at the same time at this time. Also, while the first electric motor (M1) is starting, the second to fourth electric motors (M
2) An interface in which the 2nd to 4th starting contacts (1b) to (1d) and the 2nd to 4th steady operation contacts (3b) to (3d) do not close even if the starting commands from to (M4) are input. A lock is also provided.

The second to fourth electric motors (M2) to (M4) are started in the same manner. In addition, the four electric motors (M1) to (M4) are started in a predetermined order as described above by an automatic start command from an automatic start switch.

It should be noted that the configurations and numerical values of each part in the above embodiments are merely examples, and the present invention is not limited thereto.

[0022]

According to the starting device of the present invention, as described above, a plurality of electric motors with large moments of inertia and different capacities can be started with one inverter, and therefore the capacity of the electric motors and the power supply capacity can be reduced. This prevents large current from flowing during startup. Since no large current flows during starting, the noise caused by starting is significantly reduced, and the life of the motor will not be shortened even if starting and stopping are repeated. Therefore, the electric motor can be started and stopped as necessary, and running costs can be reduced.

[Brief explanation of the drawing]

FIG. 1 is an overall schematic block diagram of a starting device showing an embodiment of the present invention.

FIG. 2 is a circuit diagram showing main parts of FIG. 1;

[Explanation of symbols]

(M1) (M2) (M3) (M4) Electric motor (10)
Inverter (11)
Switching circuit (12)
Starting control circuit (starting control means)

Claims (1)

[Claims] [Claim 1] One inverter (10), a plurality of electric motors (M1) (M2) (M3) (M4) having different capacities, provided between the inverter (10) and the commercial power line (14). The switching circuit (11) and the electric motors (M1, M2, M3, and M4) are connected to the inverter (10) at the time of starting, and connected to the commercial power line (14) after the starting is completed. The electric motor (M1) (M2) is equipped with a starting control means (12) for controlling the circuit (11), and the inverter (10) has the largest capacity.
) (M3) (M4), and the starting characteristics of the inverter (10) are the motors (M1) (M2) (M3) with the largest moment of inertia of the load relative to the capacity.
) (M4) A starting device for a plurality of electric motors with different capacities determined based on the relationship between capacity and load.