JPS5938437B2 - compressor protector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION In a compressor driven by a pole number switching motor, the present invention protects the compressor by a delay switch when the number of poles of the motor is switched, and also protects the compressor in the event of a failure of the delay switch. A protection device configured to perform the above protection is provided.

Conventionally, in a compressor driven by an electric motor that can switch the number of poles between two and four poles, when switching from two-pole operation to four-pole operation, inertia increases even though the motor has four-pole windings. For 4-pole synchronous speed (1800rpm)
The above rotation occurs, albeit for a short time.

At this time, excessive reverse braking torque is generated in the electric motor, and excessive stress is applied to the rotating shaft of the electric motor, which may cause damage.

Further, when switching from four-pole operation to two-pole operation, the power to the motor is stopped, albeit momentarily.

At this time, the balance between the motor torque and the load torque during two-pole operation may be lost, and the load torque may become large.

At this time, the electric motor would stop and become locked, which could result in burnout of the electric motor or damage to the sliding parts of the compressor.

In order to protect these, a method has been considered in which a delay timer is installed to stop the compressor for a certain period of time when the number of poles is changed, and then the number of poles is changed and the compressor is restarted. If the fixed delay operation could no longer be performed, the number of poles would be changed continuously as described above, which could cause damage to the compressor.

The present invention aims to improve these drawbacks, and will be described below with reference to the drawings showing one embodiment thereof.

1 is a three-phase induction motor, which is a pole switching motor that drives the compressor.The windings of each phase are connected in series to form a four-pole motor, and the windings of each phase are connected in parallel to form a two-pole motor. It becomes an electric motor.

The motor is connected to multi-pole terminals la and 1b via the contacts 3 of the 4-pole switch 2.

1o is connected to the power supply P, resulting in four-pole operation, and the small-pole terminal 1d is connected to the contact 5 of the two-pole switch 4.

1e and 1f are connected to the power supply P to perform two-pole operation.

6 is a phase advancing capacitor of pole number switching motor 1, and its power supply P
A contact 8 of the power switch 7 is provided on the side.

Reference numeral 9 denotes a control power supply applied to terminals 10 and 11, and terminal 10 is connected to a power switch 13 and a pole number switching switch 14 via an operation switch 12.

The power switch 13 is connected to a coil 15 that operates the power switch 7, controls the power switch 7, and is opened and closed manually or automatically by a thermostat or the like.

The pole number switching switch 14 is provided with a small-pole contact 16 and a multi-pole contact 17, and the respective contacts 16 and 17 are switched to open and close.

The small-pole contact 16 is connected to a coil 18 that operates the two-pole switch 4, and is also connected to a heater 20 that is a delay element of a small-pole delay switch 19.

Further, the coil 18 further includes the delay switch 19 for small poles.
The terminal 11 is connected to the terminal 11 via a normally open contact 21 .

Further, the small pole delay switch 19 is provided with a normally closed contact 22 .

The multi-pole contact 17 of the pole number switching switch 14 is connected to a coil 23 that operates the four-pole switch 2, and is also connected to a heater 25 which is a delay element of the multi-pole delay switch 24. .

Further, the coil 23 further includes the multi-pole delay switch 24.
The heater 25 is connected to the terminal 11 through the normally open contact 26 of the delay switch 19 for small poles, and the heater 20 is connected to the terminal 11 through the normally closed contact 22 of the delay switch 19 for small poles. terminal 11 via the normally closed contact 21 of the delay switch 24
It is connected to the.

Next, the operation will be explained.

If the operation switch 12 is closed and the small-pole contact 16 of the pole number changeover switch 14 is closed, the heater 20 of the small-pole delay switch 19 is energized, and after a certain delay, the normally closed contact 22 is closed. is opened, the normally open contact 21 is closed, the coil 18 is energized, the two-pole switch 4 is operated, and the motor 1 becomes a two-pole motor.

Next, when the power switch 13 is closed, the coil 15 is energized, the contact 8 of the power switch 7 is operated, and the motor 1 is operated with two poles.

Next, in order to switch the number of poles of the motor 1 from 2 to 4 poles, switch the pole number switching switch 14, open the small pole contact 16 and close the multi pole contact 17, and the 2 pole switch 4 The contact point 5 of is opened, power supply to the electric motor 1 is stopped, and the compressor is stopped.

Therefore, no reverse braking torque is generated in the electric motor 1.

After a certain delay, the delay mechanism (not shown) made of bimetal, etc. that was heated by the heater 20 during the two-pole operation of the eclipse delay switch 19 releases heat and cools down, and the normally open contact 21 opens and is normally closed. Contact 22 is closed.

As a result, the heater 25 of the multi-pole delay switch 24 is energized by the multi-pole contact 17 of the pole number switching switch 14, and after a certain period of time, the normally closed contact 27 is opened and the normally open contact 26
is closed, the coil 23 is energized, the 4-pole switch 2 is operated, and the motor is restarted with 4 poles.

The time between stopping 2-pole operation and starting 4-pole operation is short, but since the compressor is temporarily stopped, the differential pressure between the discharge side and suction side of the compressor decreases, and the starting load torque decreases. , it becomes possible to restart easily and reliably.

Next, during 4-pole operation, switch the pole number switching switch 14 again to open the multi-pole contact 17 and close the small-pole contact 16.
The contacts 3 of the 4-pole switch 2 are opened, the motor 1 is stopped, and after a certain delay as described above, the 4-pole delay switch 24 is opened.
A delay mechanism (not shown) made of a bimetal or the like that was heated by the heater 25 during the polar operation radiates heat and cools the normally open contact 26, and the normally closed contact 27 is closed.

As a result, the heater 20 of the small-pole delay switch 19 is energized, the constant delay wave normally open contact 21 is closed, the coil 18 is energized, and the two-pole switch 4 is activated, resulting in two-pole operation. .

Since the compressor is temporarily stopped when switching from four-pole operation to two-pole operation, it is possible to easily and reliably start the two-pole operation with a low starting load torque.

Next, a case where the delay switch 19 or 24 fails will be explained.

As an example, if the small pole delay switch 19 fails and the normally closed contact 22 is always closed, the normally open contact 21 will not close and two pole operation will not be performed, and the pole number switching switch 1
The 4-pole operation is performed only when the 4 multi-pole contacts 17 are closed.

At this time as well, when the four poles are started, the delay operation of the multipole delay switch 24 is performed, and the compressor is stopped for a certain period of time and then restarted.

Furthermore, if the normally open contact 21 of the delay switch 19 for small poles fails so that it is always closed, the normally closed contact 22 is always open, so the heater 25 of the delay switch 24 for multiple poles is not energized. The normally open contact 26 was never closed, the 4-pole switch 2 did not operate, and only the 2-pole switch 4 and the small-pole contact 16 of the pole number switching switch 14 were closed. It operates at times and operates with two poles.

As described above, since the small-pole delay switch 19 and the multi-pole delay switch 24 are interlocked with each other, even if one of them fails, the number of poles will not change continuously.

Although the delay switch described above uses a heater as its delay element, it may also be delayed by a motor, etc., or electronically.In short, if it is a device that switches the contact after a certain time delay It is clear that electronic contacts (contactless) may also be used.

Further, although a three-phase induction motor is shown as the above-mentioned pole number switching motor, other motors may be used, and the effect is particularly great in a motor with a low starting torque such as a single-phase motor.

Further, although the contacts are opened and closed by one two-pole switch and one four-pole switch, it is clear that a plurality of switches may be used.

Furthermore, although the pole number switching electric motor of this embodiment has been described as one that switches between two poles and four poles, it is clear that the motor that switches to other pole numbers may also be used.

As is clear from the above embodiments, the compressor protection device of the present invention includes an electric motor that drives the compressor, a multi-pole switch that energizes the motor as a multi-pole motor, and a small-pole switch that energizes the motor as a small-pole motor. A pole switch, a pole number switching switch, and a multi-pole delay switch or a small number of poles switching switch that energizes the multi-pole switch or the small number of poles switch after a certain delay in response to the pole number switching switch. The multi-pole contact and the small-pole contact of the pole number switching switch are connected to the series circuit of the coil of the multi-pole switch and the contact of the multi-pole delay switch, respectively. A heater, etc. that is connected to the series circuit of the coil of the small-pole delay switch and the contact of the small-pole delay switch, and causes the delay operation of the small-pole delay switch to be connected to the opposite contact of the contact of the multi-pole delay switch. A delay element such as a heater for delay operation of the multi-pole delay switch is connected to a contact opposite to the contact of the small-pole delay switch, and an interlock circuit is formed with both delay switches. The coil of the multi-pole switch, the coil of the multi-pole delay switch, and the coil of the small-pole switch connected to the multi-pole contact and the small-pole contact of the number-of-pole changeover switch, respectively. The circuit of the delay switch for use forms the same circuit, making it a simple circuit and making it easy to perform servicing.
When switching the number of poles, the compressor must be stopped once and then restarted, so that the compressor can be reliably restarted without causing any startup failures.In particular, the reverse braking torque that occurs when switching from low-pole operation to multi-pole operation is reduced. In addition to prolonging the life of the compressor, in the event that the delay switch malfunctions,
Since it is operated with only one number of poles, there is no possibility that the number of poles will change continuously and cause damage to the compressor.

[Brief explanation of drawings]

The drawing is an electrical circuit diagram of a compressor protection device showing one embodiment of the present invention. 1...Pole switching motor, 2...4-pole switch, 4...2-pole switch, 19...
・Delay switch for small poles, 24... Delay switch for multi poles.

Claims (1)

[Claims] 1. An electric motor that drives the compressor, a multi-pole switch that energizes this motor as a multi-pole motor, a small-pole switch that energizes the motor as a small-pole motor, a pole number switching switch, and this pole number switching switch. It has a multi-pole delay switch or a small-pole delay switch that responds to the switch and energizes the multi-pole switch or the small-pole switch after a certain delay; The contact for poles and the contact for small poles are connected to the series circuit of the coil of the multipole switch and the contact of the delay switch for multipole, respectively, and the contact of the coil of the small pole switch and the contact of the delay switch for small pole. A delay element such as a heater for delaying operation of the small-pole delay switch is connected to a series circuit, and a delay element such as a heater for delaying operation of the small-pole delay switch is connected to a reverse contact of the contact of the multi-pole delay switch. A protection device for a compressor, comprising connecting a delay element such as a heater for delaying operation of the multi-pole delay switch to the reverse contact of the multi-pole delay switch, and forming an interlock circuit with both delay switches.