CA1097403A - Alternating current variable speed motor-driven compressor system - Google Patents
Alternating current variable speed motor-driven compressor systemInfo
- Publication number
- CA1097403A CA1097403A CA301,050A CA301050A CA1097403A CA 1097403 A CA1097403 A CA 1097403A CA 301050 A CA301050 A CA 301050A CA 1097403 A CA1097403 A CA 1097403A
- Authority
- CA
- Canada
- Prior art keywords
- alternator
- field
- voltage
- motor combination
- current
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60H—ARRANGEMENTS OF HEATING, COOLING, VENTILATING OR OTHER AIR-TREATING DEVICES SPECIALLY ADAPTED FOR PASSENGER OR GOODS SPACES OF VEHICLES
- B60H1/00—Heating, cooling or ventilating [HVAC] devices
- B60H1/32—Cooling devices
- B60H1/3204—Cooling devices using compression
- B60H1/3222—Cooling devices using compression characterised by the compressor driving arrangements, e.g. clutches, transmissions or multiple drives
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P9/00—Arrangements for controlling electric generators for the purpose of obtaining a desired output
- H02P9/44—Control of frequency and voltage in predetermined relation, e.g. constant ratio
Landscapes
- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Mechanical Engineering (AREA)
- Power Engineering (AREA)
- Control Of Eletrric Generators (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
An alternating current motor-driven compressor for use in a refrigeration, air conditioning and/or heating system wherein the speed of the compressor is varied as a function of the frequency of the a.c. applied thereto, the a.c. power being generated in main alternator having an independent d.c. field supply providing limited increased field current during starting and predetermined field current during normal operation such that the output power from the alternator may be selected to accommodate the electrical demands thereon.
An alternating current motor-driven compressor for use in a refrigeration, air conditioning and/or heating system wherein the speed of the compressor is varied as a function of the frequency of the a.c. applied thereto, the a.c. power being generated in main alternator having an independent d.c. field supply providing limited increased field current during starting and predetermined field current during normal operation such that the output power from the alternator may be selected to accommodate the electrical demands thereon.
Description
~L~974(~,3 Electrical Control for a Refrigeration System This invention relates in general to truck refrigeration systems and more particularly to truck re-frigeration systems in which the compressor and fan motors are powered by an alternating electrical potential.
Most conventional truck electric powered refrigeration systems use a direct current electrical power system. The truck engine is used to mechanically drive an alternating current generator or alternator, and the output of the alternator is rectified to power direct current com-pressor and fan motors in the refrigeration system. In addition to the high cost of the rectifiers, which necessarily must be sized to handle all of the system power requirements direct current refrigeration systems require more maintenance and thus are out of service for longer periods of time. The brushes on the direct current motors are particularly subject to wear and must be frequently replaced.
It is, therefore, desirable to provide a truck 2Q refrigeration system in which only the alternator field winding and control elements require a direct current potential.
It is desirable for the compressor and fan motors to operate directly from the alternator output, thus eliminating motor brush maintenance and substantially reducing the size and cost of the rectifier elements. To operate the alternating potential motors at peak efficiency and constant line current, the electrical output of the alternator should desirably maintain ~ a constant voltage to frequency ratio. To further reduce i system cost and maintenance, the system should function with-out current transformer or ield rectifier and consideration should be given to energy saving.
A previous patent (See U.S.P. 3,283,525), which has had limited commercial success taught a system in which ~:.
`` 1~9~7403 the truck battery only assists in supplying excitation potential to the alternator field winding when the direct current potential provided by field rectifiers falls below a predetermined magnitude.
One embodiment of the invention described in U.~.
Patent 3,283,525 maintains the field excitation current pro-portional to the alternating current load, and maintains a nearly constant voltage to frequency ratio, and achieves this with only two current transformers instead of the conventional three. The primary windings of the current transformers are connected in series with two of the load conductors, and the secondary windings each have one end connected in common to one of the input terminals of a three phase full wave field rectifier, and the remaining ends of the secondary wind-ings are each connected to a different input terminal of the three phase field rectifier. Another embodiment of the invention described in U.S. P. 3,2133,525 maintains the field excitation current proportional to the load and maintains an alternator output having a nearly constant voltage to frequency ratio and achieves this with only one current transformer.
The primary winding of the single current transformer is connected in series with one of the load conductors, and the secondary winding of the current transformer is connected to two of the alternating current input terminals of the three phase, full wave field rectifier. Still another embodiment of the invention described in U.S. P. No. 3,283,525 completely eliminates the use of current transformers and still maintains an alternator output having a nearly constant voltage to frequency ratio, by connecting the field rectifier in the neutral of the alternator armature windings and using the - truck battery to provide excitation at light and no loads conditions.
! -2-1~974~3 In all the above mentioned methods of field excitation, the current supplied to the field winding is directly proportional to the load current. Due to the motorized nature of the load being driven, (Compressor and fan motors) under normal running conditions the capacity of the refrigeration system and the alternator voltage vary in direct proportion to the truck engine speed while the current to the field winding remains fairly constant.
During motor start-up, in aforementioned embodiments, current supplied to the~field winding is increased inherently to maintain the alternator output voltage at a constant level. During motor start-up, the above mentioned technique is desirable when dealing with commercial network power distribution where fluctuation in voltage due to motor start-up load might affect other equipment such as lighting, electronic equipment, etc. connected on the same network.
But it is a known fact in the indu~;try that this method of motor starting, called "across the line starting", is more energy demanding and places ~ore stress on the motors and drive members.
Accordingly, it is an object of this invention to provide a new and improved refrigeration system.
Another object of the invention is to provide a new and improved refrigeration system in which the compressor and fan motors operate directly from the output of the ~`~ alternating current generator without requiring conversion to a direct current potential.
A further object of the invention is to provide a new and improved refrigeration system wherein an alternating potential having a constant voltage-to-frequency ratio for operation of alternating current motors is produced.
Another object of the invention is to provide a 974~)3 new and improved refrigeration system wherein reduced starting voltage for the motors forming part of the system is produced automatically.
A further object of the invention is to provide a new and improved refrigeration system in which an associated battery and a low voltage alternator are the sole sources of power for supplying excitation potential to the alternator winding thus assuring a constant ratio of voltage-to-frequency that varies with the load.
Another object of the invention is to provide a new and improved refrigeration system that is powered by an alternator that is capable of supplying full load current with a field excitation voltage less than an associated DC system for example, 12 or 24 volts DC available in a vehicle.
To simplify this description, controls that are known to the trade such as Cooling-Defrost and heating controls under and over voltage protection, over current protection, standby power etc., will not be dealt with.
A preferred embodiment of the invention will now be described with reference to the accompanying drawing which shows a circuit for an alternator-motor combination.
One embodiment of this invention maintains a `~ constant predetermined field excitation current to the power alternator. The above mentioned current is supplied by a secondary 12 volts or 24 volts alternator which may or may not form part of the vehicle DC system, through a standard vehicle type rectifier and voltage regulator control unit and a predetermined field resistor.
Another embodiment of this invention provides automatic reduced starting voltage for motors, forming part of the refrigeration system, by maintaining constant field excitation current instead of a field excitation current which ~io C~4(~3 is proportional to the load. Another embodiment of this in-vention provides a predetermined limit in the voltage drop upon motor starting by~momentarily increasing the field excitation upon motor start-up.
Another embodiment of this invention completely eliminates the use of a current transformer and field rectifier but which maintains an alternator output having a fairly and quite acceptable voltage to frequency ratio. Still another el~odiment of this invention is the use of a power alternator that can be driven to full load with a field excitation voltage less than the vehicle DC system, for example + 8 volts excitation current for a 12 volts DC vehicle system.
Since the refrigeration system capacity and, by the same token, the demand on the output of the power alternator is proportional to the truck engine speed when alternating current compressor and fan motors are used, if a constant excitation current is applied to the field it can be found that the current at the output of the alternator will remain constant for a given ` condition and that both the frequency and voltage will vary in direct proportion. As shown hereinafter, when not considering the motor start-up condition and by careful examination of different duty cycles it is found that only a few conditions of load variation exist on a refrigeration system which can be -` dealt with separately.
A) Cycle #1 Cooling: Compressor motor running and with two fractional horse-power fan motors runningO Full load condition.
B) Cycle ~2 No Cooling: Only one or two fractional horse power fan motors running. Light load condition.
C~ Cycle ~3 Hot Gas Defrost: Compressor motor running and one fractional horse-power fan running. Full load condition.
.: . - : .:
74~3 D) Cycle #4 Heating: Electric heating elements of approximately the same capacity as the compressor electrical load in operation and one fractional horse-power fan running. Full load condition.
It may be seen from the above that the cycles No. 1, 3 and 4 exhibit approximately the same heavy loading condition and cycle No. 2 exhibits a light loading condition.
By the use of a multi-tap field resistor and an auxiliary contact on the compressor and heating element contactors, which form part of a normal refrigeration system, the field current can be predetermined to satisfy all of the above conditions.
Further objects and advantages of the invention will become apparent as the following description proceeds `- and features of novelty which characterize the invention will be pointed out in particularity in the claims annexed to and forming a part of the speciEicatiol~.
A preferred embodiment of the invention will now be described with reference to the accompanying drawing which ~` 20 shows a circuit diagx~m of a vehicle having a refrigeration alternator.
Referring to the drawing, there is illustrated a schematic diagram of a vehicle refrigeration electrical power system descriptive of the invention. More specifically, an alternator lO having armature phase windings 12, 14 and 16, and an excitation fi~ld winding 18, is connected to supply '~ electrical energy to electrical conductors, 22, 24 and 26.
The alternator lO may be mechanically driven by a suitable drive 20, such as being belted to the engine of a vehicle. The drive 20 may be of fixed ratio or of a variable speed type.
In order to provide a direct current potential ~or the field excitation winding 18 as well`as for the various l~g74~3 control functions, an auxiliary alternator 28 which may or may not form part of a vehicle DC system, having armature phase windings 42, 44, 46 and an excitation field winding 40, is connected to supply alternating current electrical energy via electrical conductors 30, 32, 34 to a standard type rectifier and voltage regulator control unit 48 which provides direct current potential, via conductor 36, for the field winding 40 of the auxiliary al~ernator 28 and also supplies electrical energy to the vehicle battery 52 through conductor 50.
Auxiliary alternator 28 may be mechanically driven by a suitable drive such as being belted to the truck engine. Auxiliary alternator 28 and the rectifier and/or voltage regulator control unit 48 may be integral within the same unit.
Direct current potent:ial for the field . excitation winding 18 is tapped to -the regulator's 48 output `i through co.nductor 54, field resistor 56 and depending on load conditions, through conductor 58 and auxiliary contact 72 upon motor start up, through conductor 60 and compressor ` 20 auxiliary contact 74 or heating elements auxiliary contact ~:` 76 for full load condition and through conductor 62 on light load condition and then through conductor 64 then back to .:
the regulator through ground conductors 68 and 70. It is to be ~; understood that the field resistor 56 may comprise other voltage-dropping means, for example, a solid state device or an electrolyte.
It should be understood that the number and ; configuration of the auxiliary contacts may vary depending on the components utilized in the refrigeration system.
An alternative method of varying the field current in the field winding 18 could be by providing the field winding ~9~03 18 with a plurality of taps, Switching means similar to 72, 74 and 76 could then ~e used for selecting taps appropriate to the desired field current.
':
`' .
, . ,
Most conventional truck electric powered refrigeration systems use a direct current electrical power system. The truck engine is used to mechanically drive an alternating current generator or alternator, and the output of the alternator is rectified to power direct current com-pressor and fan motors in the refrigeration system. In addition to the high cost of the rectifiers, which necessarily must be sized to handle all of the system power requirements direct current refrigeration systems require more maintenance and thus are out of service for longer periods of time. The brushes on the direct current motors are particularly subject to wear and must be frequently replaced.
It is, therefore, desirable to provide a truck 2Q refrigeration system in which only the alternator field winding and control elements require a direct current potential.
It is desirable for the compressor and fan motors to operate directly from the alternator output, thus eliminating motor brush maintenance and substantially reducing the size and cost of the rectifier elements. To operate the alternating potential motors at peak efficiency and constant line current, the electrical output of the alternator should desirably maintain ~ a constant voltage to frequency ratio. To further reduce i system cost and maintenance, the system should function with-out current transformer or ield rectifier and consideration should be given to energy saving.
A previous patent (See U.S.P. 3,283,525), which has had limited commercial success taught a system in which ~:.
`` 1~9~7403 the truck battery only assists in supplying excitation potential to the alternator field winding when the direct current potential provided by field rectifiers falls below a predetermined magnitude.
One embodiment of the invention described in U.~.
Patent 3,283,525 maintains the field excitation current pro-portional to the alternating current load, and maintains a nearly constant voltage to frequency ratio, and achieves this with only two current transformers instead of the conventional three. The primary windings of the current transformers are connected in series with two of the load conductors, and the secondary windings each have one end connected in common to one of the input terminals of a three phase full wave field rectifier, and the remaining ends of the secondary wind-ings are each connected to a different input terminal of the three phase field rectifier. Another embodiment of the invention described in U.S. P. 3,2133,525 maintains the field excitation current proportional to the load and maintains an alternator output having a nearly constant voltage to frequency ratio and achieves this with only one current transformer.
The primary winding of the single current transformer is connected in series with one of the load conductors, and the secondary winding of the current transformer is connected to two of the alternating current input terminals of the three phase, full wave field rectifier. Still another embodiment of the invention described in U.S. P. No. 3,283,525 completely eliminates the use of current transformers and still maintains an alternator output having a nearly constant voltage to frequency ratio, by connecting the field rectifier in the neutral of the alternator armature windings and using the - truck battery to provide excitation at light and no loads conditions.
! -2-1~974~3 In all the above mentioned methods of field excitation, the current supplied to the field winding is directly proportional to the load current. Due to the motorized nature of the load being driven, (Compressor and fan motors) under normal running conditions the capacity of the refrigeration system and the alternator voltage vary in direct proportion to the truck engine speed while the current to the field winding remains fairly constant.
During motor start-up, in aforementioned embodiments, current supplied to the~field winding is increased inherently to maintain the alternator output voltage at a constant level. During motor start-up, the above mentioned technique is desirable when dealing with commercial network power distribution where fluctuation in voltage due to motor start-up load might affect other equipment such as lighting, electronic equipment, etc. connected on the same network.
But it is a known fact in the indu~;try that this method of motor starting, called "across the line starting", is more energy demanding and places ~ore stress on the motors and drive members.
Accordingly, it is an object of this invention to provide a new and improved refrigeration system.
Another object of the invention is to provide a new and improved refrigeration system in which the compressor and fan motors operate directly from the output of the ~`~ alternating current generator without requiring conversion to a direct current potential.
A further object of the invention is to provide a new and improved refrigeration system wherein an alternating potential having a constant voltage-to-frequency ratio for operation of alternating current motors is produced.
Another object of the invention is to provide a 974~)3 new and improved refrigeration system wherein reduced starting voltage for the motors forming part of the system is produced automatically.
A further object of the invention is to provide a new and improved refrigeration system in which an associated battery and a low voltage alternator are the sole sources of power for supplying excitation potential to the alternator winding thus assuring a constant ratio of voltage-to-frequency that varies with the load.
Another object of the invention is to provide a new and improved refrigeration system that is powered by an alternator that is capable of supplying full load current with a field excitation voltage less than an associated DC system for example, 12 or 24 volts DC available in a vehicle.
To simplify this description, controls that are known to the trade such as Cooling-Defrost and heating controls under and over voltage protection, over current protection, standby power etc., will not be dealt with.
A preferred embodiment of the invention will now be described with reference to the accompanying drawing which shows a circuit for an alternator-motor combination.
One embodiment of this invention maintains a `~ constant predetermined field excitation current to the power alternator. The above mentioned current is supplied by a secondary 12 volts or 24 volts alternator which may or may not form part of the vehicle DC system, through a standard vehicle type rectifier and voltage regulator control unit and a predetermined field resistor.
Another embodiment of this invention provides automatic reduced starting voltage for motors, forming part of the refrigeration system, by maintaining constant field excitation current instead of a field excitation current which ~io C~4(~3 is proportional to the load. Another embodiment of this in-vention provides a predetermined limit in the voltage drop upon motor starting by~momentarily increasing the field excitation upon motor start-up.
Another embodiment of this invention completely eliminates the use of a current transformer and field rectifier but which maintains an alternator output having a fairly and quite acceptable voltage to frequency ratio. Still another el~odiment of this invention is the use of a power alternator that can be driven to full load with a field excitation voltage less than the vehicle DC system, for example + 8 volts excitation current for a 12 volts DC vehicle system.
Since the refrigeration system capacity and, by the same token, the demand on the output of the power alternator is proportional to the truck engine speed when alternating current compressor and fan motors are used, if a constant excitation current is applied to the field it can be found that the current at the output of the alternator will remain constant for a given ` condition and that both the frequency and voltage will vary in direct proportion. As shown hereinafter, when not considering the motor start-up condition and by careful examination of different duty cycles it is found that only a few conditions of load variation exist on a refrigeration system which can be -` dealt with separately.
A) Cycle #1 Cooling: Compressor motor running and with two fractional horse-power fan motors runningO Full load condition.
B) Cycle ~2 No Cooling: Only one or two fractional horse power fan motors running. Light load condition.
C~ Cycle ~3 Hot Gas Defrost: Compressor motor running and one fractional horse-power fan running. Full load condition.
.: . - : .:
74~3 D) Cycle #4 Heating: Electric heating elements of approximately the same capacity as the compressor electrical load in operation and one fractional horse-power fan running. Full load condition.
It may be seen from the above that the cycles No. 1, 3 and 4 exhibit approximately the same heavy loading condition and cycle No. 2 exhibits a light loading condition.
By the use of a multi-tap field resistor and an auxiliary contact on the compressor and heating element contactors, which form part of a normal refrigeration system, the field current can be predetermined to satisfy all of the above conditions.
Further objects and advantages of the invention will become apparent as the following description proceeds `- and features of novelty which characterize the invention will be pointed out in particularity in the claims annexed to and forming a part of the speciEicatiol~.
A preferred embodiment of the invention will now be described with reference to the accompanying drawing which ~` 20 shows a circuit diagx~m of a vehicle having a refrigeration alternator.
Referring to the drawing, there is illustrated a schematic diagram of a vehicle refrigeration electrical power system descriptive of the invention. More specifically, an alternator lO having armature phase windings 12, 14 and 16, and an excitation fi~ld winding 18, is connected to supply '~ electrical energy to electrical conductors, 22, 24 and 26.
The alternator lO may be mechanically driven by a suitable drive 20, such as being belted to the engine of a vehicle. The drive 20 may be of fixed ratio or of a variable speed type.
In order to provide a direct current potential ~or the field excitation winding 18 as well`as for the various l~g74~3 control functions, an auxiliary alternator 28 which may or may not form part of a vehicle DC system, having armature phase windings 42, 44, 46 and an excitation field winding 40, is connected to supply alternating current electrical energy via electrical conductors 30, 32, 34 to a standard type rectifier and voltage regulator control unit 48 which provides direct current potential, via conductor 36, for the field winding 40 of the auxiliary al~ernator 28 and also supplies electrical energy to the vehicle battery 52 through conductor 50.
Auxiliary alternator 28 may be mechanically driven by a suitable drive such as being belted to the truck engine. Auxiliary alternator 28 and the rectifier and/or voltage regulator control unit 48 may be integral within the same unit.
Direct current potent:ial for the field . excitation winding 18 is tapped to -the regulator's 48 output `i through co.nductor 54, field resistor 56 and depending on load conditions, through conductor 58 and auxiliary contact 72 upon motor start up, through conductor 60 and compressor ` 20 auxiliary contact 74 or heating elements auxiliary contact ~:` 76 for full load condition and through conductor 62 on light load condition and then through conductor 64 then back to .:
the regulator through ground conductors 68 and 70. It is to be ~; understood that the field resistor 56 may comprise other voltage-dropping means, for example, a solid state device or an electrolyte.
It should be understood that the number and ; configuration of the auxiliary contacts may vary depending on the components utilized in the refrigeration system.
An alternative method of varying the field current in the field winding 18 could be by providing the field winding ~9~03 18 with a plurality of taps, Switching means similar to 72, 74 and 76 could then ~e used for selecting taps appropriate to the desired field current.
':
`' .
, . ,
Claims (7)
1. An alternator-motor combination for driving at least a compressor, said combination comprising:
i) an alternator having electrical output terminals and a field winding having separate field terminals, said alternator having a substantially constant voltage-to-frequency relationship;
(ii) driving means for driving said alternator that may vary in driving speed, (iii) an AC motor in driving engagement with said compressor, and (iv) field supply means for supplying direct field current to said separate field terminals, said field supply means providing:
(a) a predetermined starting field current which is substantially constant and whose value is selected to reduce the output voltage of said alternator during starting, and (b) a plurality of predetermined running field currents, each of one of said plurality of field currents provided a different selected output power from said alternator.
i) an alternator having electrical output terminals and a field winding having separate field terminals, said alternator having a substantially constant voltage-to-frequency relationship;
(ii) driving means for driving said alternator that may vary in driving speed, (iii) an AC motor in driving engagement with said compressor, and (iv) field supply means for supplying direct field current to said separate field terminals, said field supply means providing:
(a) a predetermined starting field current which is substantially constant and whose value is selected to reduce the output voltage of said alternator during starting, and (b) a plurality of predetermined running field currents, each of one of said plurality of field currents provided a different selected output power from said alternator.
2. An alternator-motor combination as in Claim 1 wherein said plurality of predetermined and substantially constant field currents is obtained from an independent constant voltage d.c. source via voltage dropping means.
3. An alternator-motor combination as in Claim 1 wherein said voltage dropping means is a tapped resistor.
4. An alternator-motor combination as in Claim 3 wherein said voltage dropping means is a solid state device.
5. An alternator-motor combination as in Claim 1 wherein said field supply means is electrically connected via selected pairs of a plurality of taps on said field winding.
6. An alternator-motor combination as in Claim 2 wherein said independent constant d.c. voltage source is a voltage regulator associated with an auxiliary power generating means.
7. An alternator-motor combination as in Claim 6 where said auxiliary power generating means is an alternator and includes rectifying means.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA301,050A CA1097403A (en) | 1978-04-13 | 1978-04-13 | Alternating current variable speed motor-driven compressor system |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA301,050A CA1097403A (en) | 1978-04-13 | 1978-04-13 | Alternating current variable speed motor-driven compressor system |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1097403A true CA1097403A (en) | 1981-03-10 |
Family
ID=4111224
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA301,050A Expired CA1097403A (en) | 1978-04-13 | 1978-04-13 | Alternating current variable speed motor-driven compressor system |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1097403A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5296799A (en) * | 1992-09-29 | 1994-03-22 | Davis Emsley A | Electric power system |
| US10823484B2 (en) | 2016-05-03 | 2020-11-03 | Carrier Corporation | Intelligent voltage control for electric heat and defrost in transport refrigeration system |
-
1978
- 1978-04-13 CA CA301,050A patent/CA1097403A/en not_active Expired
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5296799A (en) * | 1992-09-29 | 1994-03-22 | Davis Emsley A | Electric power system |
| US10823484B2 (en) | 2016-05-03 | 2020-11-03 | Carrier Corporation | Intelligent voltage control for electric heat and defrost in transport refrigeration system |
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| MKEX | Expiry |