CA1203006A - Starter for an electric motor and process for its operation - Google Patents
Starter for an electric motor and process for its operationInfo
- Publication number
- CA1203006A CA1203006A CA000424167A CA424167A CA1203006A CA 1203006 A CA1203006 A CA 1203006A CA 000424167 A CA000424167 A CA 000424167A CA 424167 A CA424167 A CA 424167A CA 1203006 A CA1203006 A CA 1203006A
- Authority
- CA
- Canada
- Prior art keywords
- resistors
- starter
- switches
- starting
- combinations
- 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
Landscapes
- Motor And Converter Starters (AREA)
Abstract
A b s t r a c t The invention relates to a starter for an electric motor with n resistors arranged in each phase of the motor, whereby n is an integer. By switches and a controller 2n combinations of resistors can be switched in series with the motor. For starting the motor at most 2n combinations are sequentially switched on, arranged according to decreasing resistance value. The on time of the combinations is preselected for attaining a pre-determined characteristic curve of current increase. With a starter according to this invention the individual resistors can be of relatively low load capacity and therefore small and electric motors even under heavy load can be started without heavy current surges and in finely spaced steps.
Description
~t3L)~)6 Starter for an electric motor and process or its operation This invention relates to a starter for an electric motor having n starting resistors and a plurality of controllable switches in each phase of the electric motor, whereby n is an integer, and having means for con-trolling the switches.
The invention further relates to a process for the operation of such a starter.
After switch-on and during the start of an electric motor, current has to be limited. As unequally loaded high power electric motors are increasingly in common usage, e.g. with compressors for heat pumps and air conditioners, the probLem of starting such electric motors under full load, without causing distur~ing voltage drops on the electric supply lines by the high starting current, is more and more common.
Known are phase control circuits which, however, need many and expensive interference suppressor means due to their generating of energetic high frequency parasitic waves which may be only allowed on the supply lines if sufficiently damped. A widespread use of such phase con-i2~3006 trol circuits is therefore not desirable for reasons of interference elimination.
Starters with star delta switches produce a short standstill of the electric motor while switching from star to delta when used with highly loaded motors (e.g. with a compressor with its piston at top dead cen-ter), therefore leading to a strong current surge when switching to delta configuration.
Starters with resistors do not exhibit these disadvantages. In starters known in the art making use of resistors arranged in parallel or in series the re-sistors are switched on individually. Each resistor there-fore has to dissipate high power losses during a relatively long time and has to be dimensioned accordingly. There-fore large sized resistors or blower-cooled resistors have to be used. Such arrangements are space consuming and expensive. The current increases in as many steps as resistors are used, usually leading to very coarsely spaced steps.
The object of the present invention is to provide a starter without the disadvantages of the prior art de-vices. In order to implement this object the invention is characterized in that the control inputs of said
The invention further relates to a process for the operation of such a starter.
After switch-on and during the start of an electric motor, current has to be limited. As unequally loaded high power electric motors are increasingly in common usage, e.g. with compressors for heat pumps and air conditioners, the probLem of starting such electric motors under full load, without causing distur~ing voltage drops on the electric supply lines by the high starting current, is more and more common.
Known are phase control circuits which, however, need many and expensive interference suppressor means due to their generating of energetic high frequency parasitic waves which may be only allowed on the supply lines if sufficiently damped. A widespread use of such phase con-i2~3006 trol circuits is therefore not desirable for reasons of interference elimination.
Starters with star delta switches produce a short standstill of the electric motor while switching from star to delta when used with highly loaded motors (e.g. with a compressor with its piston at top dead cen-ter), therefore leading to a strong current surge when switching to delta configuration.
Starters with resistors do not exhibit these disadvantages. In starters known in the art making use of resistors arranged in parallel or in series the re-sistors are switched on individually. Each resistor there-fore has to dissipate high power losses during a relatively long time and has to be dimensioned accordingly. There-fore large sized resistors or blower-cooled resistors have to be used. Such arrangements are space consuming and expensive. The current increases in as many steps as resistors are used, usually leading to very coarsely spaced steps.
The object of the present invention is to provide a starter without the disadvantages of the prior art de-vices. In order to implement this object the invention is characterized in that the control inputs of said
- 2 --.~, ~Z~3006 switches are connected to the outputs of said controlling means and further characterized in that said controlling means are able to generate control signals for said switches whereby all possible 2n combinations of said starting resistors can be switched in predetermined sequence in series with said electric motor.
A further object of the invention is to provide a process for the operation of a starter as described in the main claim. In order to implement this object the in-~ vention is characterized in that for starting said elec-tric motor said starting resistors are switched on or off, respectively, individually and in groups, for increasing the starting current in 2n steps at most, whereby the duration of the time of each combination of said resistors is preselected to attain a predetermined characteristic curve of increase of said starting current.
By switching the resistors on or off, respective-ly, the losses o individual resistors regarding current and time are reduced, allowing the use of substantially smaller ~;rPn~ioned resistors. Moreover, the current increases in finer spaced steps and a preselected charac-teristic curve o increase can be easily attained.
A special embodiment of the invention is charac-terized in that the resistors are arranged in parallel.
iZ~)30~1~
A further special embodiment comprises five resistors having a resistance ratio of 1 : 2 : 4 8 : 16.
A special embodiment of the process for the operation is characterized in that all 32 possible resistance combinations using five resistors are sequen-tially switched on and off and arranyed according to de-creasing resistance value of the combinations.
A further special embodimènt of the process is characterized in that the duration of the on time of each - combination of resistors is selected as to attain an approximately linear increase of the motor current.
~ special embodiment of the invention is described by reference of the following detailed ~ r;rtion and the figures, wherein Fig. 1 is a baslc circuit diagram of a starter with four resistors;
Fig. 2 is a block diagram of a switch controller for the starter of Fig. l;
Fig. 3a is a resistance-time diagram of the starter of Fig. l;
Fig. 3b is another resistance-time diagram.
- Fig. 1 shows a basic circuit diagram of a starter with four resistors 1 - 4 arranged in parallel and 12~)300~;
connected via their irst connections, lead ll and termi-nal lO with the supply. Switches 5 - 8 connect the second connections of corresponding resistors and line 14 when in their on state. The electric motor (not shown~ is connected with terminal 13 of line 14. Such an array of switches and resistors has to be arranged in each phase of the electric motor but is shown here only once. After starting of the motor switch 12 makes a direct connection between the motor and the supply line and thence by-passes the switches 5 - 8 and resistors 1 - 4 of the starter. Switch 12 is usually a mechanic circuit breaker and works generally independently from the starter, e.g.
as a time controlled switch. Preferably, however, it can also be controlled by controller 9 as shown in Fig. 1.
The outputs A - D of controller 9 are connected to the control inputs of the switches 5 - 8 which are normal commercially available semiconductor switching devices, e.g. transistors, power FET's, triacs or others.
~ach output of controller 9 has two logical states, a high potential at the output will be denoted "1" and the corresponding switch is on (the contact is closed), a low potential at the output is denoted "O" and the cor-~responding switch is off (the contact is open). For '', ~
.
~Z~3C~O~
starting the motor the controller 9 is able to generate all possible combinations of switch contact combinations to provide a current limited starting and low losses on the resistors 1 - 4. `7 If the resistors 1 to 4 are selected as 25 ohm, 50 ohm, 100 ohm and 200 ohm, the following (rounded) resistance values correspond to the shown states of the outputs A - D:
Outputs A B C D Resistance value ~ohm~
O O O O ( oo ) 0 l 0 0 . 50 .
1 l 0 l 15 l 1 1 0 14 l l 1 1 13 With four resistors there are 16 resistance combinations available.
The main advantage of switching the resistors on and off is in sharing the losses among the resistors. It .
i~)31:)1)6 is therefore for example possible to start a 15 kW electric motor with a special embodiment of the starter having five 50 W resistors in each phase.
After reaching the lowest resistance value of -13 ohm or the output 1 1 1 1 of the controller respectively, the switch 12 is closed for connecting the started motor directly with the supply and the switches 5 - 8 are brought into their off state (contacts open)`. For controlling the resistance value and thereby the current increase over time the duration of the on time of individual resistance combinations can be preselected differently.
For generating the control signals for the switches 5 - 8 and switch 12 a commercially available logic pattern generator can be used. Fig. 2, however, shows a simple basic circuit for generating the control signals which can, for example, be built using readily available TTL-logic devices. A clock generator 20 y~a~es a square wave signal of constant frequency whereby the stabiliky of frequency thereo needs not to be very high and which signal is fed to a divider 21 with variable dividing ratio, a controller circuit 22 and from there to the clock input of a 4 bit counter 23.
The four outputs A - D of the counter provide 1;203~()6 the control signals for the switches 5 - 8. A star~
signal fed to the S input of controller circuit 22 lets the clock signal from divider 21 pass circuit 22, and therefore counter 23 begins to count, starting at its cleared state (outputs 0 0 0 0), forcing the outputs of counter 23 to go through all sixteen states (switch posi-tions or resistance combinations, respectively). By decoding of the counter outputs ~, ~, which change their state every four clock pulses (from 00 to 01 to 10 and 11 at last) the variable ratio divider is controlled, therefore giving four different clock rates reaching the counter. By this four groups of resistance combinations with different on time durations are formed. When the highest state of the counter 1 1 1 1 is reached, this state will be sensed by decoder 24 which applies a logic 1 signal to t~r~; n~l 25 for controlling switch 12. This logic 1 signal is further fed to the control circuit 22 for delaying the next clock pulse reaching the counter, therefore ensuring that switch 12 has enough time to close its contacts. The delayed clock pulse then generates the state 0 0 0 0 of the counter as well as a carry signal on the carry output Cy thereof. This carry signal is also fed to the control circuit 22 which then blocks the clock signal until the next start signal is applied to the S
,. .
' . . : : ' :
:~20300~
input of circuit 22.
Figs. 3a,b show resistance-time diagra~s for a special embodiment with four resistors of 25, 50, 100 and 200 ohms. The curve of Fig. 3a is an example with the same duration of the on time for all resistance com-binations. The curve of Fig. 3b on the contrary shows an example with different on time duration of resistance combinations.
.~
A further object of the invention is to provide a process for the operation of a starter as described in the main claim. In order to implement this object the in-~ vention is characterized in that for starting said elec-tric motor said starting resistors are switched on or off, respectively, individually and in groups, for increasing the starting current in 2n steps at most, whereby the duration of the time of each combination of said resistors is preselected to attain a predetermined characteristic curve of increase of said starting current.
By switching the resistors on or off, respective-ly, the losses o individual resistors regarding current and time are reduced, allowing the use of substantially smaller ~;rPn~ioned resistors. Moreover, the current increases in finer spaced steps and a preselected charac-teristic curve o increase can be easily attained.
A special embodiment of the invention is charac-terized in that the resistors are arranged in parallel.
iZ~)30~1~
A further special embodiment comprises five resistors having a resistance ratio of 1 : 2 : 4 8 : 16.
A special embodiment of the process for the operation is characterized in that all 32 possible resistance combinations using five resistors are sequen-tially switched on and off and arranyed according to de-creasing resistance value of the combinations.
A further special embodimènt of the process is characterized in that the duration of the on time of each - combination of resistors is selected as to attain an approximately linear increase of the motor current.
~ special embodiment of the invention is described by reference of the following detailed ~ r;rtion and the figures, wherein Fig. 1 is a baslc circuit diagram of a starter with four resistors;
Fig. 2 is a block diagram of a switch controller for the starter of Fig. l;
Fig. 3a is a resistance-time diagram of the starter of Fig. l;
Fig. 3b is another resistance-time diagram.
- Fig. 1 shows a basic circuit diagram of a starter with four resistors 1 - 4 arranged in parallel and 12~)300~;
connected via their irst connections, lead ll and termi-nal lO with the supply. Switches 5 - 8 connect the second connections of corresponding resistors and line 14 when in their on state. The electric motor (not shown~ is connected with terminal 13 of line 14. Such an array of switches and resistors has to be arranged in each phase of the electric motor but is shown here only once. After starting of the motor switch 12 makes a direct connection between the motor and the supply line and thence by-passes the switches 5 - 8 and resistors 1 - 4 of the starter. Switch 12 is usually a mechanic circuit breaker and works generally independently from the starter, e.g.
as a time controlled switch. Preferably, however, it can also be controlled by controller 9 as shown in Fig. 1.
The outputs A - D of controller 9 are connected to the control inputs of the switches 5 - 8 which are normal commercially available semiconductor switching devices, e.g. transistors, power FET's, triacs or others.
~ach output of controller 9 has two logical states, a high potential at the output will be denoted "1" and the corresponding switch is on (the contact is closed), a low potential at the output is denoted "O" and the cor-~responding switch is off (the contact is open). For '', ~
.
~Z~3C~O~
starting the motor the controller 9 is able to generate all possible combinations of switch contact combinations to provide a current limited starting and low losses on the resistors 1 - 4. `7 If the resistors 1 to 4 are selected as 25 ohm, 50 ohm, 100 ohm and 200 ohm, the following (rounded) resistance values correspond to the shown states of the outputs A - D:
Outputs A B C D Resistance value ~ohm~
O O O O ( oo ) 0 l 0 0 . 50 .
1 l 0 l 15 l 1 1 0 14 l l 1 1 13 With four resistors there are 16 resistance combinations available.
The main advantage of switching the resistors on and off is in sharing the losses among the resistors. It .
i~)31:)1)6 is therefore for example possible to start a 15 kW electric motor with a special embodiment of the starter having five 50 W resistors in each phase.
After reaching the lowest resistance value of -13 ohm or the output 1 1 1 1 of the controller respectively, the switch 12 is closed for connecting the started motor directly with the supply and the switches 5 - 8 are brought into their off state (contacts open)`. For controlling the resistance value and thereby the current increase over time the duration of the on time of individual resistance combinations can be preselected differently.
For generating the control signals for the switches 5 - 8 and switch 12 a commercially available logic pattern generator can be used. Fig. 2, however, shows a simple basic circuit for generating the control signals which can, for example, be built using readily available TTL-logic devices. A clock generator 20 y~a~es a square wave signal of constant frequency whereby the stabiliky of frequency thereo needs not to be very high and which signal is fed to a divider 21 with variable dividing ratio, a controller circuit 22 and from there to the clock input of a 4 bit counter 23.
The four outputs A - D of the counter provide 1;203~()6 the control signals for the switches 5 - 8. A star~
signal fed to the S input of controller circuit 22 lets the clock signal from divider 21 pass circuit 22, and therefore counter 23 begins to count, starting at its cleared state (outputs 0 0 0 0), forcing the outputs of counter 23 to go through all sixteen states (switch posi-tions or resistance combinations, respectively). By decoding of the counter outputs ~, ~, which change their state every four clock pulses (from 00 to 01 to 10 and 11 at last) the variable ratio divider is controlled, therefore giving four different clock rates reaching the counter. By this four groups of resistance combinations with different on time durations are formed. When the highest state of the counter 1 1 1 1 is reached, this state will be sensed by decoder 24 which applies a logic 1 signal to t~r~; n~l 25 for controlling switch 12. This logic 1 signal is further fed to the control circuit 22 for delaying the next clock pulse reaching the counter, therefore ensuring that switch 12 has enough time to close its contacts. The delayed clock pulse then generates the state 0 0 0 0 of the counter as well as a carry signal on the carry output Cy thereof. This carry signal is also fed to the control circuit 22 which then blocks the clock signal until the next start signal is applied to the S
,. .
' . . : : ' :
:~20300~
input of circuit 22.
Figs. 3a,b show resistance-time diagra~s for a special embodiment with four resistors of 25, 50, 100 and 200 ohms. The curve of Fig. 3a is an example with the same duration of the on time for all resistance com-binations. The curve of Fig. 3b on the contrary shows an example with different on time duration of resistance combinations.
.~
Claims (11)
1. A starter for an electric motor having n starting resistors and a plurality of controllable switches in each phase of the electric motor, whereby n is an integer, and having means for controlling the switches, characterized in that the control inputs of said switches are connected to the outputs of said controlling means and further characterized in that said controlling means are able to generate control signals for said switches, whereby all possible 2n combinations of said starting resistors can be switched in predetermined sequence in series with said electric motor.
2. A started as described in claim 1, charac-terized in that said starting resistors are arranged in parallel connection.
3. A starter as described in claim 1, charac-terized in that said starting resistors have different resistance values.
4. A starter as described in claim 3, comprising five resistors having a resistance ratio of 1 : 2 : 4 :
8 : 16.
8 : 16.
5. A starter as described in claim 1, charac-terized in that said switches are semiconductor switches.
6. Starter as described in claim 1, charac-terized in that said controlling means are provided with logic circuit elements with binary output states.
7. Process for the operation of a starter as described in claim 1, characterized in that for starting said electric motor said starting resistors are switched on or off, respectively, individually and in groups, for increasing the starting current in 2n steps at most, whereby the duration of the on time of each combination of said resistors is preselected to attain a predetermined characteristic curve of increase of said starting current.
8. Process as described in claim 7, characterized in that said starting resistors comprise five resistors with a resistance ratio of 1 : 2 : 4 : 8 : 16, wherein all 25 combinations of said resistors are sequentially switched on arranged according to decreasing resistance value.
9. Process as described in claim 7, characterized in that said duration of the on time of said combinations of said resistors is preselected to attain an approxi-mately linear current increase.
10. Process as described in claim 9, charac-terized in that said combinations of said resistors are arranged in four groups, whereby in each group the dura-tion of the on time of said combinations equals each other but decreases from one group to the next.
11. A starter for an electric motor having at least one phase, said starter comprising a number of n starting resistors and a plurality of controllable switches for each said phase, each of said switches having a control input, and further comprising means for controlling said switches connected to said inputs and operative to generate control signals for said controllable switches,such as to switch all possible 2n combinations of said starting resistors successively in series to the motor in predetermined sequence. --
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CH2640/82-0 | 1982-04-30 | ||
| CH264082 | 1982-04-30 | ||
| CH23/83A CH659780A5 (en) | 1982-12-29 | 1983-01-04 | MAGNETIC STIRRER. |
| CH83/00023 | 1983-03-01 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1203006A true CA1203006A (en) | 1986-04-08 |
Family
ID=25683283
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000424167A Expired CA1203006A (en) | 1982-04-30 | 1983-03-22 | Starter for an electric motor and process for its operation |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1203006A (en) |
-
1983
- 1983-03-22 CA CA000424167A patent/CA1203006A/en not_active Expired
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US3670237A (en) | Apparatus for the smooth switching-on of an electrical load | |
| US3470436A (en) | Electrical control apparatus | |
| WO1998029788A1 (en) | Method and device for automatically switching three-phase voltage for power saving transformer | |
| US5455469A (en) | Comparator controlled delay-on-break devices | |
| CA1203006A (en) | Starter for an electric motor and process for its operation | |
| JPH10337063A (en) | Method and device for starting ac electric motor | |
| CA1147019A (en) | Motor energizing circuit including free-running diodes and demagnetization windings | |
| US3258668A (en) | Motor starter circuit | |
| US4695741A (en) | Switchgear | |
| US4250437A (en) | Field weakening circuits for electric motors | |
| US4447741A (en) | Base drive circuit for power transistors | |
| US3848168A (en) | Speed control system for a-c supplied universal motors | |
| JPS59501193A (en) | Electric motor starter and its working process | |
| JPH1127933A (en) | Method and device for controlling output of electric consumption body | |
| US4128791A (en) | Phase shift circuit for synchronous motor | |
| US3753044A (en) | Phase firing circuits | |
| RU1808165C (en) | Device for protection of excitation winding of synchronous electric machine | |
| GB2198895A (en) | Motor control circuit | |
| SU1118559A1 (en) | Device for remote control of printing machine members | |
| US5033107A (en) | Electric sauna heater | |
| US1479033A (en) | Motor controller | |
| US3337785A (en) | Synchronous motor starting system | |
| SU66062A1 (en) | Device for controlling two-motor electric drive | |
| SU1607054A1 (en) | Device for triggering pulsed source of secondary power supply | |
| SU1078567A1 (en) | Control device for three-phase asynchronous motor |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |