CA1187930A - Circuit for controlling multiple rated motors - Google Patents
Circuit for controlling multiple rated motorsInfo
- Publication number
- CA1187930A CA1187930A CA000382419A CA382419A CA1187930A CA 1187930 A CA1187930 A CA 1187930A CA 000382419 A CA000382419 A CA 000382419A CA 382419 A CA382419 A CA 382419A CA 1187930 A CA1187930 A CA 1187930A
- Authority
- CA
- Canada
- Prior art keywords
- windings
- contactor
- torque
- delta
- motor
- 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
ABSTRACT OF THE DISCLOSURE
A circuit comprising a load sensor connected to a multiple rated motor for monitoring the motor load demand and a switching apparatus connected to the source of electrical power for charging the connection of elec-trical power to the windings of the motor under load in response to the motor load demand.
A circuit comprising a load sensor connected to a multiple rated motor for monitoring the motor load demand and a switching apparatus connected to the source of electrical power for charging the connection of elec-trical power to the windings of the motor under load in response to the motor load demand.
Description
~'7~ ~ ~
1 48,969 CIRCUIT FOR CONTROLLING MULTIPLE RATE~ MOTORS
BACKGROUND OF THE INVENTION
. . .
Field of the Invention:
.... _ .
This invention relates to control circuits used for controlling multiple rated motors where the applica-tion of the motor requires that the horsepower and torqueratings vary with time. Description of the Prior Art:
Multiple rated motors give~ the user a choice of operating modes 50 that the most effective operation can be obtained by loads that have variant horsepower and torque requirements during operation. ~s the ]oad demands vary with time conventional polyphase motors have proven to be less efficient and economical. A varying load can also put additional mechanical stress on the conventional polyphase motors. Mutliple rated motors give the user a motor whose speed torque characteristics c~n vary with the changing demand. However, sophisticated controls are required to shift the motor from one operating mode to another in accordance with the load conditions to attain the more economical and efficient operation.
A reference of interest is a paper entitled "Electric Motor Drives For Oil Well Walking Beam Pumps", written by R. F~ Woll, Fel]ow IEEE, Medium Motor Ancl Gearing Division, Westinghouse Electric Corporation, BuffaloJ N.Y. which is copyrighted material of the IEEE
and designated Conference Record 76 CH1109~8-lA, Paper No.
PC 1 7~-33.
~37~3~
1 48,969 CIRCUIT FOR CONTROLLING MULTIPLE RATE~ MOTORS
BACKGROUND OF THE INVENTION
. . .
Field of the Invention:
.... _ .
This invention relates to control circuits used for controlling multiple rated motors where the applica-tion of the motor requires that the horsepower and torqueratings vary with time. Description of the Prior Art:
Multiple rated motors give~ the user a choice of operating modes 50 that the most effective operation can be obtained by loads that have variant horsepower and torque requirements during operation. ~s the ]oad demands vary with time conventional polyphase motors have proven to be less efficient and economical. A varying load can also put additional mechanical stress on the conventional polyphase motors. Mutliple rated motors give the user a motor whose speed torque characteristics c~n vary with the changing demand. However, sophisticated controls are required to shift the motor from one operating mode to another in accordance with the load conditions to attain the more economical and efficient operation.
A reference of interest is a paper entitled "Electric Motor Drives For Oil Well Walking Beam Pumps", written by R. F~ Woll, Fel]ow IEEE, Medium Motor Ancl Gearing Division, Westinghouse Electric Corporation, BuffaloJ N.Y. which is copyrighted material of the IEEE
and designated Conference Record 76 CH1109~8-lA, Paper No.
PC 1 7~-33.
~37~3~
2 ~18,9~9 UMM~RY OF T_IE INVEN_ION
'~`hi.s ap-plication provicles an invention with a lo~1d sensing means connected to a multiple rated mvtor for moni.toring the motor load demand and a switching means connected to the source of electrical. power for changing t.he connection of electrical power to the windin~s of the motor under load in response to the motor ~oad demand.
I`his invention has par~icular application for use as an electric motor drive for oil well walking beam pumps where 0 the motor must have sufficient lock rotor torque for initial startup when lubricants in the overall pumping system may be cold and stiff. A fundamental purpose of t:he multiple rated motor is to afford a choice of operat-:ing modes 50 that the most effective operation can be attaitled from the motor on the particular beam pump it dr:ives. Th.is is accomplished by running the motor in the tor~ue 1no(le in which it can achieve ini.tial startup and i.n wh-ich its inherent thermal protection does not talce it off t.he line duri.ng operation. After initial stc1rtup it may be desirable to shift the pump into another torque mode to achieve maximum speed as the loading torque decreases.
BRIEF DESCRIPTION OF THE DRAWINGS
. ~
Figure l illustrates one embodiment of a control scheme for a triple rated motor in accordance with the principles o:E this invention.
Figures 2, 3 and 4 illustrate the winding con-nections for a triple rated mo-tor.
DESCRIPTION OF THE PREFERRED EMBODIM~NT
... . _ _ _ _ _ . _ _ Referring to Figures 2, 3 and 4 t:here is shown
'~`hi.s ap-plication provicles an invention with a lo~1d sensing means connected to a multiple rated mvtor for moni.toring the motor load demand and a switching means connected to the source of electrical. power for changing t.he connection of electrical power to the windin~s of the motor under load in response to the motor ~oad demand.
I`his invention has par~icular application for use as an electric motor drive for oil well walking beam pumps where 0 the motor must have sufficient lock rotor torque for initial startup when lubricants in the overall pumping system may be cold and stiff. A fundamental purpose of t:he multiple rated motor is to afford a choice of operat-:ing modes 50 that the most effective operation can be attaitled from the motor on the particular beam pump it dr:ives. Th.is is accomplished by running the motor in the tor~ue 1no(le in which it can achieve ini.tial startup and i.n wh-ich its inherent thermal protection does not talce it off t.he line duri.ng operation. After initial stc1rtup it may be desirable to shift the pump into another torque mode to achieve maximum speed as the loading torque decreases.
BRIEF DESCRIPTION OF THE DRAWINGS
. ~
Figure l illustrates one embodiment of a control scheme for a triple rated motor in accordance with the principles o:E this invention.
Figures 2, 3 and 4 illustrate the winding con-nections for a triple rated mo-tor.
DESCRIPTION OF THE PREFERRED EMBODIM~NT
... . _ _ _ _ _ . _ _ Referring to Figures 2, 3 and 4 t:here is shown
3~ the winding connections for the three operating modes for a triple rated motor controlled in accordance with ~he principles of this invention. Figure 2 shows the connec-tion for the high torque mode, Figure 3 the connection for -the medium torque mode, and Figure 4 the connection t-or t:he low torque mode. I`he torque owtput o~~ the ~ye low torque mode is one-third that of the delta high torque mode 3 the norma:l torque relationship between wye and de:lta connec-tion on a given motor. The torque output of the ~37~3~
3 ~8,969 medium torque connection depends upon how much of the motor wlnding is in the delta portion of the combination connection. Although Figure 3 shows half the motor wind-ing in the delta portion, more or less o~ the winding (wi.thin certain limitations) can be in the delta portion.
The more in the delta portion, the closer the medium torque output is to that of the full delta high torque connection; the less in the delta portion, the closer the medium torque output is to that of the plain wye load torque connection.
Figure 1 illustrates one embodiment of a control schematlc utilized for changing the motor terminal connec-tions for shifting from one torque mode to another.
Electrical power is connected to the line terminals Ll, L2 and L3 and passes through a conventional motor circuit breaker MCP or other circuit protection and disconnect devices. From the main circuit breaker MCP power passes through the contactor MC -to terminals Tl, T2 and T3. Con-nected to the load side of the contactor MC is a high mode contactor ~ which connects electrical power through three overloads to motor terminals T7, T8 and T9. Also connect-ed to the load side of the high mode contactor H is the medium mode contactor M which connects power to terminals T4, T5 and T6. Finally, a wye connection is connected to the load side of the high mode contactor H through an overload and parallel to the low mode contactor M. Con-trol power is supplied in a conventional manner by con-necting a step-down transformer to the line terminals Ll and L2. Control of the motor is initiated by first de-pressing the start pushbutton and completing the circuitXl, stop pushbutton, start pushbutton, the motor starter coil MC, the three overloads, H-OL, and X2. When the motor starter MC is energized, the contact MC-l closes and latches the start pushbutton in the start position and MC-2 closes and energizes the timer TDl by completing the circuit Xl, MC-2, TDl, and X2. At the same time MC-2 energizes the H contactor ~or the high torque mode b~
connecti.ng Xl, TDl-l, TDlA-l, M-l, L 1, H, and X2. At this 3~
3 ~8,969 medium torque connection depends upon how much of the motor wlnding is in the delta portion of the combination connection. Although Figure 3 shows half the motor wind-ing in the delta portion, more or less o~ the winding (wi.thin certain limitations) can be in the delta portion.
The more in the delta portion, the closer the medium torque output is to that of the full delta high torque connection; the less in the delta portion, the closer the medium torque output is to that of the plain wye load torque connection.
Figure 1 illustrates one embodiment of a control schematlc utilized for changing the motor terminal connec-tions for shifting from one torque mode to another.
Electrical power is connected to the line terminals Ll, L2 and L3 and passes through a conventional motor circuit breaker MCP or other circuit protection and disconnect devices. From the main circuit breaker MCP power passes through the contactor MC -to terminals Tl, T2 and T3. Con-nected to the load side of the contactor MC is a high mode contactor ~ which connects electrical power through three overloads to motor terminals T7, T8 and T9. Also connect-ed to the load side of the high mode contactor H is the medium mode contactor M which connects power to terminals T4, T5 and T6. Finally, a wye connection is connected to the load side of the high mode contactor H through an overload and parallel to the low mode contactor M. Con-trol power is supplied in a conventional manner by con-necting a step-down transformer to the line terminals Ll and L2. Control of the motor is initiated by first de-pressing the start pushbutton and completing the circuitXl, stop pushbutton, start pushbutton, the motor starter coil MC, the three overloads, H-OL, and X2. When the motor starter MC is energized, the contact MC-l closes and latches the start pushbutton in the start position and MC-2 closes and energizes the timer TDl by completing the circuit Xl, MC-2, TDl, and X2. At the same time MC-2 energizes the H contactor ~or the high torque mode b~
connecti.ng Xl, TDl-l, TDlA-l, M-l, L 1, H, and X2. At this 3~
4 48,969 point powex is connected to the motor from Ll, L2, L3, the circuit breaker MCP, contactor MC, to terminals Tl, T2 and T30 Th~ high mode contactor H in its energized position connects terminal T7 to termlnal T2, terminal T8 to termi-nal T3, and terminal T9 to terminal Tl through three over-l.oads sized to protect the motor in the high mode state~
As can be seen in Figure 2 the high torque mode contactor connects the windings into a full delta configuration.
Monitoring means shown here as an incandescent light may b2 paralleled with the H contactor to show that the motor is now running in the high torque mode. Also an elapsed time meter designated ETM may be parallel with the H
contactor to measure the total amount of time that the motor runs in the high torque configuration.
After the motor has run in the high mode for a predetermined time set on the time delay relay TDl, TDl energizes rrDlA by completing the circuit Xl, TDl 2, TDlA, X2. TDlA deenergizes the high mode circuit XL, TDl-TDlA-l, M-l, L-l, H, X2 and energizes low mode circuit Xl, M-OL, TDlA~2, L-OL, H-3, M-3, SS4, L, X2. It will be noted that an interlock L-l is in series with the high mode contactor h to prevent operation in the high mode when the low mode circuit is energized. The low mode has similar monitoring and elapsed time meters parallel with the low mode contac-tor L as previously described. As can be seen in Figure l, when the low mode contactor L is energized, terminals T7, T8 and T9 are shorted toget.her through the low over~
load to form a wye connection which connects -the motor windings in a wye configuration shown in Figure 4 for the low torque mode connection. A timer TD4 is energized by the low mode contactor L by completing the circuit Xl, M-OL, I.-3, RS-2, TD4, X2. This time delay relay allows the operato.r to set a predetermined time for running the motor in the low torque mode. After the time set on the timer TD4 has elapsed, the timer energizes an alarm monitor shown here as an incandescent lamp by compl~ting the circuit Xl, reset pushbutton, TD4, incandescent lamp, X20 A reset relay RS is also energized and contact RS-2 bypasses .
~7~3~
As can be seen in Figure 2 the high torque mode contactor connects the windings into a full delta configuration.
Monitoring means shown here as an incandescent light may b2 paralleled with the H contactor to show that the motor is now running in the high torque mode. Also an elapsed time meter designated ETM may be parallel with the H
contactor to measure the total amount of time that the motor runs in the high torque configuration.
After the motor has run in the high mode for a predetermined time set on the time delay relay TDl, TDl energizes rrDlA by completing the circuit Xl, TDl 2, TDlA, X2. TDlA deenergizes the high mode circuit XL, TDl-TDlA-l, M-l, L-l, H, X2 and energizes low mode circuit Xl, M-OL, TDlA~2, L-OL, H-3, M-3, SS4, L, X2. It will be noted that an interlock L-l is in series with the high mode contactor h to prevent operation in the high mode when the low mode circuit is energized. The low mode has similar monitoring and elapsed time meters parallel with the low mode contac-tor L as previously described. As can be seen in Figure l, when the low mode contactor L is energized, terminals T7, T8 and T9 are shorted toget.her through the low over~
load to form a wye connection which connects -the motor windings in a wye configuration shown in Figure 4 for the low torque mode connection. A timer TD4 is energized by the low mode contactor L by completing the circuit Xl, M-OL, I.-3, RS-2, TD4, X2. This time delay relay allows the operato.r to set a predetermined time for running the motor in the low torque mode. After the time set on the timer TD4 has elapsed, the timer energizes an alarm monitor shown here as an incandescent lamp by compl~ting the circuit Xl, reset pushbutton, TD4, incandescent lamp, X20 A reset relay RS is also energized and contact RS-2 bypasses .
~7~3~
5 48,g69 the delay con~act TD4 and latches the light in the ON
posi-tion~ The normally cl.osed contact RS-l deenergizPs the timer TD4 and resets it. The reset pushbutton is provided 50 ~hat the operator can acknowledge the alarm condition and turn off the light by disconnecting the alarm circuit.
If while operating in the low torque mode, loading on the motor should be increased, t~e low torque mode overload L-OL senses an increase in current and disconnects the low mode contactor by Gpening the circuit Xl, M-OL, TDlA-2, L-OL, H-3, M-3, SS-4, L, X2, and energi~es the medlum torque mode contactor M by completing the circuit Xl, M-OL, TDlA-2, L-OL, H-2, L-2, SS2, M, X2. The medium mode contactor M connects term.inal T7 to terminal T6, terminal T8 to terminal T4 and terminal T9 to terminal T5 to form a partial delta partial wye configuration as shown in Figure 3. Time delay relay TD3 is parallel with the medium mode contactor M and time delay contact TD3 bypasses the low ove:rload by completing the clrcuit Xl, M-2, TD3, H-2, L-2, SS-2, M, X2 and allows the motor to run in the medium torque mode for a predetermined time limitO When the time set on the time delay relay TD3 expires, the time delay relay contact TD3 opens and shif~s the motor from the medium torque mode by opening the medium mode contactor M circuit and with the low overload con-tacts now closed, the motor again runs in the low mode by energizing the low mode contactor with -the circuit Xl, M-OL, TDlA-2, L-OL, H-3, M-3, SS4, L, X2. If heavy loading s-till persists in the low torque mode, the low torque mode overloads L-OL will again shift the contactor back to the 3Q medium mode by energizing the medium torque mode contactor M and the time delay relay TD3 starts timing again. If before the time set on the time delay relay TD3 lapses and loading on the motor continues to increase while the motor is in the medium torque mode, the medium -torque mode overloads M-OL opens and disconnects the medium torque mode contactor M and shifts the motor into the high torque mode by comple~ing the circuit Xl, M-OL, delay contact TDlA-3, M-l/ L-l, H, and X2. Time delay relay TD2 is also
posi-tion~ The normally cl.osed contact RS-l deenergizPs the timer TD4 and resets it. The reset pushbutton is provided 50 ~hat the operator can acknowledge the alarm condition and turn off the light by disconnecting the alarm circuit.
If while operating in the low torque mode, loading on the motor should be increased, t~e low torque mode overload L-OL senses an increase in current and disconnects the low mode contactor by Gpening the circuit Xl, M-OL, TDlA-2, L-OL, H-3, M-3, SS-4, L, X2, and energi~es the medlum torque mode contactor M by completing the circuit Xl, M-OL, TDlA-2, L-OL, H-2, L-2, SS2, M, X2. The medium mode contactor M connects term.inal T7 to terminal T6, terminal T8 to terminal T4 and terminal T9 to terminal T5 to form a partial delta partial wye configuration as shown in Figure 3. Time delay relay TD3 is parallel with the medium mode contactor M and time delay contact TD3 bypasses the low ove:rload by completing the clrcuit Xl, M-2, TD3, H-2, L-2, SS-2, M, X2 and allows the motor to run in the medium torque mode for a predetermined time limitO When the time set on the time delay relay TD3 expires, the time delay relay contact TD3 opens and shif~s the motor from the medium torque mode by opening the medium mode contactor M circuit and with the low overload con-tacts now closed, the motor again runs in the low mode by energizing the low mode contactor with -the circuit Xl, M-OL, TDlA-2, L-OL, H-3, M-3, SS4, L, X2. If heavy loading s-till persists in the low torque mode, the low torque mode overloads L-OL will again shift the contactor back to the 3Q medium mode by energizing the medium torque mode contactor M and the time delay relay TD3 starts timing again. If before the time set on the time delay relay TD3 lapses and loading on the motor continues to increase while the motor is in the medium torque mode, the medium -torque mode overloads M-OL opens and disconnects the medium torque mode contactor M and shifts the motor into the high torque mode by comple~ing the circuit Xl, M-OL, delay contact TDlA-3, M-l/ L-l, H, and X2. Time delay relay TD2 is also
6 4~,96g energized and the medium torque mode overload M OL is bypassed for a preset time by completing the circuit Xl, H-l, TD2, TDlA~--3, M~l, L-l, H, and X2. After the motor runs in the high torque mode for the predetermined tlme set on time delay relay TD2, and the TD2 contact opens, thus discon-necting the high mode contactor H and the low mode contactor L will again be energized by the circuit Xl, M-OL, TDlA-2, ~--OL, H-3, M~3, SS4, L, and X2.
However, if before the time set on the timer TD2 lapses and loading on the motor continues to increase while the motor is in the high torque mode, the high torque mode overloads H-OL opens deenergizing the motor starter MC and shuts down the motor. The overloads H-OL also energize an overload alarm circuit by completing the circuit Xl, reset pushbutton, OLR, H-OL, and X2. Contact OLR 1 bypasses the high overloads to latch the overload relay in the on position and contact over OLR-2 energizes an incandescent lamp or other monitoring means to alarm the operator. The reset push-bu~ton allows the operator to acknowledge the alarm condition.
I~ can be readily seen that there is provided in this application a novel and unique method of controlling a multiple horsepower/torque motor by sensing the loading and torque demands of the motor and changing the connec-tion of electrical power to the windings of the motor while the meter is continuously under load so that the motor windings are connected in either a full delta con-nection, a partial delta partial Y connec-tion, or a full Y
connection, in response to the motor loading conditions.
However, if before the time set on the timer TD2 lapses and loading on the motor continues to increase while the motor is in the high torque mode, the high torque mode overloads H-OL opens deenergizing the motor starter MC and shuts down the motor. The overloads H-OL also energize an overload alarm circuit by completing the circuit Xl, reset pushbutton, OLR, H-OL, and X2. Contact OLR 1 bypasses the high overloads to latch the overload relay in the on position and contact over OLR-2 energizes an incandescent lamp or other monitoring means to alarm the operator. The reset push-bu~ton allows the operator to acknowledge the alarm condition.
I~ can be readily seen that there is provided in this application a novel and unique method of controlling a multiple horsepower/torque motor by sensing the loading and torque demands of the motor and changing the connec-tion of electrical power to the windings of the motor while the meter is continuously under load so that the motor windings are connected in either a full delta con-nection, a partial delta partial Y connec-tion, or a full Y
connection, in response to the motor loading conditions.
Claims (3)
1. A circuit for controlling a multirated motor, comprising:
a) a high torque contactor for connecting electrical power to the windings of a multi-rated motor such that the windings are first connected in a .DELTA.-delta configuration;
b) a first timer means electrically connected to the high torque contactor and a low torque contactor for de-energizing the high torque contactor and energizing the low torque contactor to change the connection of electrical power to the windings such that the windings are connected in a ?-wye configuration after a. predetermined time interval;
c) a low torque overload means connected to the low torque contactor and the ?-wye connected windings for causing the low torque contactor to de-energize and energize a medium torque contactor to change the connection of electrical power to the windings such that the windings are connected in a ?-.DELTA.-partial wye, partial delta configuration if the current in the windings exceed a predetermined current level;
d) a medium torque monitoring means for causing the windings to be switched back to a wye configuration after operating a predetermined time in the partial wye, partial delta configuration;
e) a medium torque overload means connected to the medium torque contactor and the ?-.DELTA. partial wye, partial delta, windings for de-energizing the medium torque contactor and energizing the high torque contactor to change the connection of electrical power to the windings such that the windings are connected in a .DELTA.-delta configuration if the current in the windings exceed a predetermined current level;
f) a high torque monitoring means for causing the windings to be switched back to wye, configuration after operating a predetermined time in the delta configuration;
and g) high torque overload means connected to the high torque contactor and the .DELTA.-delta connected windings for causing the disconnection of electrical power to the windings if the current in the windings exceed a predetermined current level.
a) a high torque contactor for connecting electrical power to the windings of a multi-rated motor such that the windings are first connected in a .DELTA.-delta configuration;
b) a first timer means electrically connected to the high torque contactor and a low torque contactor for de-energizing the high torque contactor and energizing the low torque contactor to change the connection of electrical power to the windings such that the windings are connected in a ?-wye configuration after a. predetermined time interval;
c) a low torque overload means connected to the low torque contactor and the ?-wye connected windings for causing the low torque contactor to de-energize and energize a medium torque contactor to change the connection of electrical power to the windings such that the windings are connected in a ?-.DELTA.-partial wye, partial delta configuration if the current in the windings exceed a predetermined current level;
d) a medium torque monitoring means for causing the windings to be switched back to a wye configuration after operating a predetermined time in the partial wye, partial delta configuration;
e) a medium torque overload means connected to the medium torque contactor and the ?-.DELTA. partial wye, partial delta, windings for de-energizing the medium torque contactor and energizing the high torque contactor to change the connection of electrical power to the windings such that the windings are connected in a .DELTA.-delta configuration if the current in the windings exceed a predetermined current level;
f) a high torque monitoring means for causing the windings to be switched back to wye, configuration after operating a predetermined time in the delta configuration;
and g) high torque overload means connected to the high torque contactor and the .DELTA.-delta connected windings for causing the disconnection of electrical power to the windings if the current in the windings exceed a predetermined current level.
2. A circuit for controlling a multirated motor as recited in claim 1 wherein the medium torque monitoring means comprises a second timer means connected to the medium torque contactor and the partial wye, partial delta connected windings for causing the medium torque contactor to de-energize and the low torque contactor to energize to change the connection of electrical power to the windings such that the windings are connected in a ?-wye configuration after a pre-determined time interval.
3. A circuit for controlling a multirated motor as recited in claim 2 wherein the high torque monitoring means comprises a third timing means connected to the high torque contactor and the .DELTA.-delta connected windings for causing the high torque contactor to de-energize and the low torque contactor to energize to change the connection of electrical power to the windings such that the windings are connected in a ?-wye configuration after a predetermined time interval.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US17804780A | 1980-08-14 | 1980-08-14 | |
| US178,047 | 1980-08-14 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1187930A true CA1187930A (en) | 1985-05-28 |
Family
ID=22650966
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000382419A Expired CA1187930A (en) | 1980-08-14 | 1981-07-23 | Circuit for controlling multiple rated motors |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1187930A (en) |
-
1981
- 1981-07-23 CA CA000382419A patent/CA1187930A/en not_active Expired
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US4434394A (en) | Circuit for controlling multiple rated motors | |
| US4119861A (en) | Starting apparatus for gas turbine-generator mounted on electric motor driven motorcar | |
| US4563624A (en) | Variable speed refrigeration compressor | |
| US6158553A (en) | Curtailed operation of multiple-wound induction motor following inverter failure | |
| EP0093615B1 (en) | Variable speed rotary electrical machines | |
| US4815567A (en) | Apparatus for controlling an A.C. powered elevator | |
| CA1187930A (en) | Circuit for controlling multiple rated motors | |
| JPS6321429B2 (en) | ||
| US4967132A (en) | VSCF start system current estimator | |
| US2376299A (en) | Reversible hoist motor | |
| US2279228A (en) | Control system | |
| US4500825A (en) | Self-starting single-phase synchronous motor | |
| JPH0736402Y2 (en) | Induction motor pole number switching device | |
| GB2289347A (en) | Controlling compressor start-up | |
| US1797009A (en) | Control system | |
| Mungenast | Design and application of a solid-state AC motor starter | |
| JPH07203695A (en) | Star-delta starter for main motor | |
| SU917302A1 (en) | Excitation current regulation system for slip clutch | |
| EP0442848B1 (en) | Variable-speed AC drive utilizing a short-circuit-rotor polyphase induction motor | |
| US3818316A (en) | Generator, synchronous motor and phase converter | |
| JPS6039396A (en) | Drive device of induction motor | |
| JPS5915267Y2 (en) | Slip frequency control device for induction motor using current source inverter | |
| EP0128671A2 (en) | Improvements in or relating to electric motors | |
| JPS60109799A (en) | Self-excited induction generator | |
| JPH0729703Y2 (en) | Induction motor stop control device |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |