Method and system device for multiple load-bearing of linear motor for magnetic levitation transportation
A method and system device for performing multi-carrying of a linear motor for magnetic levitation transportation is provided. With the method for performing multi-carrying of a linear motor for magnetic levitation transportation, linear motor traction power information and other linear motor carried information are generated, and the other linear motor carried information is transmitted through a channel for carrying the linear motor traction power information that is constructed based on a linear motor structure.
1 . A method for performing multi-carrying of a linear motor for magnetic levitation transportation, comprising:
generating linear motor traction power information and other linear motor carried information; and
transmitting the other linear motor carried information through a channel for carrying the linear motor traction power information that is constructed based on a linear motor structure;
wherein the other linear motor carried information comprises at least one of vehicle inductive power generation power information and a train communication signal, and wherein the vehicle inductive power generation power information is generated by a power generation output converter component in a converter module matching the linear motor structure.
2 . The method according to claim 1 , wherein the generating linear motor traction power information and other linear motor carried information comprises:
generating the linear motor traction power information based on a traction demand of a magnetic levitation train;
generating the vehicle inductive power generation power information according to a power generation control function; and/or
generating the train communication signal according to a communication control function, wherein
the vehicle inductive power generation power information, the train communication signal and the linear motor traction power information are in frequency bands different from each other.
3 . The method according to claim 2 , wherein the generating the vehicle inductive power generation power information according to a power generation control function comprises:
calculating an output terminal voltage U according to an output terminal voltage formula of the power generation control function,
U
=
∑
n
=
1
m
L
n
*
di
dt
+
i
*
∑
n
=
1
m
R
n
+
U
^
,
L
=
∑
n
=
1
m
L
n
wherein m represents a number of stator sections of a linear motor, L represents a total inductance of the stator sections of the linear motor, L n represents an inductance of a nth stator section, 1≤n≤m, R n represents a resistance of a stator winding of the nth stator section corresponding to L n , i represents a stator current, and Û represents a back electromotive force generated by the magnetic levitation train on a stator winding;
calculating an output traction force F transaction (t) according to an output traction force formula constructed based on the traction demand of the magnetic levitation train and the power generation control function,
F
traction
(
t
)
=
A
*
K
V
+
B
*
(
1
-
K
V
)
wherein A and B each represents a parameter related to the stator current i and a vehicle structure of the magnetic levitation train, and K v represents a speed factor;
calculating an output voltage U generation according to an output voltage formula constructed based on the power generation control function,
U
generation
=
C
*
(
1
-
K
V
)
+
D
*
V
*
K
V
wherein C represents a parameter related to the stator current i and the structure of the magnetic levitation train, D represents a parameter related to the structure of the magnetic levitation train, and V represents a speed of the magnetic levitation train;
calculating a traction power f(t) traction based on a product of the output traction force F traction (t) and V;
calculating the vehicle inductive power generation power f(t) generation by multiplying the output voltage U generation by a current of a vehicle inductive power generation coil; or
calculating the vehicle inductive power generation power f(t) generation by dividing a square of the output voltage U generation by an equivalent resistance of a receiving loop of the vehicle inductive power generation coil.
4 . The method according to claim 3 , further comprising:
setting a speed threshold of the magnetic levitation train and a weighting coefficient of the speed factor K v according to a preset control strategy, wherein the speed threshold is not less than zero and not greater than a maximum speed;
determining the speed factor K v of a current speed of the magnetic levitation train based on the speed threshold;
determining whether a requirement for cogging power generation is met by comparing the current speed with the speed threshold;
generating power based on the vehicle inductive power generation power information, if the requirement for cogging power generation is not met; and
cutting off the power generated based on the vehicle inductive power generation power information and performing cogging power generation, if the requirement for cogging power generation is met.
5 . The method according to claim 2 , wherein the generating the train communication signal according to a communication control function comprises:
acquiring digital communication information;
obtaining an analog train communication signal by performing a digital-to-analog conversion on the digital communication information according to the communication control function.
6 . The method according to claim 2 , further comprising one of the following:
performing first band-pass filtering on the linear motor traction power information and the other linear motor carried information, to pass the linear motor traction power information and signals related to braking and traction control;
performing second band-pass filtering on the linear motor traction power information and the other linear motor carried information, to pass the vehicle inductive power generation power information and signals related to power generation control; and
performing third band-pass filtering on the linear motor traction power information and the other linear motor carried information, to pass the train communication signal and signals related to train control.
7 . The method according to claim 1 , wherein the transmitting the other linear motor carried information through a channel for carrying the linear motor traction power information that is constructed based on a linear motor structure comprises one of the following:
inputting at least one of the vehicle inductive power generation power information and the train communication signal to stator sections of the linear motor structure in a three-phase manner, and receiving at least one of the vehicle inductive power generation power information and the train communication signal through a rotor of the linear motor structure or a communication transceiver coil;
inputting at least one of the vehicle inductive power generation power information and the train communication signal to stator sections of the linear motor structure in a single-phase manner, and receiving at least one of the vehicle inductive power generation power information and the train communication signal through a rotor of the linear motor structure or a communication transceiver coil; and
inputting at least one of the vehicle inductive power generation power information and the train communication signal to stator sections of the linear motor structure in a two-single phase manner, and receiving at least one of the vehicle inductive power generation power information and the train communication signal through a rotor of the linear motor structure or a communication transceiver coil.
8 . The method according to claim 7 , wherein the inputting at least one of the vehicle inductive power generation power information and the train communication signal to stator sections of the linear motor structure in a three-phase manner comprises one of the following:
inputting at least one of the vehicle inductive power generation power information and the train communication signal directly to the stator sections of the linear motor structure in a three-phase manner;
performing independent transformation on at least one of the vehicle inductive power generation power information and the train communication signal, and inputting the transformed at least one of the vehicle inductive power generation power information and the train communication signal to the stator sections of the linear motor structure in a three-phase manner; and
performing independent primary winding transformation on at least one of the vehicle inductive power generation power information and the train communication signal, and inputting the transformed at least one of the vehicle inductive power generation power information and the train communication signal to the stator sections of the linear motor structure in a three-phase manner.
9 . The method according to claim 7 , wherein the inputting at least one of the vehicle inductive power generation power information and the train communication signal to stator sections of the linear motor structure in a single-phase manner comprises one of the following:
inputting at least one of the vehicle inductive power generation power information and the train communication signal directly to two of three-phase terminals of the stator sections of the linear motor structure in a single-phase manner;
performing independent transformation on at least one of the vehicle inductive power generation power information and the train communication signal, and inputting the transformed at least one of the vehicle inductive power generation power information and the train communication signal to two of three-phase terminals of the stator sections of the linear motor in a single-phase manner; and
performing independent primary winding transformation on at least one of the vehicle inductive power generation power information and the train communication signal both of which are in the single-phase manner; and adding at least one of the vehicle inductive power generation power information and the train communication signal to two of three phases corresponding to the linear motor traction power information, and inputting the transformed at least one of the vehicle inductive power generation power information and the train communication signal to the stator sections of the linear motor structure.
10 . The method according to claim 7 , wherein the inputting at least one of the vehicle inductive power generation power information and the train communication signal to stator sections of the linear motor structure in a two-single phase manner comprises one of the following:
inputting at least one of the vehicle inductive power generation power information and the train communication signal directly to the stator sections of the linear motor structure in a two-single phase manner, wherein two of three-phase terminals of the stator sections of the linear motor structure serve as a common input terminal, and another terminal serves as a common ground terminal;
performing independent transformation on at least one of the vehicle inductive power generation power information and the train communication signal both of which are in the two-single manner, and inputting the transformed at least one of the vehicle inductive power generation power information and the train communication signal to the stator sections of the linear motor structure, wherein two of three-phase terminals of the stator sections of the linear motor structure serve as a common input terminal, and another terminal serves as a common ground terminal;
performing independent primary winding transformation on at least one of the vehicle inductive power generation power information and the train communication signal both of which are in the two-single manner, and inputting the transformed at least one of vehicle inductive power generation power information and the train communication signal to the stator sections of the linear motor structure, wherein two of three-phase terminals of the stator sections of the linear motor structure serve as a common input terminal, and another terminal serves as a common ground terminal; and
inputting in series at least one of the vehicle inductive power generation power information and the train communication signal both of which are in the two-single manner, and inputting at least one of the vehicle inductive power generation power information and the train communication signal connected in series directly to two of three-phase terminals of the stator sections of the linear motor structure, or performing independent transformation on at least one of the vehicle inductive power generation power information and the train communication signal connected in series, and inputting the transformed at least one of the vehicle inductive power generation power information and the train communication signal to two of three-phase terminals of the stator sections of the linear motor structure.
11 . The method according to claim 1 , wherein the transmitting the other linear motor carried information through a channel for carrying the linear motor traction power information that is constructed based on a linear motor structure comprises:
combining the linear motor traction power information with the vehicle inductive power generation power information to obtain a first combined information, transmitting the first combined information through stator sections of the linear motor structure, and receiving the first combined information through a rotor of the linear motor structure; or
combining the linear motor traction power information with the train communication signal to obtain a second combined information, transmitting the second combined information through the stator sections of the linear motor structure, and receiving the second combined information through the rotor of the linear motor structure; or,
combining the linear motor traction power information, the vehicle inductive power generation power information, and the train communication signal to obtain a third combined information, transmitting the third combined information through the stator sections of the linear motor structure, and receiving the third combined information through the rotor of the linear motor structure.
12 . The method according to claim 11 , further comprising:
performing transformation on the first combined information, and transmitting the transformed first combined information through the stator sections of the linear motor structure; or
performing transformation on the second combined information, and transmitting the transformed second combined information through the stator sections of the linear motor; or
performing transformation on the third combined information, and transmitting the transformed third combined information through the stator sections of the linear motor.
13 . The method according to claim 1 , wherein the other linear motor carried information comprises a train communication signal, and the transmitting the other linear motor carried information through a channel for carrying the linear motor traction power information that is constructed based on a linear motor structure comprises:
inputting the train communication signal to stator sections of the linear motor structure in a three-phase manner, a single-phase manner or a two-single phase manner, and receiving the train communication signal in a two-channel manner or a single-channel manner through a rotor of the linear motor structure; and
inputting the train communication signal to the rotor of the linear motor structure in the two-channel manner or the single-channel manner, and receiving the train communication signal through the stator sections of the linear motor structure.
14 . The method according to claim 1 , further comprising:
charging the magnetic levitation train by using a charging pile in a case that the magnetic levitation train is stopped at a station or is maintained.
15 . The method according to claim 1 , wherein
the linear motor structure comprises a unilateral linear motor, a bilateral linear motor and a multilateral linear motor in type; and
a rotor of the linear motor comprises a permanent magnet rotor, an electric excitation rotor and a permanent magnet-electric excitation hybrid rotor in magnetic type.
16 . A system device for performing multi-carrying of a linear motor for magnetic levitation transportation, comprising:
a linear motor structure and a converter module matching the linear motor structure, wherein
the linear motor structure comprises stator sections arranged on a ground track and a rotor arranged on a magnetic levitation train, and
the converter module is configured to generate linear motor traction power information and other linear motor carried information, and transmit the other linear motor carried information through a channel for carrying the linear motor traction power information that is constructed based on the linear motor structure;
wherein the other linear motor carried information comprises at least one of vehicle inductive power generation power information and a train communication signal, and wherein the vehicle inductive power generation power information is generated by a power generation output converter component in a converter module matching the linear motor structure.
17 . The system device according to claim 16 , wherein the converter module comprises:
a traction converter component, configured to generate the linear motor traction power information based on a traction demand of the magnetic levitation train;
a power generation output converter component, configured to generate the vehicle inductive power generation power information according to a power generation control function; and/or
a communication converter component, configured to generate the train communication signal according to a communication control function, wherein
the vehicle inductive power generation power information, the train communication signal and the linear motor traction power information are in frequency bands different from each other.
18 . The system device according to claim 17 , wherein
the power generation output converter component is further configured to calculate an output terminal voltage U according to an output terminal voltage formula of the power generation control function,
U
=
∑
n
=
1
m
L
n
*
di
dt
+
i
*
∑
n
=
1
m
R
n
+
U
^
,
L
=
∑
n
=
1
m
L
n
wherein m represents a number of stator sections of a linear motor, L represents a total inductance of the stator sections of the linear motor, L n represents an inductance of a nth stator section, 1≤n≤m, R n represents a resistance of a stator winding of the nth stator section corresponding to L n , i represents a stator current, and Û represents a back electromotive force generated by the magnetic levitation train on a stator winding;
the power generation output converter component is further configured to calculate an output traction force F traction (t) according to an output traction force formula constructed based on the traction demand of the magnetic levitation train and the power generation control function,
F
traction
(
t
)
=
A
*
K
V
+
B
*
(
1
-
K
V
)
wherein A and B each represents a parameter related to the stator current i and a vehicle structure of the magnetic levitation train, and K v represents a speed factor; and
the power generation output converter component is further configured to:
calculate an output voltage U generation according to an output voltage formula constructed based on the power generation control function,
U
generation
=
C
*
(
1
-
K
V
)
+
D
*
V
*
K
V
wherein C represents a parameter related to the stator current i and the vehicle structure of the magnetic levitation train, D represents a parameter related to the vehicle structure of the magnetic levitation train, and V represents a speed of the magnetic levitation train;
calculate a traction power f(t) traction based on a product of the output traction force F traction (t) and V;
calculate the vehicle inductive power generation power f(t) generation by multiplying the output voltage U generation by a current of a vehicle inductive power generation coil; or
calculate the vehicle inductive power generation power f(t) generation by dividing a square of the output voltage U generation by an equivalent resistance of a receiving loop of the vehicle inductive power generation coil.
19 . The system device according to claim 18 , further comprising:
a power generation switching handover control module, configured to set a speed threshold of the magnetic levitation train and a weighting coefficient of the speed factor K v according to a preset control strategy, wherein the speed threshold is not less than zero and not greater than a maximum speed,
the power generation switching handover control module is further configured to determine the speed factor K v of a current speed of the magnetic levitation train based on the speed threshold;
the power generation switching handover control module is further configured to determine whether a requirement for cogging power generation is met by comparing the current speed with the speed threshold;
the power generation switching handover control module is further configured to generate power based on the vehicle inductive power generation power information if the requirement for cogging power generation being not met; and
the power generation switching handover control module is further configured to cut off the power generated based on the vehicle inductive power generation power information and perform cogging power generation if the requirement for cogging power generation being met.
20 . The system device according to claim 17 , wherein
the communication converter component is configured to acquire digital communication information, and
the communication converter component is further configured to obtain an analog train communication signal by performing a digital-to-analog conversion on the digital communication information according to the communication control function.
21 . The system device according to claim 17 , wherein
the power generation output converter component and/or the communication converter component comprises a three-phase converter, a single-phase converter, or a two-single phase converter.
22 . The system device according to claim 17 , wherein
the power generation output converter component and/or the communication converter component is further configured to input at least one of the vehicle inductive power generation power information and the train communication signal to the stator sections of the linear motor structure in a three-phase manner; and
the rotor of the linear motor structure is configured to receive at least one of the vehicle inductive power generation power information and the train communication signal.
23 . The system device according to claim 17 , further comprising: an independent transformer component for power generation and/or communication, wherein
the independent transformer component for power generation and/or communication is configured to perform independent transformation on at least one of the vehicle inductive power generation power information and the train communication signal and input the transformed at least one of the vehicle inductive power generation power information and the transformed train communication signal to the stator sections of the linear motor structure in a three-phase manner; and
the rotor of the linear motor structure is configured to receive at least one of the vehicle inductive power generation power information and the train communication signal.
24 . The system device according to claim 17 , further comprising: an independent primary winding transformer component, wherein
the independent primary winding transformer component is configured to perform independent primary winding transformation on at least one of the vehicle inductive power generation power information and the train communication signal;
the independent primary winding transformation component is further configured to input the transformed at least one of the vehicle inductive power generation power information and the train communication signal to the stator sections of the linear motor structure in a three-phase manner; and
the rotor of the linear motor structure is configured to receive at least one of the vehicle inductive power generation power information and the train communication signal.
25 . The system device according to claim 17 , wherein
the power generation output converter component and/or the communication converter component is further configured to input at least one of the vehicle inductive power generation power information and the train communication signal directly to two of three-phase terminals of the stator sections of the linear motor structure in a single-phase manner; and
the rotor of the linear motor structure is configured to receive at least one of the vehicle inductive power generation power information and the train communication signal.
26 . The system device according to claim 17 , further comprising: an independent transformer component for power generation and/or communication, wherein
the independent transformer component for power generation and/or communication is configured to perform independent transformation on at least one of the vehicle inductive power generation power information and the train communication signal and input the transformed at least one of the vehicle inductive power generation power information and the train communication signal to two of three-phase terminals of the stator sections of the linear motor structure in a single-phase manner; and
the rotor of the linear motor structure is configured to receive at least one of the vehicle inductive power generation power information and the train communication signal.
27 . The system device according to claim 17 , further comprising: an independent primary winding transformer component, wherein
the independent primary winding transformer component is configured to: perform independent primary winding transformation on at least one of the vehicle inductive power generation power information and the train communication signal both of which are in the single-phase manner; and add at least one of the vehicle inductive power generation power information and the train communication signal to two of three phases corresponding to the linear motor traction power information;
the independent primary winding transformer component is further configured to input the transformed linear motor traction power information and the transformed at least one of vehicle inductive power generation power information and the train communication signal to the stator sections of the linear motor structure, and
the rotor of the linear motor structure is configured to receive at least one of the vehicle inductive power generation power information and the train communication signal.
28 . The system device according to claim 17 , further comprising:
the power generation output converter component and/or the communication converter component is configured to input at least one of the vehicle inductive power generation power information and the train communication signal directly to the stator sections of the linear motor structure in a two-single phase manner, wherein two of three-phase terminals of the stator sections of the linear motor structure serve as a common input terminal, and another terminal serves as a common ground terminal; and
the rotor of the linear motor structure is configured to receive at least one of the vehicle inductive power generation power information and the train communication signal.
29 . The system device according to claim 17 , further comprising: an independent transformer component for power generation and/or communication, wherein the independent transformer component for power generation and/or communication is configured to perform independent transformation on at least one of the vehicle inductive power generation power information and the train communication signal both of which are in the two-single manner; and input the transformed at least one of vehicle inductive power generation power information and the train communication signal to the stator sections of the linear motor structure, wherein two of three-phase terminals of the stator sections of the linear motor structure serve as a common input terminal, and another terminal serves as a common ground terminal; and
the rotor of the linear motor structure is configured to receive at least one of the vehicle inductive power generation power information and the train communication signal.
30 . The system device according to claim 17 , further comprising: an independent primary winding transformer component, wherein
the independent primary winding transformer component is configured to perform independent primary winding transformation on at least one of the vehicle inductive power generation power information and the train communication signal both of which are in the two-single manner;
the independent primary winding transformer component is further configured to input the transformed at least one of the vehicle inductive power generation power information and the train communication signal to the stator sections of the linear motor structure, wherein two of three-phase terminals of the stator sections of the linear motor structure serve as a common input terminal, and another terminal serves as a common ground terminal; and
the rotor of the linear motor structure is configured to receive at least one of the vehicle inductive power generation power information and the train communication signal.
31 . The system device according to claim 17 , further comprising: an independent transformer component for power generation and/or communication, wherein
power generation output converter components and/or communication converter components in the two-single phase are connected in series, to input in series at least one of the vehicle inductive power generation power information and the train communication signal in a two-single phase;
the power generation output converter components and/or the communication converter components are configured to input at least one of the vehicle inductive power generation power information and the train communication signal obtained by inputting in series directly to two of the three-phase terminals of the stator sections of the linear motor structure; or,
the independent transformer component for power generation and/or communication is configured to perform transformation on at least one of the vehicle inductive power generation power information and the train communication signal obtained by inputting in series;
the independent transformer component for power generation and/or communication is further configured to connect the transformed at least one of the vehicle inductive power generation power information and the train communication signal to two of three-phase terminals of the stator sections of the linear motor; and
the rotor of the linear motor structure is configured to receive at least one of the vehicle inductive power generation power information and the train communication signal.
32 . The system device according to claim 17 , further comprising: an integrated traction and power generation converter component, an integrated traction and communication converter component, and an integrated traction, power generation and communication converter component, wherein
the integrated traction and power generation converter component comprises functions of the traction converter component and the power generation output converter component;
the integrated traction and communication converter component comprises functions of the traction converter component and the communication converter component;
the integrated traction, power generation and communication converter component comprises functions of the traction converter component, the power generation output converter component and the communication converter component;
the integrated traction and power generation converter component is configured to combine the linear motor traction power information with the vehicle inductive power generation power information to obtain a first combined information, wherein the first combined information is transmitted through the stator sections of the linear motor structure, and is received through the rotor of the linear motor structure;
the integrated traction and communication converter component is configured to combine the linear motor traction power information with the train communication signal to obtain a second combined information, wherein the second combined information is transmitted through the stator sections of the linear motor structure, and is received through the rotor of the linear motor structure; or,
the integrated traction, power generation and communication converter component is configured to combine the linear motor traction power information, the vehicle inductive power generation power information, and the train communication signal to obtain a third combined information, wherein the third combined information is transmitted through the stator sections of the linear motor structure, and is received through the rotor of the linear motor structure.
33 . The system device according to claim 32 , further comprising: an independent transformer component, wherein
the independent transformer component is configured to perform independent transformation on the first combined information, wherein the transformed first combined information is transmitted through the stator sections of the linear motor structure;
the independent transformer component is configured to perform independent transformation on the second combined information, wherein the transformed second combined information is transmitted through the stator sections of the linear motor structure; or
the independent transformer component is configured to perform independent transformation on the third combined information, wherein the transformed third combined information is transmitted through the stator sections of the linear motor structure.
34 . The system device according to claim 17 , wherein the system device further comprises:
a first band-pass filter, configured to perform first band-pass filtering on the linear motor traction power information and the other linear motor carried information, to pass the linear motor traction power information and signals related to braking and traction control to be passed;
a second band-pass filter, configured to perform second band-pass filtering on the linear motor traction power information and the other linear motor carried information, to pass the train inductive power generation power information and signals related to power generation control to be passed; and
a third band-pass filter, configured to perform third band-pass filtering on the linear motor traction power information and the other linear motor carried information, to pass the train communication signal and signals related to train control.
35 . The system device according to claim 16 , wherein,
the rotor of the linear motor structure comprises a linear motor rotor and a vehicle inductive power generation coil;
the vehicle inductive power generation coil is configured to generate power generation power by coupling with the vehicle inductive power generation power information of the stator sections of the linear motor structure,
the vehicle inductive power generation coil is further configured to: couple with the train communication signal of the stator sections of the linear motor structure and transmit the coupled signal to a signal demodulator, to demodulate the coupled signal by the signal demodulator to obtain the train communication signal; and the vehicle inductive power generation coil is further configured to transmit an in-vehicle signal to the stator sections, and
the vehicle inductive power generation coil is further configured to transmit the in-vehicle signal to the stator sections of the linear motor structure.
36 . The system device according to claim 16 , further comprising: a communication transceiver coil, wherein
the rotor of the linear motor structure comprises a linear motor rotor and a vehicle inductive power generation coil;
the vehicle inductive power generation coil is configured to generate power generation power by coupling with the vehicle inductive power generation power information of the stator sections of the linear motor structure;
the communication transceiver coil is configured to: couple with the train communication signal of the stator sections of the linear motor structure and transmit the coupled signal to a signal demodulator, to demodulate the coupled signal by the signal demodulator to obtain the train communication signal;
the communication transceiver coil is further configured to transmit an in-vehicle signal to the stator sections of the linear motor structure, and wherein
in a case that the communication channel is a single channel, the communication transceiver coil is connected to two of three-phase terminals of the signal demodulator; and
in a case that the communication channel is a two-channel, two of the three-phase terminals of the signal demodulator each serves as a positive terminal of a single communication transceiver coil, and another terminal serves as a common ground terminal.
37 . The system device according to claim 36 , wherein
the communication transceiver coil is arranged on the magnetic levitation train, and is connected to a train control network.
38 . The system device according to claim 37 , wherein
the communication transceiver coil is arranged on a same vehicle as an in-vehicle operation control host and a train microwave communication antenna; or
the communication transceiver coil is arranged on the rotor of the linear motor, a magnetic levitation frame or a body of the magnetic levitation train.
39 . The system device according to claim 16 , further comprising a charging pile, wherein
the charging pile is connected with a body of the magnetic levitation train through a cable; and
the magnetic levitation train is charged by using the charging pile in a case that that magnetic levitation train is stopped at a station or is maintained.
40 . The system device according to claim 16 , wherein
the linear motor structure comprises a unilateral linear motor, a bilateral linear motor, and a multilateral linear motor in type; and
the rotor of the linear motor structure comprises a permanent magnet rotor, an electric excitation rotor and a permanent magnet-electric excitation hybrid rotor in magnetic type.