D.C. SERIES MOTOR FOR VEHICLES

Abstract: A D.C. motor for a vehicle driven by a pulsating current has an inductive shunt (9) connected in parallel with a main pole winding (7) of the motor (20). The inductive shunt has an inductance which is larger than 20% of an inductance of the main pole winding so that, a spark in the rectification operation is suppressed.

Description: D.C. MOTOR FOR A VEHICLE The present invention relates to a D.C. motor for rolling, and more particularly to a D.C. series motor for rolling stocks suitable for a pulsating current operation. A D.C. motor can be operated by either D.C. or pulsating current depending on a type and a quality of a power supply which feeds to the D.C. motor and a physical dimension of a filtering reactor mounted on rolling stocks. In a prior art D.C. motor for the vehicle, when it is operated by the pulsating current, a sparking voltage Es is generated due to a vector difference between a reactance voltage Er of the motor (a voltage between brushes of the D.C. motor) and a velocity e.m.f. Ef generated by interpole magnetic fluxes. Means for compensating resultant sparking voltage E (3V) of the arc voltage Es and a transformer e.m.f. Et of a main pole has not been proposed. As a result, a commutation performance of the pulsating current driven motor for the rolling stocks has been low due to the resultant sparking voltage Esp. It is an object of the present invention to provide a D.C. motor for a vehicle operated by a pulsating current having an inductive shunt connected in parallel to a main pole winding, which inductive shunt having an inductance larger than 20% of an inductance of the main pole winding, in order to improve a commutation performance in the pulsating current operation. Other objects, features and advantages of the present invention will be apparent from the following detailed description of the invention with reference to the accompanying drawings, in which: Fig. 1 shows a circuit configuration of a pulsating current motor to which the present invention is applicable; FIg. 2 shows a waveform illustrating a phase relationship between an armature current and an interpole magnetic flux of the pulsating current motor shown in Fig 1; Fig. 3 shows a vector diagram illustrating a relation among a reactance voltage, a velocity e.m.f. by the interpole magnetic flux and a sparking voltage of the pulsating current motor; Fig. 4 shows a vector diagram illustrating a relation among the reactance voltage, the velocity e.m.f. and the sparking voltage when a transformer e.m.f. is taken into consideration; Fig. 5 shows an equivalent circuit of a main pole under a field-weakening control; Fig. 6 shows a vector diagram illustrating a relation among the arc voltage, the transformer e.m.f. and a resultant sparking voltage when an inductance of an inductive shunt is varied; and Fig. 7 shows a relation between the inductance of the inductive shunt and the commutation spark numbers measured under the field-weakening control of the vehicle motor. One embodiment of the present invention is now explained with reference to the drawings. Fig. 1 shows an armature circuit of a pulsating current driven D.C. motor to which the present invention is applicable. A single phase A.C. power supply is supplied to a transformer 2 from a stringing through a pantagraph 1, and an output from the transformer 2 is supplied to a main motor 20 through a rectifier (e.g. a diode bridge rectifier) 3 and a filtering reactor 4. A main pole 7 has a pure resistor 8 connected in parallel thereto to minimize a pulsating current component flowing through the main pole 7 so that a field current is shunted by the pure resistor 8. An inductive shunt 9 and a field-weakening resistor 10 are selectively inserted by a switch 11 to effect a field-weakening control (high speed control). The inductive shunt 9 not only contributes to the fieldweakening control but also contributes to improve a rectification performance in the pulsating current driven D.C. motor. Fig. 2 shows current waveforms of currents flowing through an armature 5 and an interpole 6. A pulsating factor ii is generally expressed by EMI4.1 The pulsating factor is 50% - 25% at most in a present technology. When the pulsating current flows through the interpole circuit in the pulsating current operation, an eddy current flows through a magnetic circuit of the interpole because it includes a portion not completely laminated such as a magnetic frame so that an interpole magnetic flux f is retarded by ssi with respect to a current I and an amplitude thereof is reduced as shown in Fig. 2. Accordingly, the commutation performance is lowered than when the motor is D.C. driven. Fig. 3 illustrates a relation thereof. When the vehicle motor is D.C. driven, the commutation performance is high because a reactance voltage Er and a velocity e.m.f. E#DC generated by the interpole magnetic flux are equal. However, when the rolling stocks motor is pulsating current driven, the velocity e.m.f. E#C is changed to Ef by the eddy current and a phase thereof is shifted by ssi relative to the reactance voltage Er and an amplitude thereof is reduced. As a result, the reactance voltage Er and the velocity e.m.f. Ef generated by the interpole magnetic flux in the pulsating current operation do not cancell each other and a sparking voltage Es remains. This is one of the factors which lower the commutation performance in the pulsating current operation. Another factor to lower the rectification performance is the transformer e.m.f. of the main pole. This is described below. Fig. 4 shows a vector diagram illustrating a relation among the reactance voltage Er, the velocity e.m.f. E and the sparking voltage Es when the trans #DC former e.m.f. Et is taken into consideration. Since the main pole 7 has the field shunting resistor 8 to reduce the pulsating current component, the pulsating current component in the mainpole 7 is smaller than the pulsating current component in the interpole 6 and the armature 5 and a phase thereof is retarded by y. A phase of the transformer e.m.f. Et -is retarded by (r + ssf - 90 ) relative to the velocity e.m.f. E°DC where ssf is a phase difference between the mainpole magnetic flux and the main pole current. The commutation performance in the pulsating current operation is lowered because the resultant sparking voltage E of the transformer e.m.f. Et and the sparking voltage Es is not compensated. In Fig. 4, If denotes the pulsating current component of the main pole current and ff denotes the pulsating component of the main pole magnetic flux. The commutation performance in the pulsating current operation is not seriously lowered to compare with the D.C. operation in a full field operation (low speed operation) but it is lowered in the fieldweakening control (high speed operation). Therefore, only the field-weakening control is considered here. The reactance voltage Er, the velocity e.m.f. Ef by the interpole magnetic flux and the sparking voltage Es are constant for a given motor and cannot be changed. On the other hand, the magnitude and the phase of the transformer e.m.f. Et can be changed by appropriately selecting the inductance of the inductive shunt. Fig. 5 shows an equivalent circuit of the main pole under the field-weakening control. The current if in the main pole is given by EMI6.1 where i is a current in the interpole and the armature, Xi is the inductance of the inductive shunt, ri is the field-weakening resistance, Xf and rf are an inductive component and a resistive component of the mainpole winding and R5 is a field shunt resistance. Fig. 6 shows a vector diagram of the sparking voltage Es, the transformer e.m.f. Et and the resultant sparking voltage Esp when Xi is increased in the formula (2). As seen from Fig. 6, as the magnitude and the phase of the transformer e.m.f. Et are increased, the magnitude of the resultant sparking voltage E is reduced so that the commutation performance is improved. Fig. 7 shows a relation between the inductance of the inductive shunt and the rectification spark numbers (resultant sparking voltage Esp) measured under sp the field-weakening control of the vehicle motor. The spark numbers include 1 to 8, in which 1 indicates a non-sparking condition and 8 indicates a highest sparking condition. As seen from Fig. 7, as the inductance of the inductive shunt is increased, the commutation performance is remarkably improved. Assuming that the practically acceptable spark numbers are 3 to 8, the inductance of larger than 2 mH is sufficient. The inductance of the main pole under this condition is approximately 10 mH. By providing the inductive shunt having the inductance which is larger than 20% of the inductance of the main pole winding, the commutation performance in the pulsating current operation of the vehicle motor can be substantially improved. As described hereinabove, according to the present invention, the inductive shunt having the inductance which is larger than 20% of the inductance of the main pole winding is connected in parallel with the main pole winding. Accordingly, the vehicle motor having an improved commutation performance in the pulsating current operation is provided.

Claims: WHAT IS CLAIMED IS: 1. A motor for a vehicle driven by a pulsating current, characterized by an inductive shunt (9) connected in parallel with a main pole winding (7), said inductive shunt having an inductance larger than 20% of an inductance of said main pole winding. 2. A D.C. series motor for a vehicle characterized by an armature (5); an interpole winding (6) connected in series with said armature; a main pole winding (7) connected in series with said interpole winding; a resistive shunt (8) connected in parallel with said main pole winding for shunting a pulsating current flowing through said main pole winding when said motor is operated by a pulsating current; and an inductive shunt circuit (9, 10, 11) connected in parallel with said main pole winding, said inductive shunt circuit having an inductive shunt (9) having an inductance larger than 20% of an inductance of said main pole winding, a field control resistor (16) connected in series with said inductive shunt and a mechanical switch (11) connected in series with said resistor. 3. In a combination of rolling stocks having a pantagraph (1) slidably engaging with a stringing for supplying a single phase A.C. power, a single phase transformer (2) having a primary winding connected to said pantagraph, a full-wave rectifier (3) connected to a secondary winding of said transformer and a filtering reactor (4) connected to an output terminal of said rectifier for supplying a pulsating current; and a D.C. motor (20) driven by the pulsating current for driving said vehicle; characterized by that said D.C. motor includes an inductive shunt (9) connected in parallel with a main pole winding thereof, said inductive shunt having an inductance larger than 20% of an inductance of said main pole winding.

Inventors: ISHIKAWA, YOSHIHISA
Applicants: HITACHI, LTD.
Application year: 1982
Main classification: H02K23
IPC codes: B60L9, H02K23