JP2000255254A5 - - Google Patents

Description

When a high voltage battery of about 100 to 300 V is used as the power battery, the power battery 15b is insulated from the vehicle body as shown in FIG. 7. This is from the aspect of safety to the human body due to electric shock or the like. Further, the closed container 21b of the electric compressor 21 is grounded to the vehicle body. Therefore, when the winding 21a is short-circuited to the closed container 21b due to poor insulation of the winding 21a of the electric compressor, the high voltage side of the power battery 15b is moved to the vehicle body. Is short-circuited, and a short-circuit current (hereinafter referred to as "ground fault current") flows. This ground fault current is a small current in the case of FIG. 7, but it may lead to equipment failure or the like . Therefore, in general, a ground fault detection circuit for detecting this ground fault current is provided, and when the ground fault current is detected, the current cutoff means is activated to cut off the ground fault current. In FIG. 7, ground fault detection circuits 41a and 41b are provided on the anode and cathode terminals of the power battery 15b, respectively, and when the ground fault detection circuits 41a and 41b detect a ground fault current, the breaker 43a is a current blocking means. , 43b is operated to protect the air conditioner and the like from the ground fault current. Since the resistance in the ground fault detection circuits 41a and 41b has a very large resistance value, the ground fault through this resistance is designed so as not to cause a safety problem.

However, as shown in FIG. 7, since the conventional current detection circuit 35b is provided on the cathode side, that is, the ground potential side of the power battery 15b, the ground is ground in a hybrid vehicle that employs a voltage of about 36V as the power battery. The entangled current does not pass through the current detection circuit 35b. Therefore, a short circuit (ground fault) between the winding 21a of the electric compressor and the closed container 21b is not detected. When a ground fault occurs, the battery 15b is short-circuited, and a large current causes a malfunction of various devices due to a sudden drop in the voltage of the battery 15b. Therefore, in a hybrid vehicle that uses a voltage of about 36V as a power battery, this is used. Protective measures against ground fault current are required.

The present invention has been made to solve the above problems, and an object of the present invention is to be used in a hybrid vehicle equipped with a low voltage battery by switching or coordinating a plurality of power sources to drive wheels. In the protection circuit of the air conditioner, the protection of the electric compressor etc. is further improved with a simple configuration and surely from the abnormal current such as the ground fault current without separately providing the ground fault detection circuit and the breaker as described in the prior art. The purpose is to provide a protection circuit.

Further, an abnormal current such as a ground fault current is a large current . Therefore, the control unit 33 monitors the current flowing into the electric compressor 21 and controls the operation of the DC conversion circuit 31 so as to limit the current value flowing into the electric compressor 21 when an abnormal current is detected. That is, when the control unit 33 detects a ground fault current, an interphase short-circuit current, or an overcurrent due to load fluctuation, the control unit 33 flows to the inverter device 23 or the like in order to protect the inverter device 23a, the electric compressor 21, or the like from these abnormal currents. The switching operation of the DC / AC conversion circuit 31 is controlled so as to limit the current.

As shown in FIG. 5, since the ground fault current does not pass through the ground line 24b, it is not detected by the current detection circuit 35. Therefore, the occurrence of a ground fault is detected by the voltage change detection circuit 37. That is, when a ground fault occurs, both terminals of the power system battery 15 are short-circuited, and the voltage between the terminals of the power system battery 15 drops sharply. From this point, by monitoring the change in the output voltage of the power system battery 15 by the voltage change detection circuit 37, it is possible to detect that a ground fault has occurred when the voltage drops sharply.

As described above, according to the protection circuit of the air conditioner in the above embodiment, in a hybrid vehicle equipped with a power system battery of about 36 V, a ground fault current, an interphase short circuit current, an overcurrent due to overload, etc. can be achieved with a simple circuit configuration. Abnormal currents can be detected, and protection of electric compressors and the like can be improved from these abnormal currents. Further, the protection circuit according to the present invention is not limited to the air conditioner in the hybrid vehicle, and is an electric vehicle that uses a battery independent of the battery that drives the traveling motor as a power source for the air conditioner, and a gasoline vehicle that drives the air conditioner with the battery. The same applies to those air conditioners.

0031
【Effect of the invention】
According to the protection circuit of the electric compressor used in the automobile air conditioner of the present invention, when a battery of about 36 V is mounted and the electric compressor of the air conditioner is driven by using the power of this battery, the circuit configuration is simple. Since the entanglement current can be detected and cut off, it is possible to improve the protection of the electric compressor and the like from the ground fault current.