Heating Solutions for Electric Vehicles
1.Electric heating method
1.1 The concept and functional principle of PTC
Most electric heating methods use PTC heating. PTC is the abbreviation of Positive Temperature Coefficient, which means a positive temperature coefficient, and generally refers to semiconductor materials or components with a large positive temperature coefficient. Usually the PTC we refer to refers to a positive temperature coefficient thermistor, referred to as a PTC thermistor. PTC thermistor is a typical temperature-sensitive semiconductor resistor. When it exceeds a certain temperature (Curie temperature), its resistance value increases sharply with the increase of temperature. That is, the power of the PTC heater will be suddenly reduced to a minimum value, bringing the temperature back below its Curie temperature. Because of this feature, the PTC heater has the advantages of constant temperature heating, no open flame, and long service life.
1.2 Low-voltage wind heating
1.2.1 Implementation plan
A water pump, water pipe, three-way valve, heater core, motor, and radiator tank are added to the engine room to form a closed water circulation system, and a low-voltage air heater is added to the HVAC structure.
When the heating switch of the air-conditioning controller is turned on, the three-way valve B changes the direction of the coolant, so that the coolant passes through the heater core. According to the control temperature of the temperature sensor in the car, the temperature inside the car, the temperature of the water pump, and the control of the three-way valve A Temperature, coolant temperature to control the working state of PTC and heater core. When the heating switch of the air conditioner controller is turned off, the three-way valve B changes the direction of the coolant again so that the coolant does not pass through the heater core.
1.2.2 Advantages
Since the heater core uses the waste heat of the coolant, the power output of the low-voltage air heater can be saved, and part of the motor cooling function is shared, reducing the power output of the radiator tank.
1.2.3 Disadvantages
1) The amount of modification to the used parts is relatively large, and the modification cost is relatively high.
2) The use of low-voltage air-heating heaters requires a certain rectification space for the lower part of the original car air-conditioning heater, but adding a PTC auxiliary heating device will change the shell of the heater blower assembly. To increase the PTC auxiliary device under the heating heater core, the air duct at the bottom of the housing and the air duct for blowing feet should all be moved down.
3) It is necessary to change the control circuit again, add control components and some pipelines, so that the controller can control the water pump and the three-way valve, the control is complicated, and the cost increases a lot.
4) The PTC is arranged in the cockpit, which has certain potential safety hazards.
