Heater Relay Coil Voltage Checking to Avoid Inverter EMI Misdiagnosis
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Solution Overview
Problem
In electric vehicles, the electromagnetic interference (EMI) signals generated by the inverter can cause misdiagnosis of the heater due to AC noise affecting the heater relay coil, leading to erroneous diagnosis of the heater's status.
Innovation Solution
A battery apparatus with a processor-controlled heater system, including a relay and heating resistor, that diagnoses the heater by detecting voltages at the relay coil terminals using different voltage levels to differentiate between normal operation and EMI-induced errors, enabling accurate diagnosis of driver failures and EMI interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the inverter increases switching frequency and current consumption to quickly drive the motor, then the motor response speed is improved, but electromagnetic interference signals are generated that cause misdiagnosis of the heater
Solution Approach 1:
The system performs preliminary diagnosis of the heater by detecting relay coil voltage before the inverter operates. This preliminary action captures the heater's baseline status before EMI interference occurs during high-speed motor operation, allowing accurate diagnosis without being affected by subsequent electromagnetic interference
Solution Approach 2:
The diagnosis system proactively detects and identifies EMI interference patterns before they can cause misdiagnosis. By detecting abnormal voltage fluctuations caused by EMI in advance, the system can distinguish between actual heater faults and EMI-induced false readings, preventing erroneous diagnosis
2Productivity
If the heater relay coil is subjected to AC noise from the inverter, then the motor can be driven at high speed, but the heater status diagnosis becomes erroneous
Solution Approach 1:
The system diagnoses the heater by measuring relay coil voltage before the inverter is activated. This timing ensures that the measurement is performed when no EMI is present, guaranteeing diagnosis accuracy while allowing the inverter to operate at full capability for motor driving
Solution Approach 2:
The relay coil voltage serves as an intermediary indicator for heater status. Instead of directly measuring the heater element which would be exposed to EMI, the system measures the voltage at the relay coil terminals, which provides indirect information about heater status without being corrupted by electromagnetic interference
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables accurate diagnosis of the heater's status by distinguishing between normal voltage readings and those affected by EMI or driver failures, preventing erroneous diagnoses and ensuring proper operation of the heater.
Implementation Method 1
a relay switch and a relay coil configured to drive the relay switch
Implementation Method 2
a heater connected between a positive terminal and a negative terminal of the battery pack... a heating resistor
Data Source
Figure 1
Figure 2
Figure 3~5
AI summary
A processor of a battery apparatus detects voltages of a first terminal and a second terminal of a relay coil included in a relay before closing the relay to operate the heater, and diagnoses the heater based on a voltage which the voltage of the first terminal and the voltage of the second terminal correspond to among a high voltage and a low voltage for driving the relay, and a voltage for diagnosis.