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Motor Temperature Sensor

Introduction

Temperature sensors in motors are the ideal way to monitor the motor's health and avoid over-temperature damage to the motor and its components.

Wiring

Thermistors can be wired to any of the analog inputs (Throttle/Analog Input 1, Brake1/Analog Input 2, Brake2/Analog Input 3 or ABMS/Analog Input 4) depending on whether an NTC or PTC thermistor is used.

Note

Firmware version 6.022 and below can only have NTC temperature sensors and wired to Brake2/Analog Input 3.

For NTC (resistance decreases with temperature increase)

NTC thermistor wiring to Brake2 for motor temperature

For PTC (resistance increases with temperature increase)

PTC thermistor wiring to Throttle for motor temperature

Configuration

  1. Enable Features bit 5 Motor temp sensor enable.

  2. Select the Motor temperature source.

  3. Enter the motor temperature sensor voltage for each of the following:

    1. Temperature feedback V at 0 °C

    2. Temperature feedback V at 25 °C

    3. Temperature feedback V at 50 °C

    4. Temperature feedback V at 75 °C

    5. Temperature feedback V at 100 °C

    6. Temperature feedback V at 125 °C

The thermistor datasheet can be used to estimate the motor temperature sensor voltage for each temperature.

Thermistor Voltage Calculator

Note

The temperatures outside of 0 °C through 125 °C are linearly extrapolated for temperatures above 125 °C and below 0 °C.

Brake1 or 2 to Hall Ground formula

If tying the sensor from Brake 1/Analog input 2 or Brake 2/Analog input 3 to Hall ground, on a motor with Hall position sensors, this formula can be used to better estimate the motor temperature sensor voltage for each given sensor temperature resistance (Rtherm).

Temperature feedback V at C = (4750*(172268*(Rtherm^2) + 13913806737*Rtherm + 828480786525))/(807*(253*Rtherm + 20419350) *(1417*Rtherm + 5823153))

Troubleshooting

  • There are a lot of fluctuations in my motor temperature

    If using the Hall ground, the thermistor output can be affected by high frequency noise resulting in fluctuations in the temperature readings

  • How can I test if my voltage values are correct?

    The simplest way to test the accuracy of the temperature feedback involves using a hand-held thermometer and two known temperatures such as ice water and boiling water following the steps below. Verify motor temperature in BACDoor® matches the expected temperature on your thermometer, i.e. ~0 °C for ice water or ~100 °C for boiling water.