Integrated Servo Fails to Enable Due to Recurring Undervoltage
Posted: Sat Oct 10, 2026
Hello everyone, I’ve encountered an issue with cold-start operation.
I am using an integrated servo motor (https://www.oyostepper.es/category-81-b ... grado.html) in automation equipment for a cold storage facility. When powered on in a -30°C environment, the drive repeatedly reports a "DC bus undervoltage" error, preventing the motor from enabling. However, if I use a heat gun to warm the rear of the motor for half a minute before powering it up, it operates normally.
Upon inspection, I found that the ESR (Equivalent Series Resistance) of the internal DC bus electrolytic capacitors increases several-fold at low temperatures. This limits the charging current at the moment of power-up, causing the bus voltage to build up too slowly and triggering the undervoltage protection. Replacing them with solid-state capacitors improved the situation, but those are limited in terms of capacitance and voltage rating.
I would like to ask for advice on selecting bus capacitors for integrated servos in low-temperature environments. Should I implement a pre-heating circuit, or switch to wide-temperature-range capacitors?
Thanks in advance for any help or guidance you can provide.
I am using an integrated servo motor (https://www.oyostepper.es/category-81-b ... grado.html) in automation equipment for a cold storage facility. When powered on in a -30°C environment, the drive repeatedly reports a "DC bus undervoltage" error, preventing the motor from enabling. However, if I use a heat gun to warm the rear of the motor for half a minute before powering it up, it operates normally.
Upon inspection, I found that the ESR (Equivalent Series Resistance) of the internal DC bus electrolytic capacitors increases several-fold at low temperatures. This limits the charging current at the moment of power-up, causing the bus voltage to build up too slowly and triggering the undervoltage protection. Replacing them with solid-state capacitors improved the situation, but those are limited in terms of capacitance and voltage rating.
I would like to ask for advice on selecting bus capacitors for integrated servos in low-temperature environments. Should I implement a pre-heating circuit, or switch to wide-temperature-range capacitors?
Thanks in advance for any help or guidance you can provide.