Otis SKY-2 Error Code 300

Otis Elevator Critical Controller

Model: SKY-2 | Code: 300

Applicable Systems
SKY-2

Symptoms

The Otis SKY-2 drive controller displays fault code 300 indicating DC BUS OVER voltage. The DC bus voltage has exceeded 108% of the rated 750V, reaching 810V or higher. The drive will shut down immediately to protect the IGBT power modules and DC bus capacitors from overvoltage damage.

Possible Causes

  • Regenerative energy from elevator deceleration exceeding brake resistor capacity
  • Brake chopper unit failure or brake resistor open circuit
  • Input AC line voltage too high causing elevated DC bus
  • DC bus capacitor degradation reducing ripple absorption capacity

Troubleshooting Steps

  1. Step 1: Read fault code 300 on drive controller display
    Code 300 displayed, DC bus voltage shown above 810V threshold
  2. Step 2: Measure actual DC bus voltage with DC voltmeter across bus terminals
    Voltage reading confirms overvoltage condition
  3. Step 3: Inspect brake chopper and brake resistor for continuity and damage
    Brake resistor within specification, chopper transistor switching properly
  4. Step 4: Verify AC input line voltage is within nominal range
    AC input voltage at or below nominal rated voltage

How to Reset

To reset: 1) Fix the DC bus overvoltage cause. 2) Power cycle the drive controller. 3) Verify fault clears and elevator returns to service. Caution: Do not reset without investigating the cause; repeated overvoltage can destroy IGBT modules.

Common Replacement Parts

  • Otis Brake Resistor: SKY-2 Drive Brake Resistor Assembly (Match to drive power rating)

Frequently Asked Questions

  • Q: Why does the DC bus voltage rise during deceleration?

    When the elevator decelerates, the motor acts as a generator, feeding energy back into the DC bus. The brake chopper and resistor dissipate this energy. If the resistor or chopper fails, bus voltage rises rapidly.

  • Q: Can I increase the overvoltage threshold to prevent nuisance trips?

    No. The 810V threshold is set to protect the IGBT modules and capacitors. Increasing it risks catastrophic component failure. Instead, fix the regenerative energy dissipation path.

Related Otis Fault Codes

Source: Otis SKY-2 Drive Fault Code Manual (1lift.cn), Otis 21VF/MCS321 Fault Code Manual

Category: Elevator