Some applications want the motor to run exactly when the power is on — no button press, no keypad entry. A solar pump, a remote irrigation valve, a fan that must restart by itself after a storm, or a cabinet you cannot reach. There are two distinct questions here, and they are wired differently:
- Run on power-on — the drive starts the motor the moment power is applied (a run command is already present).
- Auto-restart after a power loss — the drive drops out on a trip or supply interruption, then restores itself when power returns.
Both are supported on the SHZK 300N, but they need different setups. This guide covers them from our test bench.
1. Run the motor on power-on (terminal-based auto-start)
The simplest way to make a SHZK 300N start immediately at power-on is to keep a permanent run command on the digital input. This is really just external-terminal control (P0-02 = 1) with a closed DI that is always present.
Wiring
- Take a short wire and connect one end to terminal GND.
- Connect the other end to terminal DI1 (forward run).
- Assuming the frequency source is already set (keypad, AI1, or communication), the drive runs whenever power is applied.
Parameter
Keep the run-command source on terminals:
| Parameter | Value | Purpose |
|---|---|---|
| P0-02 | 1 | Terminal operation command |
With GND permanently tied to DI1, the drive starts the motor as soon as it energises and stops when power is removed. For an inverted (reversing) start, tie GND to DI2 instead and set the direction parameter accordingly.
2. Auto-restart after a power loss or transient trip
For a supply interruption or a brief line dip, you usually do not want a permanent closed contact — you want the drive to detect the loss and restart automatically once the supply is stable. Configure this through the fault-restart / restart-after-fault settings so the drive attempts to restart after an undervoltage or supply-loss event, within safe limits.
- Enable automatic restart after fault and set a reasonable number of restart attempts.
- Set a short restart delay so the drive does not hammer back on before the supply and motor are stable.
- Pair this with the flying restart / speed search feature so the drive re-synchronises to an already-spinning load instead of stopping it.
Because the exact parameter group for restart attempts and restart delay varies by firmware revision, check the current 300N manual for the restart group before commissioning.
3. Which method should you use?
| Situation | Recommended |
|---|---|
| Solar pump that must run whenever the sun is up | Power-on start (permanent DI closed) |
| Mains-fed pump that should return after a brief outage | Auto-restart-after-fault + speed search |
| Simple end-of-line fan or conveyor that just needs to come back | Either — depend on whether a restart delay is acceptable |
| Anything that people service while energized | Do not use auto-restart without a guard/estop |
From our test bench
We full-load test every 300N before shipping, including the power-on start and restart behaviour, so the wiring above is the same method we use on our own production and test pumps. If your pump must restart unattended at a specific pressure, start with the constant-pressure PID setup and combine it with the restart setting above.
Related Technical Guides
- VFD Wiring Guide — DI/GND terminal run commands
- VFD Flying Restart & Speed Search
- VFD Fault Codes — clearing and restarting after trips
- Constant Pressure Water Supply Setup
- VFD Parameter Setup
Need a restart plan matched to your pump or fan? Contact our application engineers.