Many machines need to run at several fixed speeds — a washer that fills, washes and spins; a conveyor that jogs then runs; a machine tool with roughing and finishing feeds. Instead of changing an analog signal each time, a SHZK 300N can store preset speeds and select them from digital inputs using multi-speed control, or run a whole timed sequence automatically with the built-in simple PLC. This guide explains both, using the real P0 and PC-group parameters.
How multi-speed selection works
You assign digital inputs the “multi-speed command” function. Each input acts as one bit, so the open/closed combination of the inputs is a binary number that picks one preset. Three inputs select up to 8 speeds (2³), four inputs up to 16 (2⁴). The presets themselves are the PC-00, PC-01… values, set as a percentage of the maximum frequency, range –100 % to 100 %.
Setting up multi-speed control
- Set the frequency source to multi-speed: P0-03 = 6.
- Configure the required digital inputs in the P4 group to the multi-speed function (these are the “Multi-speed Command 1, 2…” terminals shown on the control diagram).
- Enter each target speed in PC-00, PC-01… as a percentage. For example with a 50 Hz maximum, PC-01 = 40 % gives 20 Hz.
- Wire your selector switches or PLC outputs to the chosen inputs. Each unique combination selects the matching preset.
- Give a run command from keypad, terminals or comms; the drive runs at the selected speed.
| Parameter | Meaning | Range |
|---|---|---|
| P0-03 = 6 | Frequency source = multi-speed | — |
| P4-xx | Assign DI to multi-speed command bits | — |
| PC-00–PC-09… | Preset speed instructions | –100.0–100.0 % |
Negative percentages select reverse rotation, which is handy for a forward/reverse cycle selected by the same inputs. Use U0-17 (PLC/multi-speed stage) to confirm on the display which speed is currently active — it is the quickest way to verify your bit wiring.
Running an automatic timed sequence — simple PLC
When the machine must move through speeds on its own with no external selector, set the frequency source to P0-03 = 7 (simple PLC). The drive then steps through preset stages automatically, each for its own run time:
- PC-00… — the speed (as %) of each stage, in order.
- PC-26, PC-28, PC-30, PC-32… — the run time of stages 4, 5, 6, 7… in seconds or hours (0.0–6553.5), including the earlier stages.
- PC-27, PC-29, PC-31, PC-33… — choose which acceleration/deceleration time each stage uses (0–3), so a slow approach can use a long ramp and a fast move a short one.
You can set whether the sequence runs once and stops, or repeats continuously, through the simple-PLC mode option. Watch U0-17 to see the stage advance while commissioning.
Which to use — multi-speed or simple PLC?
Operator or PLC picks each fixed speed on demand. Best when the next step depends on a person or an external condition.
Drive cycles through a fixed timed recipe by itself. Best for repeatable automatic sequences with no operator.
Common mistakes
- Wrong speed selected: the bit order of the inputs is reversed — confirm which DI is the least-significant bit and check U0-17.
- Speed stays at zero: P0-03 was not set to 6/7, or the presets were left at 0 %.
- Sequence will not repeat: the simple-PLC run mode is set to “run once”; change to continuous.
From our test bench
When a customer needs an automatic cycle we always commission it in two passes: first on multi-speed with manual switches to prove every preset and its wiring, then switch to simple-PLC mode for the timed sequence. Separating “are the speeds correct” from “is the timing correct” makes a problem easy to locate instead of debugging both at once.
Related Technical Guides
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