Frequency inverter · Quick Start Guide

Multi-speed operation INVT GD28

Call up fixed speeds via switches or a PLC, without a potentiometer or analog signal: you store up to 16 steps in the drive and select them via digital inputs. Ideal for conveyors, pumps and fans with fixed operating points.

Before connecting

Disconnect all supplies and wait at least 5 minutes (manual, all GD28 models). Only then open the cover and touch the terminals.
The digital inputs work with 10–30 V DC (high level). Never apply mains voltage to the control terminals.
STO is bridged at the factory and therefore inactive. Using STO as a safety function requires a risk assessment and acceptance test.

1Set the frequency source to multi-step speedRequired
The drive separates two questions: where does the run command come from (P00.01), and where does the frequency come from (P00.06)? For multi-speed operation you change the frequency source. Digital inputs then select one of the stored steps.
If switches or a PLC are to start the motor, set P00.01 to 1. With the factory default 0 you start on the keypad with RUN; the terminals then only select the frequency.
Parameter Value Meaning
P00.06 8 Frequency reference A = multi-step speed running (factory default 0 = P00.10)
P00.01 1 Run command source = terminal (factory default 0 = keypad)
According to the manual (chap. 6.4.2.5), multi-step selection takes priority over keypad, analog input, pulse input, PID and communication as soon as one of the multi-step terminals is ON.
Source: GD28 Manual V1.3 chap. 6.4.2.5; vfd-konfig gd28/01-basis-P00-P02 (P00.01, P00.06)

Parameter	Value	Meaning
P00.06	8	Frequency reference A = multi-step speed running (factory default 0 = P00.10)
P00.01	1	Run command source = terminal (factory default 0 = keypad)

2Assign digital inputs as multi-reference terminalsRequired

Each multi-step terminal is one bit. One terminal selects between two steps, two between four, three between eight, four between 16.

The GD28 has four digital inputs DI1–DI4 and the high-speed input HDI1, which can also work as a normal digital input. Here DI1 stays forward run and the multi-step terminals follow in order: DI2, DI3, DI4 and HDI1. DI2 and DI3 are forward jog and fault reset by default and are reassigned for this. The parameters of group P05 can only be changed at standstill.

Parameter	Value	Meaning
P05.01	1	DI1 = forward run (factory default, keep)
P05.02	16	DI2 = multi-step terminal 1 → 2 steps (instead of forward jog)
P05.03	17	DI3 = multi-step terminal 2 → 4 steps (instead of fault reset)
P05.04	18	DI4 = multi-step terminal 3 → 8 steps
P05.00	1	HDI1 works as a digital input (factory default 0 = pulse input)
P05.11	19	HDI1 = multi-step terminal 4 → 16 steps

How many multi-reference terminals do you need?

Steps	Terminals	Function values	Inputs
2	1	16	DI2
4	2	16, 17	DI2, DI3
8	3	16, 17, 18	DI2–DI4
16	4	16, 17, 18, 19	DI2–DI4, HDI1

Reverse needs no terminal of its own: a negative step value (down to −300 %) reverses the direction for that step. P00.13 = 2 disables reverse.

After reassigning DI3, reset faults on the keypad with STOP/RST.

DI5–DI8 in group P05 are virtual inputs without a terminal; they are set via communication (P05.16).

By default the NPN/PNP slide switch is set to PNP: the contact is wired between +24V and DIx or HDI1.

Show wiring “Preset speeds via switches”

Source: GD28 Manual V1.3 chap. 6.4.2.5; vfd-konfig gd28/02-io-P05-P06 (P05.00–P05.16, function list), gd28/10-klemmen (DI, HDI1, NPN/PNP), gd28/06-schutz-P08-P11 (sign), gd28/01-basis-P00-P02 (P00.13)

3Enter the step valuesRequired

The steps are in group P10, in every second parameter: step 0 in P10.02, step 1 in P10.04, step 2 in P10.06 up to step 15 in P10.32. The parameters in between (P10.03, P10.05 …) are the run times of the simple PLC. For selection via terminals the manual only describes the frequency values.

The value is a percentage of the maximum frequency P00.03: 100.0 % corresponds to P00.03, 50.00 Hz by default. The range is −300.0 to 300.0 %; every step is 0.0 % by default. You can change the values while running.

Parameter	Value	Meaning
P10.02	z. B. 0.0 %	Step 0: applies when all multi-step terminals are OFF
P10.04	z. B. 40.0 %	Step 1 → 20.00 Hz (calculated, P00.03 = 50.00 Hz)
P10.06	z. B. 60.0 %	Step 2 → 30.00 Hz (calculated)
P10.08	z. B. 100.0 %	Step 3 → 50.00 Hz (calculated)
P10.10–P10.32	as required	Steps 4–15, every second parameter

Conversion (calculated): value in % = required frequency × 100 ÷ P00.03. Example: 35 Hz with P00.03 = 50.00 Hz → 70.0 %.

Above 100 % only works if P00.03 and the upper limit P00.04 (50.00 Hz by default) are set higher. If the step exceeds P00.04, the drive runs at P00.04.

Step 0 is 0.0 % by default. With a run command and all terminals OFF the motor therefore runs at 0 Hz.

Source: vfd-konfig gd28/06-schutz-P08-P11 (group P10, table step/speed/time), gd28/01-basis-P00-P02 (P00.03, P00.04); GD28 Manual V1.3 chap. 6.4.2.5

4Which terminals select which step?Required

The multi-step terminals form a binary number; according to the manual terminal 1 is the least significant bit: terminal 1 counts 1, terminal 2 counts 2, terminal 3 counts 4, terminal 4 counts 8. The sum of the terminals that are ON is the step. Example: terminals 1 and 3 ON → 1 + 4 = step 5 (P10.12).

Try it right in the table: tap the terminals and the matching step is highlighted. The simulator calculates the frequency with P00.03 = 50.00 Hz.

Terminal combinations (ON = input active; factory default P05.14)

Step	Terminal 4 (19)	Terminal 3 (18)	Terminal 2 (17)	Terminal 1 (16)	Value in
0	OFF	OFF	OFF	OFF	P10.02
1	OFF	OFF	OFF	ON	P10.04
2	OFF	OFF	ON	OFF	P10.06
3	OFF	OFF	ON	ON	P10.08
4	OFF	ON	OFF	OFF	P10.10
5	OFF	ON	OFF	ON	P10.12
6	OFF	ON	ON	OFF	P10.14
7	OFF	ON	ON	ON	P10.16
8	ON	OFF	OFF	OFF	P10.18
9	ON	OFF	OFF	ON	P10.20
10	ON	OFF	ON	OFF	P10.22
11	ON	OFF	ON	ON	P10.24
12	ON	ON	OFF	OFF	P10.26
13	ON	ON	OFF	ON	P10.28
14	ON	ON	ON	OFF	P10.30
15	ON	ON	ON	ON	P10.32

Source: GD28 Manual V1.3 chap. 6.4.2.5 and function list P05 (terminal 1 = LSB); vfd-konfig gd28/06-schutz-P08-P11

5First run and troubleshootingRequired

Complete all items before the first start. Motor data, auto-tuning and STO are covered by the commissioning guide on the GD28 support page.

Motor data from the rating plate entered in group P02
P00.06 = 8 set, for start via terminals also P00.01 = 1
Multi-step terminals assigned: DI2 = 16, as required DI3 = 17, DI4 = 18 and HDI1 = 19 (with P05.00 = 1)
Values entered in P10.02, P10.04 …, every second parameter
Contacts wired between +24V and DIx (PNP, factory default), STO jumper fitted
At standstill, every required terminal combination switched, DI status checked in P17.12 and reference frequency in P17.00

If the wrong step is selected

Observation	Cause	Remedy
Frequency does not match the step	Value entered in a run-time parameter (P10.03, P10.05 …)	Step n is in P10.(2 + 2n): step 1 = P10.04, step 5 = P10.12
HDI1 does not switch a step	HDI1 is still a pulse input	Set P05.00 = 1, function in P05.11
Input does not react to the wire	Terminal is set to virtual	Check P05.16, factory default 0x000
Input does not react, wiring is correct	NPN/PNP switch does not match the wiring	PNP: contact from +24V to DIx; NPN: from DIx to COM
Step permanently higher than expected	An input is active unintentionally	Read the DI status in P17.12 (bit 0–3 = DI1–DI4, bit 10 = HDI1)
Terminal acts inverted	Polarity inverted	Check P05.14, factory default 0x000
Motor turns in the wrong direction	Negative step value or P00.13	Check the sign of the step, P00.13 (factory default 0)
Display shows E40, motor does not run	STO active: STO jumper missing	Check the factory jumper +24V–STO1–STO2, details on the support page

Source: vfd-konfig gd28/02-io-P05-P06 (P05.00, P05.14, P05.16), gd28/08-monitor-P17-P29 (P17.00, P17.12), gd28/10-klemmen, gd28/01-basis-P00-P02 (P00.13); STO fault code E40 according to vfd-konfig

Revision 2.0 · 26.09.2026 · Source: INVT GD28 Series VFD Manual V1.3 (03/2026), chap. 6.4.2.5 and parameter groups P00, P05, P10, P17; prepared in spstiger vfd-konfig (gd28/01-basis-P00-P02, 02-io-P05-P06, 06-schutz-P08-P11, 08-monitor-P17-P29, 10-klemmen). The manufacturer manual and applicable standards take precedence; installation and commissioning by a qualified electrician only.

Everything else for your drive

Interactive wiring diagram, step-by-step commissioning, keypad simulator and downloads:

Open the INVT GD28 support page

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INVT GD28 frequency inverter with STO and optional communication card

If you need a compact frequency inverter with built-in STO, brake chopper and EMC filter that can be integrated into PROFINET, EtherCAT, EtherNet/IP or Modbus TCP when required, the INVT GD28 is a universal inverter from 0.2 to 2.2 kW for single-phase 230 V and 0.4 to 22 kW for three-phase 400 V. Modbus RTU comes as standard; a single card covers all Ethernet fieldbuses: the EC-TX149. 🏭 Typical Applications Packaging, printing and machine tools: STO to SIL 3 / PL e is built into every model. According to INVT, sensorless vector control delivers up to 200 % starting torque at 0.5 Hz, with a torque response below 10 ms. Pumps, fans and compressors: integrated PID controller, energy-saving control at partial load and speed tracking for a smooth restart of a coasting motor. In light-duty mode, one unit covers the next larger motor rating. Conveyors, mixers and filling machines: linear or S-curve ramps, up to 16 preset speeds and ride-through during short mains dips. Plants with different fieldbuses: The EC-TX149 handles PROFINET, EtherCAT, EtherNet/IP and Modbus TCP — the protocol is selected by parameter. One card type in stock instead of four. ⚙️ Control and Functions Two control modes: V/f control and sensorless vector control (SVC) with a speed range of 1:100 and ±0.2 % speed accuracy. Asynchronous and permanent-magnet synchronous motors, autotuning of motor parameters. Dual rating: heavy duty 150 % for 60 s and 180 % for 10 s, light duty 110 % for 60 s and 150 % for 10 s. Output frequency 0–599 Hz, frequency resolution 0.01 Hz. Frequency setpoint via keypad, potentiometer, analog input, pulse input, preset speeds, PID or Modbus — setpoint channels can be combined. Motor temperature monitoring: PTC directly on DI4, PT100, PT1000 or KTY84 via the AO→AI analog combination. Fewer nuisance trips: overvoltage and overcurrent stall control, automatic voltage regulation (AVR). 🔌 Connections and Control I/O 5 digital inputs: 4 standard inputs and 1 high-speed input up to 50 kHz, NPN and PNP (factory setting PNP). 2 analog inputs: AI1 0–10 V or 0–20 mA, AI2 −10–+10 V or 0–20 mA. 1 analog output 0–10 V or 0–20 mA and 1 high-speed digital output up to 50 kHz. 1 relay output: changeover contact, 250 V AC / 3 A or 30 V DC / 1 A. RS-485 with Modbus RTU as terminal, RJ45 for the external keypad. USB-C: parameter setting, parameter copy and monitoring with the INVT Workshop software — the PC powers the control electronics, no mains voltage and no interface converter needed. Spring-clamp terminals for the control wiring, one slot for expansion cards. ⚠️ Before Ordering Select by output current, not by kW: The motor rated current must match the inverter's output current. The kW figure in the model name applies to heavy duty and a standard four-pole motor. EMC filter: With the built-in filter, the single-phase models meet category C2, the three-phase models C3. C2 on three-phase units requires an external filter. External brake resistor: The brake chopper is built in; the resistor is connected to (+)/PB. Do not go below the minimum resistance for each power rating. Using STO: The STO inputs are jumpered at the factory. If STO is part of your safety concept, remove the jumpers and wire a safety relay or safety PLC. Keypads: A simple LED keypad is built in. For the cabinet door, the BOP-270 (LED) and SOP-28 (LCD) keypads are available. While a USB-C cable is plugged in, the external keypad is disabled. 🔧 Frame Sizes, Environment and Mounting Frame A (230 V: 0.2–0.75 kW · 400 V: 0.4–1.1 kW): 60 × 190 × 155 mm, approx. 1.25 kg, fanless Frame B (230 V: 1.1–2.2 kW · 400 V: 1.5–4 kW): 70 × 190 × 155 mm, approx. 1.3 kg Frame C (400 V: 5.5–7.5 kW): 90 × 235 × 155 mm, approx. 2.1 kg Frame D (400 V: 11–15 kW): 130 × 250 × 185 mm, approx. 3.55 kg Frame E (400 V: 18.5–22 kW): 160 × 300 × 190 mm, approx. 4.9 kg Mounting: wall mounting with two screws (A/B), DIN rail with the AP-RB-A-01 adapter (A/B), flange mounting with the heat sink outside the cabinet (C/D/E). Below 40 °C ambient temperature, units may be mounted side by side without clearance. IP20. Operation −10 °C to +50 °C (heavy duty without derating), storage −20 °C to +70 °C, humidity below 95 % non-condensing, above 1000 m 1 % derating per 100 m. Coated PCBs to 3C2/3S2. 🏷️ Manufacturer and Reliability INVT Electric from Shenzhen is one of the major Chinese manufacturers of drive technology. The GD28 is certified to CE, UL and TÜV; all models reach efficiency class IE2. INVT frequency inverters are in productive use at numerous spstiger customers — with support in German directly from us.

Input voltage

230 V AC 400 V AC

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