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MICROMASTER 420s are a range of frequency inverters for controlling the speed of three phase AC motors. The various models available range from the 120 W single-phase input to the 11 kW three-phase input.

The inverters are microprocessor-controlled and use state-of-the-art Insulated Gate BipoIar Transistor (IGBT) technology. This makes them reliable and versatile. A special pulse-width modulation method with selectable Pulse frequency permits quiet motor operation. Comprehensive protective functions provide excellent inverter and motor protection.

The MICROMASTER 420 with its default factory settings, is ideal for a large range of simple motor control applications. The MICROMASTER 420 can also be used for more advanced motor control applications via its comprehensive parameter lists.

The MICROMASTER 420 can be used in both ‘stand-alone’ applications as well as being integrated into ‘Automation Systems’.

Micromaster 420
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Siemens Micromaster 420 Features


Main Characteristics
Easy installation
Easy commissioning
Rugged EMC design
Can be operated on IT line supplies
Fast repeatable response time to control signals
Comprehensive range of parameters enabling configuration for a wide range of
Simple cable connection
1 Output relay
1 Analog output (0 – 20 mA)
3 Isolated and switchable NPN/PNP digital inputs
1 Analog input, ADC: 0 – 10 V
The analog input can be used as the 4th digital input
BICO technology
Modular design for extremely flexible configuration
High switching frequencies for low-noise motor operation
Detailed status information and integrated message functions

Protection characteristics
Overvoltage/undervoltage protection
Overtemperature protection for the inverter
Ground fault protection
Short-circuit protection
i2t thermal motor protection
PTC for motor protection

Performance Characteristics
V/f Control
♦ Flux Current Control (FCC) for improved dynamic response and motor
♦ Multi-point V/f characteristic
Automatic restart
Flying restart
Slip compensation
Fast Current Limitation (FCL) for trip-free operation
Motor holding brake
Built-in DC injection brake
Compound braking to improve braking performance
Setpoint input via:
♦ Analog input
♦ Communication interface
♦ JOG function
♦ Motorized potentiometer
♦ Fixed frequencies

Ramp function generator
♦ With smoothing
♦ Without smoothing

Closed-loop control with proportional-integral controller function (PI)



Mechanical installation

♦ To ensure the safe operation of the equipment, it must be installed and commissioned by qualified personnel in full compliance with the warnings laid down in these operating instructions.
♦ Take particular note of the general and regional installation and safety regulations regarding work on dangerous voltage installations (e.g. EN 50178), as well as the relevant regulations regarding the correct use of tools and personal protective gear.
♦ The mains input, DC and motor terminals, can carry dangerous voltages even if the inverter is inoperative; wait 5 minutes to allow the unit to discharge after
switching off before carrying out any installation work.
♦ The inverters can be mounted adjacent to each other. If they are mounted on top of each other, however, a clearance of 100 mm has to be observed.
♦ IP20 protection is only against direct contact, always use these products within a protective cabinet.

Avoiding Electro-Magnetic Interference (EMI)
The inverters are designed to operate in an industrial environment where a high level of EMI can be expected. Usually, good installation practices will ensure safe and trouble-free operation. If you encounter problems, follow the guidelines stated below.

Action to Take
Ensure that all equipment in the cubicle is well grounded using short, thick grounding cable connected to a common star point or busbar
Make sure that any control equipment (such as a PLC) connected to the inverter is connected to the same ground or star point as the inverter via a short thick link.
Connect the return ground from the motors controlled by the inverters directly to the ground connection (PE) on the associated inverter
Flat conductors are preferred as they have lower impedance at higher frequencies
Terminate the ends of the cable neatly, ensuring that unscreened wires are as short as possible
Separate the control cables from the power cables as much as possible, using separate trunking, if necessary at 90º to each other.
Whenever possible, use screened leads for the connections to the control circuitry
Ensure that the contactors in the cubicle are suppressed, either with R-C suppressors for AC contactors or ‘flywheel’ diodes for DC contactors fitted to
the coils. Varistor suppressors are also effective. This is important when the contactors are controlled from the inverter relay
Use screened or armored cables for the motor connections and ground the screen at both ends using the cable clamps

Screening Methods
Gland Plate
The Gland Plate Kit is supplied as an option. It allows easy and efficient connection of the necessary screening. See the Gland Plate Installation Instructions contained on the Docu-CD.
Screening without a Gland Plate
Should a Gland Plate not be available, then the inverter can be screened using the methodology shown .



Manual & Datasheet

#FileDescriptionDate addedAdded byFile sizeDownloads
1 pdf MICROMASTER 420 0.12 kW – 11 kW MICROMASTER 420 0.12 kW – 11 kW
MICROMASTER 420 0.12 kW – 11 kW
09/01/2017 15:47Miss Long5 MB1310
2 pdf MICROMASTER 420 Inverters 0.12 kW to 11 kW MICROMASTER 420 Inverters 0.12 kW to 11 kW
MICROMASTER 420 Inverters 0.12 kW to 11 kW
09/01/2017 15:47Miss Long1 MB222
09/01/2017 15:48Miss Long9 MB578
4 pdf Siemens Micromaster 420 Manual Siemens Micromaster 420 Manual
09/01/2017 15:48Miss Long2 MB315
5 pdf Micromaster_420_Parameter List03/28/2020 22:10admin2 MB0

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