Frequency inverters

• Smooth start and stop; by allowing motors to start and stop gradually, you reduce mechanical shocks and reduce wear. As a result, you reduce the peak load on the mains during start-up in particular.
• Variable speed control; you can infinitely adjust the speed of a motor. This is especially important in applications where the motor speed is tuned to changing conditions.
• Energy-saving;  because the motor does not constantly run at full speed, but is tuned to the necessary load, you can save energy.
• Improved precision; by precisely controlling motor performance, you can optimise processes and improve product quality.
• Preventing overload; an AC drive can protect motors from overload and damage with the right settings.
• Reverse direction of rotation; All our AC drives can reverse the direction of rotation of the motor. This can be useful in certain situations. 
• PM control; they are also suitable for controlling permanent magnet motors.

The ME300 and MS300 series AC drives are compact and easy to set up. The drives have a control panel as standard. The drives have an analogue input for connecting a potentiometer or an analogue signal from, for example, a PLC.

There are 16 adjustable presets in the drive via 4 digital inputs. The drives can be controlled with hard contacts, but also via a PLC output (NPN or PNP), adjustable via a dip switch.

The Delta VFD-E series has reached end-of-life. For new machines and replacements of existing drives, we recommend the Delta MS300 series.

The MS300 is not a direct replacement for the VFD-E. The drive is more compact, supports more motor types, and has built-in features that were more limited or optional on the VFD-E. These include STO, USB, modern communication cards, and support for both IM and PM motors.

When replacing a drive, it’s important to check the dimensions, connections, parameters, and communication capabilities, as these may differ. Especially with existing machines, it’s wise to look beyond just power and voltage.

Why is Delta discontinuing the VFD-E?

For many years, the VFD-E was a compact drive for simple to medium-duty applications. It was well-suited for low power ratings, featuring an IP20 enclosure, modular expansions, and a built-in PLC function for simple ladder logic. 

What does the MS300 do better than the VFD-E?

More compact design

The MS300 is smaller than previous drives, with a size reduction of up to 40%. This is practical for panel building, retrofits, and machines where cabinet space is limited. 

• More space in the cabinet
• Easier to install multiple drives side by side
• Less hassle when expanding or replacing

Note: A more compact design does not automatically mean it will fit the same mounting holes. When replacing a drive, always check the footprint.

Support for IM and PM motors

The VFD-E is best known as a compact drive for standard induction motors. The MS300 supports open-loop control of both IM and PM motors. 

This makes the MS300 more versatile. For example, in compact machines, retrofit projects, or applications where a more energy-efficient PM motor is used.

STO Available as Standard

The MS300 features Safe Torque Off (STO). This is a key difference for machines where safety circuits play a role. With STO, torque can be safely shut off without always having to interrupt the power supply to the drive.

For machine builders and engineers, this is particularly useful in:

• emergency stop circuits
• guards
• service modes
• CE compliance modifications or overhauls

The exact application depends on the machine’s safety design. STO is not a complete safety system in and of itself.

More communication options

The VFD-E featured optional fieldbus modules, including those for DeviceNet, Profibus, LonWorks, and CANopen. 

The MS300 has a built-in communication slot for various communication cards, including CANopen, Profibus, DeviceNet, MODBUS TCP, and EtherNet/IP. 

Machines are often connected to PLCs, HMIs, data logging systems, or maintenance systems. In such cases, you want to be able to read not only start/stop and analog setpoints, but also error codes, status, current, frequency, and parameters.

USB for Parameter Setting and Data Transfer

The MS300 is equipped with a USB port that allows parameters to be easily uploaded and downloaded without the controller needing to be connected to mains power. 

This saves time during mass production, service, and replacement. Parameters can be copied or checked more quickly; when dealing with multiple identical machines, you don’t have to set everything manually via the keypad. 

The keypad is standard on the MS300. On the VFD-E, it was an optional accessory.

Built-in PLC function remains available

The VFD-E had a built-in PLC function for simple ladder logic. The MS300 has a built-in PLC function with a 2K-step capacity. 
This is useful for small local functions, such as simple switching logic, a start condition, a timer, or a pump/fan function—all without the need for a separate small PLC.

For more complex machine control, a separate PLC usually provides a clearer overview.

Higher overload capacity and built-in brake chopper

The MS300 features a dual-rating design: 120% for 60 seconds in Normal Duty mode and 150% for 60 seconds in Heavy Duty mode. It also includes a built-in brake chopper.

This is relevant for applications with higher starting torques or braking energy. Examples include material handling, woodworking, packaging machines, or machines with short cycle times.

Always check whether an external braking resistor is required. This depends on the load, cycle time, and braking time.

Higher frequency ranges available

The VFD-E has an output frequency range of 0.1 to 600 Hz.
The standard MS300 models go up to 599 Hz. The high-speed models go up to 1500 Hz in V/f control. 

For standard applications, this makes little difference. For special spindles or high-speed applications, it can be relevant. Key factors here are the motor type, cooling, bearings, and application.

What should you look out for when replacing a drive?

When replacing a VFD-E with an MS300, you should at least check the following:

• supply voltage
• motor power and rated motor current
• overload capacity, duty cycle, and braking behavior
• mounting dimensions
• cooling and clearance in the enclosure
• I/O connections
• parameter settings
• Communication protocol
• EMC filter and cabling
• Safety function, especially for STO
• Existing accessories, such as keypad, expansion cards, and braking resistor

When is the MS300 a good replacement?

The MS300 is particularly suitable for compact machine building and retrofit applications where the VFD-E was previously used.

Examples include:

• conveyor belts
• small pumps
• fans
• packaging machines
• woodworking machines
• simple machine shafts
• Applications with standard motor control
• systems requiring communication with a PLC or HMI 

For heavy-duty applications, high dynamics, or specific process control, another Delta series may be a better fit. For example, the C2000 or MH300. It depends on the application.

Help with selection or replacement

When replacing a VFD-E, it’s important to look beyond just the model number. We’d like to first check what the drive does in the machine.

What do we need for that:

• model number of the current VFD-E
• motor specifications from the nameplate
• supply voltage
• machine application
• I/O used
• Communication protocol (if applicable)
• Photo of the connections or the schematic
• Current parameter list, if available

Based on this information, we can determine which MS300 model is suitable and where adjustments to the wiring or parameters are needed.

Would you like us to take a look? Please provide the information above via this form, by email, or via WhatsApp.

The IP rating, ‘International protection’, is an accurate method of indicating the degrees of protection of enclosures. This IP rating indicates the extent to which, for example, an AC drive is resistant to water and dust. Depending on the situation in which it is used, you need an IP Class that provides adequate protection.

The values are listed below:

We can supply AC drives from IP20 to IP66. Frequently used for pumps is the CFP series with IP55 housing. This can easily be installed outside a cabinet.

Veel elektromotoren hebben tegenwoordig een ingebouwde PTC, De weerstand van deze PTC word hoger als de tempratuur van de motor toeneemt. In tegenstelling tot een PT100 kun je niet exact de tempratuur meten. De regelaar heeft een analoge ingang waar de PTC op binnenkomt. Wanneer deze een bepaalde waarde bereikt schakelt deze de motor af of geeft hier een melding van op het display.

Many electric motors nowadays have a built-in PTC. The resistance of this PTC increases when the temperature of the motor increases. Unlike a PT100, you cannot measure the temperature exactly. The controller has an analogue input where the PTC enters. When it reaches a certain value, it switches off the motor or gives a message on the display.

Schematic diagram

By connecting Figure 1: Electrical schematic, the PTC can almost be put into operation. For this, some parameters still need to be changed. More about this is described in Parameters.
AFM is the analogue output, ACI is the analogue input, ACM is ground. The AFM2 sends out a constant current.
To get everything working properly, 2 dipswitches need to be flipped for an overview. The dipswitch of ACI has to be set to 0/4-20mA . This means that the ACI measures current. The AFM's dipswitch should be set to 0/4-20mA . This means that the analogue output emits a current.

*optional parameter

The ACI input should be set as a PTC input. If the value of this input exceeds parameter 06-30, the motor switches off. Whether the motor switches off depends on parameter 06-29.
To monitor the input, it is possible to display this value on the start screen of the drive. You can do this by setting parameter 00-04 to 12. This value is in percent.
The switch-off point can be shifted using parameter 06-30. At 50%, the outside of the motor is about 75-85 °C.
Due to the characteristics of the PTC, the difference between 50% and 51% is much greater than between 30% and 35%.

Many electric motors today have a built-in PTC, the resistance of this PTC increases as the temperature of the motor increases. Unlike a PT100, you cannot measure the temperature exactly. The MS300 has an analogue input where the PTC enters. When it reaches a certain value, it switches off the motor or gives a message on the display. 

Diagram 

By connecting Figure 1: Electrical schematic, the PTC can almost be put into operation. For this, some parameters still need to be changed. More about this is described in Parameters. 

AFM is the analogue output, ACI is the analogue input, ACM is ground. The AFM sends out a constant current. 

To get everything working properly, 2 dipswitches have to be switched for an overview see Figure 2: Dipswitch overview. The ACI dipswitch should be to the left. This means that ACI measures current. The AFM's dipswitch should be set to the right. This means that the analogue output emits a fixed current. 

*optional parameter 
 

The ACI input should be set as a PTC input. If the value of this input exceeds parameter 06-30, the motor switches off. Whether the motor switches off depends on parameter 06-29. 
To monitor the input, it is possible to display this value on the start screen of the drive. You can do this by setting parameter 00-04 to 12. This value is in percent. 
The switch-off point can be shifted using parameter 06-30. At 50%, the outside of the motor is about 75-85 °C. 
Due to the characteristics of the PTC, the difference between 50% and 51% is much greater than between 30% and 35%.

What is the 87Hz principle and when do you apply it ?

The 87Hz principle (also called the √3 principle) can be applied to maintain torque at a frequency higher than the motor's base frequency.
A standard AC motor 50Hz/400V (connected in star) delivers its rated torque up to 50Hz. At frequencies above 50Hz, torque decreases.
Up to a frequency of 50Hz, frequency and voltage are controlled, from 50Hz onwards, only frequency is increased and voltage remains 400V.
If a voltage of 400V is output at 50Hz, then at 25Hz the output voltage is 200V. The ratio of voltage to frequency is then constant (400/50 = 8V/Hz and 200/25 = 8V/Hz).
If the frequency is increased further to e.g. 80Hz, then, since the voltage is not increased further, this ratio becomes 400/80 = 5V/Hz.
This causes the motor to go into the so-called field weakening mode and the torque decreases inversely with speed. For example, when the speed doubles (100Hz), the torque is half.
In many cases, the lower torque is not such a problem, but sometimes it is important to maintain nominal torque at frequencies above 50Hz. In such cases, you can apply the √3 principle.

What are the conditions for applying this principle ?

In order to use a motor and frequency converter in this way, there are some conditions:

• The motor must be wound for 230V_delta/400V_star and be suitable for 87Hz.
• The motor (and the implement connected to it) must be mechanically suitable for the higher speeds. (Almost always a 4-pole-1500 rpm motor is used for this purpose).
• Operation above 50 Hz is for shorter periods.
• Because of additional losses in the motor, the thermal load is higher. We recommend monitoring the motor for temperature, e.g. with PTCs. Depending on the application, in certain cases it may be better to choose the motor one or two steps larger.
• The AC drive should be suitable for the current at triangular connection of the motor. For example, for a 2.2kW motor, the inverter must become √3 x 2.2kW = 3.81kW = 4kW.

How do you connect the motor ?

By connecting the motor in triangle and setting the inverter differently, the frequency can be increased to 87Hz while still delivering almost the rated torque. 
The larger control range gives the machine or implement more flexibility. A 4-pole motor with a nominal speed of e.g. 1440 rpm at 50 Hz, then turns 2505 rpm at 87 Hz.

How is the frequency inverter set?

The frequency converter is set so that the voltage-frequency ratio remains constant up to a frequency of 87 Hz.
To do this, the base frequency of the inverter is set to 87Hz. This means that the voltage of 400V is reached at 87Hz. It follows that at a frequency of 50Hz, the voltage is 230V.
With this technique, frequency and voltage are controlled over the entire range 0 - 87Hz. The ratio of voltage to frequency is constant over this entire range and so the torque also remains constant up to 87Hz.

Parameters to be set:

This principle is usually applied to 50Hz motors, for 60Hz motors this √3 principle can also be used. Then the base frequency is set to 60 x √3 =104Hz.