Question 1

How to set up a compressor control with a MH300 frequency inverter

Accepted Answer

Energy savings from a refrigeration compressor

By connecting a frequency inverter to a refrigeration compressor, you can adjust the cooling capacity according to the system's cooling demand. This can result in significant energy savings. By varying the compressor speed based on the cooling demand, stable system pressure is created. This also reduces maintenance costs.
Because a frequency controller can be used to control the compressor speed higher than the mains frequency, in many cases the compressor cooling capacity can be increased by approx. 20 %.

Basic connections

Below are some important settings to enable Compressor control based on pressure. It is important which pressure sensor is used; 0-10volt or 4-20mA and two-wire or three-wire. Most common is 4-20mA in a two-wire version.

1. Connect power supply of the sensor to +10V and the signal side to the ACI.

2. Create a start signal between the DCM and Mi1.

signaal tussen de DCM en Mi1. — Signaal tussen de DCM en Mi1.

3 Settings

To pressurise a system, you need to enter a wish value indicating the system to be controlled. The actual system pressure is then fed back via the pressure sensor, with which the frequency controller will then try to adjust the compressor speed to bring this pressure into line with the wish value. The most commonly used method is to set the wish value on the drive's display. As the MH300 does not have a text display, you can only work in Hz or % here. With a pressure control, it is convenient to work in %. Set 00-25 to 0021 The value F in the display then becomes % of 0-100.0.

You can then set the desired pressure between 0-100.0 percent( is 0- max. sensor pressure).

To get the sensor value in the PID you have to set parameter 03-01 to 5( PID feedback)

To monitor this value it is useful to set 00-04 to 10( PID feedback monitor)in The User defined display ‘U’ you can then monitor the sensor value.

Furthermore, the PID operation must be activated.(08-00) For a compressor, you want the speed to increase if the feedback value is lower than the setpoint ( negative feedback) and the value comes in via the analogue input so setting 1
Furthermore, it is important for the system that the control will run stably in case of deviation in the sensor value. For this, 08-01 (Gain) 08-02 (Integration time) and possibly 08-03( Differentiation time) must be set to the system's response. This depends entirely on the system and the power of the compressor.

Question 2

How to apply the 87Hz principle to an inverter?

Accepted Answer

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.

Frequentie_koppelverloop — Frequency - Torque drift

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.

Question 3

What are IP ratings and why do you use IP55 or 66?

Accepted Answer

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.

Question 4

How do I set up a PID control?

Accepted Answer

Description how to set up the Delta C2000 for pressure feedback with a 0-20 mA sensor. 0-40 Bar.

1. Sensor connections

2. Connecting start/stop signal to FWD and DCM . bridge from +24 V to Com.

Parameter setting :

00-00 9 reset to 50 Hz.
00-04 12 diplay the value of the ACI input
00-21 1 start/stop via terminals
00-25 0161 reading in BAR 1 decimal place
00-26 0400 maximum setting is 40.0 Bar.
01-12 at will acceleration time approx. 3 - 5 sec.
01-13 discretionary deceleration time approx. 3-5 sec.
03-00 0 AVI no function
03-01 5 ACI is PID feedback
05-01 motor current type plate
06-27 1 thermal protection switched on for standard motor
08-00 1 PID negative feedback on analogue input
08-01 at will proportional gain higher is faster reaction in case of deviation
08-02 at will integration time damping for feedback higher is longer damping time.

Apply power to the controller and look at the display first . In the display for F you should see a value in Bar or a value in %. If it says 0 and the sensor has pressure, it is probably connected the wrong way round. If this value goes along with the pressure on the sensor, we know that the sensor is connected correctly.

Now set :

00-04 10 diplay the value of PID feedback coupling.
You should now see at the readout U again a value however between 0-40 Bar.
If that is correct then the PID feedback is also working. Now run the pump and see if the control responds properly otherwise adjust 08-01 and 08-02.

Question 5

How to dismantle an encoder plug

Accepted Answer

Description how to disassemble the encoder plug for passing through a cable gland and then reassemble it.

Unscrew the connector.
Using a small screwdriver, gently push the two white parts apart. Now gently push the contact pins back through the latch.
Remove all connector parts from the cable and feed the pins through the swivel.
Put all connector parts back on the cable. First the sleeve then the strain relief, rubber part. Fold the shield back around the black plastic part and lock it with the crown. Put the white parts back together up to the first lock. And then push the pins back into the correct holes
1 - Pink 2 - grey 3 - yellow 4 - green 8 - white 9 - brown.
Press the white parts back together in the locking holes. If this does not go well check whether all pins are inserted deep enough.
Now screw the connector back together.

Question 6

How can you calculate the Gear ratio of a servo motor?

Accepted Answer

In the xls file ASDA-Gear-ratio-calculating created by us, you can easily perform the calculation per series.

Question 7

How do I adjust the gear ratio from my Codesys programme?

Accepted Answer

Using the SMC_ChangeGearingRatio function block, the gear ratio and drive type can be changed from within the programme.

Overbrengingsverhouding_ChangeGearing_ratio

After execution, the axis must be restarted using SMC3_ReinitDrive to ensure that all variables are initialised correctly.

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