Calculations and Definitions

Smartblick performs calculations at various places in the Dashboard. You can find an overview of these here along with important definitions:

Power on Time

• Anytime the mains connection sensor detects that the machine is turned on

Active Time

• Anytimethe sensor you have selected in the machine settings detects activity

Unplanned Downtime

• Anytime the selected sensor does not detect activity and the user has not manually entered a Planned Downtime label

Efficiency

• Active time divided by (active time + Unplanned downtime). Planned downtimes are excluded.

Machine Data

We use contactless split core current transformers for current measurements on current-carrying motor cables in CNC machines in both the AC and DC ranges.

• Three-phase power system mains connection: 230Vrms / 50Hz U12=U13=U23=400V

• Number of motor pole pairs: 2

• The maximum motor speed is up to 18,000rpm with a maximum motor current of 100A.

• As we only measure current on the one external current line of the 3-phase mains connection, we assume that currents of the all three external current lines are equal (excluding phase shifts) and the power system is balanced.

• The power factor cos(φ)=active/apparent power = 0.98 (default for most machines)

Using these assumptions, combined with the Current data points, we can determine the RPM and Load.

RPM

We measure the rotations per minute of the spindle motors through the calculated current frequency and the given number of motor pole pairs:

RPM = f[Hz] * 60[s/minute] / 2

Load

We calculated the Active power [W] using the following simplification:

P = 3 * Irms * U12 * cos(φ),

P = Ipk * U12 * cos(φ) * 3/√2,

P = Ipk * U1N * cos(φ) * 3√3/√2,

P = Ipk * U1N * cos(φ) * 3√6/2,

where U12 and U1N are:

Irms=Ipk/√2;

U1N=230Vrms;

U12=U1N√3=400Vrms.

You may notice that the Spindle load is often higher than the Main connection load, this happens when the Frequency converter increases the current by decreasing the voltage. As we are not able to measure the voltage, all calculations use the assumption above.