Testing a motor for durability: how we test dynamic UPSs

Hello, Habr! My name is Victor, I am the chief power engineer at the Udomlya mega-data center. My colleagues have already shown how we organize a guaranteed power supply to the data center using diesel generators and regularly check their performance. But besides the diesel generator set, there is other equipment that can simultaneously provide guaranteed power supply and uninterruptible power supply. We are talking about diesel dynamic UPS (DIBP). Such installations are in our mega-data center, and we have already talked a little about their arrangement in a tour of the data center.

Today I will show you how we test DIBP diesel engines to be sure of their reliability.

A little about the device DIBP

DIBP combines the functions of several devices in one: one unit replaces the system of diesel generator sets, static UPS and batteries. True, they roar more strongly: the noise level from classic DIBPs is comparable to the noise from a hammer drill.

DIBP room.  I do not recommend going here without hearing protection.
DIBP room. I do not recommend going here without hearing protection.

The power supply circuit with DIBP is built a little differently. The city power supply from step-down transformers goes in two independent routes to the low voltage switchgear (LVDG). And from there, through the DIBP, electricity goes directly to IT and engineering equipment. If the power supply from the city is lost, the DIBP will instantly take all the load on itself.

Power supply diagram of the Udomlya mega-data center.
Power supply diagram of the Udomlya mega-data center.

In Udomlya we have Euro Diesel rotary-type uninterruptible power supplies. In such DIBPs, the diesel engine is connected to an AC static generator by means of an electromagnetic clutch. This generator consists of a kinetic energy accumulator and a synchronous reversible electric machine.

The electric machine can operate in the mode of an electric motor and a generator. While the DIBP operates on city power, the electric machine works as an engine and stores kinetic energy in the battery. If the city power is lost, the stored energy is released in the opposite direction and allows the electric machine to provide power to the data center. This same energy starts the diesel and helps it to reach the operating frequency. The diesel starts up in one minute, and then it provides power to the data center and accumulates energy in the battery.

This is how the switching circuit looks briefly:

Annual maintenance of the DIBP at the Udomlya data center is divided into stages and is carried out several times throughout the year. This phased schedule helps us reduce the downtime of the RIBP during maintenance. We service the electrical part separately: we check the electromagnetic clutch, we service the kinetic energy accumulator and the reversible synchronous electric machine. We separately check and test the DIBP diesel engine. We carried out such an annual maintenance of the diesel engine in February, I will tell you more about it.

Diesel Engine Test Plan

Our service engineers and vendor engineers are involved in diesel testing. During maintenance, we control several parameters:

  • we check the rubber hoses and the tension of the alternator belts,

  • check the freezing point and coolant level,

  • we control the serviceability of the pre-heaters and the condition of the engine cooling radiator,

  • check the battery charge voltage, electrolyte level and density,

  • we measure the residual capacity and voltage of the battery,

  • change filters and engine oil,

  • we carry out a test of the DIBP diesel engine at a load of 100%.

Thanks to such a test program, we not only guarantee that the DIBP will not fail at a critical moment, but also simultaneously monitor the operation of the ventilation and fuel supply systems.

The test start of the DIBP motor is carried out at one hundred percent load. When we talked about testing DGU last time, we showed a version of testing with a real load. We will service and test the DIBP motor under an equivalent load. Let’s create it using load modules: these electromechanical devices simulate the load of the required power.

This testing method is the most rational for our case. First, we are not dependent on third-party loads. A data center is a living organism, and the amount of IT workloads can vary. Secondly, the test does not affect the client equipment and engineering systems. Even if something goes wrong during the test, the power supply of the client equipment and engineering systems of the data center will not be affected.

Preparing for testing

Alert… 7 calendar days before the start of maintenance, the technical support service warns about the work of the data center customers and the operation service. Be sure to indicate the time and sequence of testing. For 6 installed DIBPs, we have 6 days.

Ordering load modules… Before the start of maintenance, consumables and load modules are supplied to the data center. We use 2 modules, 1 mW each.

Switching the RIBP and connecting the load… We start maintenance by stopping the DIBP and connecting the modules. All switching is performed on two DIBP boards: control and power.

The control panel is equipped with a touch panel and allows you to control the operation of the DIBP using automatic switches located inside the power panel. Special keys on the control panel allow you to change the operating modes.

Touch panel on the RIBP control panel.
Touch panel on the RIBP control panel.

The load modules are connected once, since all the power panels of the DIBP are connected to each other by a conductor. Later, we will apply the load to each DIBP using the automatic switches on the power panel of the DIBP.

Routine work before test run

The first steps of the maintenance plan must be performed with the generator turned off. Therefore, we will first take the unit for repair.

  1. Let’s move on to the RIBP control panel. On the display on the left, we see that the power supply of the IT equipment and engineering systems of the data center is going according to the standard scheme. The diagram shows the circuit breakers in the circuit: QD1, QD2 are on, QD3 is off.

    On the right we see the key in the “Load protected” position. This means that the uninterrupted operation of all equipment is protected by a UPS. The electric machine operates in electric motor mode, the battery accumulates kinetic energy, everything is fine:

  2. On the right, with the help of the upper key, we transfer the operating mode to the bypass mechanism, or bypass (we have already talked about it in one of the articles). With its help, the equipment supplied from the DIBP is immediately transferred to the power supply from the city, bypassing the installation, and the generator is disconnected from the network. Now in the diagram we see that the switches QD1 and QD2 are off, QD3 is on:

  3. So that no one accidentally turns on the unit and jeopardizes the performance of routine maintenance, we transfer the QD1, QD2 switches to the repair position on the power panel of the DIBP:

After stopping the drive and generator, we carry out routine maintenance according to the test plan: we check belts, fluids, filters, all systems and assemblies.

Control panel of the stopped DIBP.
Control panel of the stopped DIBP.

Test start of the DIBP motor under load

After all the manipulations according to the maintenance plan, we proceed to the final stage – the test of the diesel engine under 100% load.

  1. On the power panel, put the QD1, QD2 switches back into the operating position. We move the control key to the “CONTROL VIA HMI” position. The buttons on the touch panel become active.

  2. We turn on the machine in the “BYPASS-RUN” mode. We see in the diagram that QD1 is on, QD2 is off.

    Now the generator is powered by the city grid and works like an electric motor, spinning the kinetic energy accumulator. The IT equipment and utility systems in the data center are by-passed through the QD3.

  3. We transfer the DIBP to the testing mode: open the control panel and set the “TEST KS” switch to position 1.

    In test mode, the QD2 switch is blocked. “KS TEST MODE…” appears on the panel screen.

  4. The next step is to connect the load modules to the generator buses.

    At the very beginning, we connected the load modules to the board. Now we turn on the load using the QDL circuit breakers in the power panels of the DIBP. We carry out this operation in manual mode: roll the QDL switch into the operating position, unlock it with a key, charge the spring and turn it on.

  5. To start the DIBP engine, we carry out a test mains failure. Press the buttons “NETWORK FAILURE” and “FORCE” on the control panel.

  6. The engine is in operation, the reversible electric machine in generator mode supplies the load modules, the city grid is disconnected.

    DIBP operates in generator mode.
    DIBP operates in generator mode.
  7. Now we raise the load to the required values. For this, we use switches on the panels of the load modules. On the DIBP control panel, we see that this parameter has reached 1764.1 kW.

    We look at the operation of the DIBP under load.
    We look at the operation of the DIBP under load.

The engine runs in this mode for about 2 hours. During the test, we control several parameters of the RIBP:

  • bearing temperature,

  • shaft rotation speed,

  • oil pressure,

  • indoor air and temperature of liquids,

  • battery charge.

All parameters are shown on the display.
All parameters are shown on the display.

Electrical parameters are also monitored: frequency, power and voltage.

Freezing results and switching back

After the tests, we turn off the load modules in reverse order, take the DIBP out of the test mode and turn the key on the control panel to the “LOAD PROTECTED” position. The switching scenario has been worked out, no power outages should interfere with the work of the data center.

Based on the test results, we indicate all the parameters obtained in the protocols. DIBP proceeds to the next round of maintenance according to the annual schedule.

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