03 · GENERATORS
Generators
Good backup power is tested before it is needed. We connect generators to new and existing sites, install transfer boards and automatic transfer switches (ATS), test the installation afterwards, and maintain the system over time.
03 · SIMULATOR
What happens the moment the power goes out?
Press "Power outage" and watch the automatic transfer, step by step.
Powered
Supplied by grid
Which generator do you need?
The list includes motors: direct-on-line starting current is about 6 times the running current. We check it in the load survey.
03 · CAPABILITIES
What we do
Connection & installation
Connection design, cabling and boards, installed by our own crew.
Automatic transfer
Transfer boards and ATS that switch to backup with no manual action.
Testing
Electrical testing after installation and periodic transfer tests.
Maintenance
Routine maintenance so the generator works on the day it is needed.
03 · IN DEPTH
In depth
What happens in the seconds after the power goes out
When the grid fails, the automatic transfer switch (ATS) does not react at once. First it waits out a short start delay, so that a momentary blip does not start the generator. Then the generator cranks, and the controller waits for the voltage and frequency to stabilise. Only then does the switch move the building to the generator, in an open transition: break before make, off the grid first and only then onto the generator, as the Israeli generator regulations require. From that moment the building runs on the generator.
In the simulator above, the settings are 2 seconds to detect, 4 to crank, 3 to stabilise and half a second to transfer: 9.5 seconds without power. Under US standards, emergency systems must be back on supply within 10 seconds: that is Type 10 in NFPA 110, and the requirement of the US electrical code, NEC 700.12. For legally required standby systems, NEC 701.12 allows up to 60 seconds.
When the grid returns, the controller waits several minutes to make sure it is stable (5 minutes in the simulator), transfers the building back, and lets the generator run unloaded to cool down before it stops. A closed transition, with both sources in parallel for under 100 ms, avoids the short break on the way back, but it needs the utility’s approval. In Israel, a solar system must not run in parallel with a generator that was not designed for it, and its inverters reconnect only after at least 5 minutes of stable grid.
Sources: NFPA 110 · IEC 60947-6-1 · Israeli Electricity (Installation of Low-Voltage Generators) Regulations, 1987
kW, kVA and motors: choosing a generator size
A generator is rated in kVA, apparent power, while loads are measured in kW, real power. The ratio between them is the power factor, and the calculation takes 0.8: kVA = kW ÷ 0.8. Add a 25% margin and round up to the next standard rating. That is what the sizing card in the simulator above does once you tick the loads that must keep running in an outage.
Motors need a separate check. Started direct-on-line, a motor draws about 6 times its full-load (rated) current and the generator’s voltage dips: roughly x″d·S ÷ (S_gen + x″d·S), with S the starting kVA and x″d the generator’s subtransient reactance. With x″d at 0.15, a typical value according to manufacturer data, a 75 kW motor at 400 V dips the voltage by about 23% on a 300 kVA generator and about 15% on a 500 kVA one. A star-delta starter cuts the starting kVA to about a third; a variable-frequency drive reduces it too, but loads the alternator with harmonics that the sizing must allow for.
The sizing card also checks the largest motor on the list and picks a generator that keeps the dip within 35%. Sensitive equipment may need a tighter limit, and ISO 8528-5 defines performance classes for that. ISO 8528-1 also defines the types of rating: emergency standby power (ESP) for up to 200 hours a year, prime power (PRP) for unlimited hours at a variable load, and continuous power (COP) for a constant load. For a generator that only backs up outages, the ESP rating is the relevant one.
Sources: ISO 8528-1 · ISO 8528-5
Maintenance: an untested generator may not start when needed
A standby generator spends most of its life standing still, so faults can surface just when the power fails. A fixed routine reduces that risk: periodic test runs under load, periodic visual inspection of the engine, cables and panel, and an annual service with oil and filter changes and checks of the coolant and belts. The Israeli generator regulations also require an inspection by a licensed electrical inspector before first use, after changes, and periodically.
Three things need special attention on a generator that mostly stands idle: the starting battery, which loses capacity over the years; the diesel, which degrades in the tank through water and microbial growth; and the transfer switch, which must be tested to confirm that it really moves the building to the generator and back to the grid. Every test, service and fault goes into a maintenance log, so a trend can be spotted before it turns into a failure.
In the simulator above, the “Periodic test” button starts the generator without load while the building stays on the grid. Such a test confirms that the set starts and stabilises, but only a run under load, or a real transfer test, confirms that it can also carry the building. The US standard NFPA 110 sets out a programme of routine maintenance and testing for emergency systems; we set the frequency and load of the tests by the manufacturer’s instructions, the Israeli regulations and the nature of the building.
Sources: NFPA 110 · Israeli Electricity (Installation of Low-Voltage Generators) Regulations, 1987
03 · PROCESS
How it works
- 01
Load survey
Mapping the loads that need backup and the connection size.
- 02
Connection design
Design of the transfer board, protection and cabling.
- 03
Installation
Generator connection and transfer-switch installation.
- 04
Test & start-up
Electrical test, transfer trial and start-up.
- 05
Maintenance
Periodic tests and routine service.
03 · CLIENTS
Who it is for
- Clinics and institutions
- Public buildings
- Retail and industry
- Agriculture
03 · FAQ
Frequently asked questions
How long is the building without power before the generator takes over?
With the simulator’s default settings, 9.5 seconds: detecting the outage, cranking, stabilising and transferring. Under US standards, emergency systems must be back on supply within 10 seconds, Type 10 in NFPA 110. Equipment that must not stop even for a moment, such as servers or some medical devices, needs a UPS to bridge those seconds.
Why is an automatic transfer switch (ATS) needed?
The transfer switch keeps the generator from being connected to the grid: it disconnects the building from the grid before connecting it to the generator. That way the generator cannot feed power back into utility lines that crews may be working on. It also does the whole transfer by itself, with no one having to come and operate switches, and returns the building to the grid once supply is back and stable.
How do you know what size generator you need?
It starts with a load survey: what must keep running in an outage, and how many kW it draws. Then come the motors, such as air conditioning, pumps and lifts, and how they start, because a motor started direct-on-line draws about 6 times its full-load (rated) current and can end up setting the generator size. The sizing card in the simulator above lets you tick loads and get a first estimate.
Can a generator serve a building that has solar?
Yes, with a proper design. The solar system must not run in parallel with a generator that was not designed for it: solar output above the building’s consumption could push power into the generator and damage it. So the design includes interlocks and controls that disconnect the inverters, or limit their output, while the building runs on the generator.
CONTACT
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