elmatador
Electrical
- Jun 10, 2009
- 22
We are currently inplementing a design with a backup diesel generator which is used to backup critical loads in a facility. The generator is a CAT C32 PMG 1MW Standby, 1.25MVA. The generator is coupled to a traditional ATS with open transition transfer. When utility power is lost, the ATS will signal the generator to start, once the generator is up and running then the ATS closes the emergency source breaker.
There are several small step down dry type transformers:
1. Step1: 6x45kVa(Secondary has no load on energization. Secondary Loads are on time delay staggered contactors. Load usage is about 50% of transformer)
2. Step1: 1x15kVA, 3x30kVA. These have primarily resistive loads with 50% usage
3. Step2: 2x100HP motors on wye delta starters with time delay staggered start.
4. Step1: 2x25kW, 2x10kW, 2x5kW, 2x15kW unit heaters. In winter conditions these could potentially start when generator comes online.
Please note the emergency breaker will not be closed before the generator is excited. The generator will see the Step1 loads all at once. My concern is the inrush currents experienced by the genset due to transformer energization. The dry type transformers likely have a 12x or greater inrush.
Is there anyway to determine if the generator can sustain the step1 loads without getting overloaded/tripped? The CAT sizing software uses steady state values so the inrush currents is not properly represented in the calculations. Do you see any potential concerns in the setup?
There are several small step down dry type transformers:
1. Step1: 6x45kVa(Secondary has no load on energization. Secondary Loads are on time delay staggered contactors. Load usage is about 50% of transformer)
2. Step1: 1x15kVA, 3x30kVA. These have primarily resistive loads with 50% usage
3. Step2: 2x100HP motors on wye delta starters with time delay staggered start.
4. Step1: 2x25kW, 2x10kW, 2x5kW, 2x15kW unit heaters. In winter conditions these could potentially start when generator comes online.
Please note the emergency breaker will not be closed before the generator is excited. The generator will see the Step1 loads all at once. My concern is the inrush currents experienced by the genset due to transformer energization. The dry type transformers likely have a 12x or greater inrush.
Is there anyway to determine if the generator can sustain the step1 loads without getting overloaded/tripped? The CAT sizing software uses steady state values so the inrush currents is not properly represented in the calculations. Do you see any potential concerns in the setup?