I've built a flyback transformer by hand for a circuit I am making and after shorting the secondary I have found my leakage inductance is very high. The primary inductance is around 2 mH, while the leakage inductance is at 1.3 mH and it is supposed to be at max only 60 uH. I have made the transformer twice now with the same result and I can't figure out what is going on.

Primary turns: 143

Secondary turns: 6 trifilar

As requested I am providing more detail. My primary inductance is calculated by:

$$ Lp = Vin^20.5*Duty*eff/(Po*fs) $$

Vin = 135V, Duty=0.636, eff=0.72, Po = 10W, fs =137kHz

I need to have a target primary inductanced around 1900-2000 uH, and so I need to used a gapped core. The transformer construction given by PI designer is. Note there are 3 layers of tape between primary and secondary.

.

My Primary winding looks like this:

Shorted secondary to measure leakage:

Picture of core inside bobbin, there is a slight gap at the top which could potentially contribute:

The core material I am using is N27, core is gapped 0.17MM (recommended core gap from PI is 1.2 mm. Here is the data sheet

I've built a flyback transformer by hand for a circuit I am making and after shorting the secondary I have found my leakage inductance is very high. The primary inductance is around 2 mH, while the leakage inductance is at 1.3 mH and it is supposed to be at max only 60 uH. I have made the transformer twice now with the same result and I can't figure out what is going on.

Primary turns: 143

Secondary turns: 6 trifilar

As requested I am providing more detail. My primary inductance is calculated by:

$$ Lp = Vin^20.5*Duty*eff/(Po*fs) $$

Vin = 135V, Duty=0.636, eff=0.72, Po = 10W, fs =137kHz

I need to have a target primary inductanced around 1900-2000 uH, and so I need to used a gapped core. The transformer construction given by PI designer is. Note there are 3 layers of tape between primary and secondary.

.

My Primary winding looks like this:

Shorted secondary to measure leakage:

Picture of core inside bobbin, there is a slight gap at the top which could potentially contribute:

The core material I am using is N27, core is gapped 0.17MM (recommended core gap from PI is 1.2 mm. Here is the data sheet The measurement was made on Proster 3M4070 LCR meter, accuracy should be off by roughly +/- 5 uH. The wires used for the core were not triple insulated, they are some wires I got off Amazon from BNTechGO

I've built a flyback transformer by hand for a circuit I am making and after shorting the secondary I have found my leakage inductance is very high. The primary inductance is around 2 mH, while the leakage inductance is at 1.3 mH and it is supposed to be at max only 60 uH. I have made the transformer twice now with the same result and I can't figure out what is going on.

Primary turns: 143

Secondary turns: 6 trifilar

I've built a flyback transformer by hand for a circuit I am making and after shorting the secondary I have found my leakage inductance is very high. The primary inductance is around 2 mH, while the leakage inductance is at 1.3 mH and it is supposed to be at max only 60 uH. I have made the transformer twice now with the same result and I can't figure out what is going on.

Primary turns: 143

Secondary turns: 6 trifilar

As requested I am providing more detail. My primary inductance is calculated by:

$$ Lp = Vin^20.5*Duty*eff/(Po*fs) $$

Vin = 135V, Duty=0.636, eff=0.72, Po = 10W, fs =137kHz

I need to have a target primary inductanced around 1900-2000 uH, and so I need to used a gapped core. The transformer construction given by PI designer is. Note there are 3 layers of tape between primary and secondary.

.

My Primary winding looks like this:

Shorted secondary to measure leakage:

Picture of core inside bobbin, there is a slight gap at the top which could potentially contribute:

The core material I am using is N27, core is gapped 0.17MM (recommended core gap from PI is 1.2 mm. Here is the data sheet