# Maximum Frequency that the Schneider SSP1D440BDT can sustain?

Hello I am trying to find information on the Maximum Frequency that the Schneider SSP1D440BDT can sustain without causing damage? Can anyone help with this?

Welcome to the forum.

For a pure resistive load there should be no limit to the input frequency as far as damaging the semiconductors goes.

However you will not not get correct switching if the input changes faster than the response time of the SSR.

The data sheet says the response time is 0.1ms.
F = 1/t so, 1/0.0001 = 10000 Hz = 10 kHz.

Although when using the maximum switching speed I’d be concerned it might not keep up over the full temperature range and as it ages. So I would keep the switching speed much slower probably less than 5 kHz.

4 Likes

Devices classified as “solid state relays” with a wide-range, low-level control input of this sort are generally intended for use in low-frequency switching applications where a mechanical relay might also serve.

While the indicated “response time” figures may appear to suggest that a switching frequency on the order of 5 kHz is possible (1/(TOn+TOff)), it should be understood that the internal switches will be spending much of this time in a linear mode of operation, in transit between their fully “on” and “off” states where power dissipation is substantially (~100x) increased compared to steady-state operation.

If only switching once every few seconds (or minutes, or hours) the power dissipation associated with a 0.1ms switching event averages out to nearly zero and can be neglected, but will quickly become dominant as switching frequencies increase. I wouldn’t plan on switching faster than about 1 Hz without carefully characterizing the device’s dynamic behaviors and making accommodations for increased power dissipation.

If the desire is to do some sort of higher-frequency PWM work, the typical approach would be to use dedicated FETs with a driver circuit capable of delivering the higher currents needed to shave a few decimal points off the transition times.

4 Likes

Is not specifying a maximum switching frequency when there actually is one a common fraud with high power SSR’s?

Sadly there are all too many companies that defraud users by not specifying important operating parameters for there components. If it was a consumer product it would be subject to consumer protection laws and the FTC could force them to give the specification.