A valve assembly has a valve body defining a chamber with a controlled outlet. The optical zoom lens module satisfies the formula: 12<TTLFW<16, and 6<F1F<8, where TTL is the total length of the optical zoom lens module, FW is the smallest effective focal length of the optical zoom lens module, F1 is the effective focal length of the first lens group, and F is the effective focal length of the optical zoom lens module. A magnet mounting arrangement for a rotor or a stator of an electrical machine and a wind turbine with a generator including a rotor and a stator and such a magnet mounting arrangement are also provided.